Arbutils/extern/backward.hpp

/*
* backward.hpp
* Copyright 2013 Google Inc. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/

#ifndef H_6B9572DA_A64B_49E6_B234_051480991C89
#define H_6B9572DA_A64B_49E6_B234_051480991C89

#ifndef __cplusplus
#error "It's not going to compile without a C++ compiler..."
#endif

#if defined(BACKWARD_CXX11)
#elif defined(BACKWARD_CXX98)
#else
#if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
#define BACKWARD_CXX11
#define BACKWARD_ATLEAST_CXX11
#define BACKWARD_ATLEAST_CXX98
#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
#define BACKWARD_ATLEAST_CXX17
#endif
#else
#define BACKWARD_CXX98
#define BACKWARD_ATLEAST_CXX98
#endif
#endif

// You can define one of the following (or leave it to the auto-detection):
//
// #define BACKWARD_SYSTEM_LINUX
//	- specialization for linux
//
// #define BACKWARD_SYSTEM_DARWIN
//	- specialization for Mac OS X 10.5 and later.
//
// #define BACKWARD_SYSTEM_WINDOWS
//  - specialization for Windows (Clang 9 and MSVC2017)
//
// #define BACKWARD_SYSTEM_UNKNOWN
//	- placebo implementation, does nothing.
//
#if defined(BACKWARD_SYSTEM_LINUX)
#elif defined(BACKWARD_SYSTEM_DARWIN)
#elif defined(BACKWARD_SYSTEM_UNKNOWN)
#elif defined(BACKWARD_SYSTEM_WINDOWS)
#else
#if defined(__linux) || defined(__linux__)
#define BACKWARD_SYSTEM_LINUX
#elif defined(__APPLE__)
#define BACKWARD_SYSTEM_DARWIN
#elif defined(_WIN32)
#define BACKWARD_SYSTEM_WINDOWS
#else
#define BACKWARD_SYSTEM_UNKNOWN
#endif
#endif

#define NOINLINE __attribute__((noinline))

#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <new>
#include <sstream>
#include <streambuf>
#include <string>
#include <vector>
#include <exception>
#include <iterator>

#if defined(BACKWARD_SYSTEM_LINUX)

// On linux, backtrace can back-trace or "walk" the stack using the following
// libraries:
//
// #define BACKWARD_HAS_UNWIND 1
//  - unwind comes from libgcc, but I saw an equivalent inside clang itself.
//  - with unwind, the stacktrace is as accurate as it can possibly be, since
//  this is used by the C++ runtine in gcc/clang for stack unwinding on
//  exception.
//  - normally libgcc is already linked to your program by default.
//
// #define BACKWARD_HAS_LIBUNWIND 1
//  - libunwind provides, in some cases, a more accurate stacktrace as it knows
//  to decode signal handler frames and lets us edit the context registers when
//  unwinding, allowing stack traces over bad function references.
//
// #define BACKWARD_HAS_BACKTRACE == 1
//  - backtrace seems to be a little bit more portable than libunwind, but on
//  linux, it uses unwind anyway, but abstract away a tiny information that is
//  sadly really important in order to get perfectly accurate stack traces.
//  - backtrace is part of the (e)glib library.
//
// The default is:
// #define BACKWARD_HAS_UNWIND == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_UNWIND == 1
#elif BACKWARD_HAS_LIBUNWIND == 1
#elif BACKWARD_HAS_BACKTRACE == 1
#else
#undef BACKWARD_HAS_UNWIND
#define BACKWARD_HAS_UNWIND 1
#undef BACKWARD_HAS_LIBUNWIND
#define BACKWARD_HAS_LIBUNWIND 0
#undef BACKWARD_HAS_BACKTRACE
#define BACKWARD_HAS_BACKTRACE 0
#endif

// On linux, backward can extract detailed information about a stack trace
// using one of the following libraries:
//
// #define BACKWARD_HAS_DW 1
//  - libdw gives you the most juicy details out of your stack traces:
//    - object filename
//    - function name
//    - source filename
//    - line and column numbers
//    - source code snippet (assuming the file is accessible)
//    - variable names (if not optimized out)
//    - variable values (not supported by backward-cpp)
//  - You need to link with the lib "dw":
//    - apt-get install libdw-dev
//    - g++/clang++ -ldw ...
//
// #define BACKWARD_HAS_BFD 1
//  - With libbfd, you get a fair amount of details:
//    - object filename
//    - function name
//    - source filename
//    - line numbers
//    - source code snippet (assuming the file is accessible)
//  - You need to link with the lib "bfd":
//    - apt-get install binutils-dev
//    - g++/clang++ -lbfd ...
//
// #define BACKWARD_HAS_DWARF 1
//  - libdwarf gives you the most juicy details out of your stack traces:
//    - object filename
//    - function name
//    - source filename
//    - line and column numbers
//    - source code snippet (assuming the file is accessible)
//    - variable names (if not optimized out)
//    - variable values (not supported by backward-cpp)
//  - You need to link with the lib "dwarf":
//    - apt-get install libdwarf-dev
//    - g++/clang++ -ldwarf ...
//
// #define BACKWARD_HAS_BACKTRACE_SYMBOL 1
//  - backtrace provides minimal details for a stack trace:
//    - object filename
//    - function name
//  - backtrace is part of the (e)glib library.
//
// The default is:
// #define BACKWARD_HAS_BACKTRACE_SYMBOL == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_DW == 1
#elif BACKWARD_HAS_BFD == 1
#elif BACKWARD_HAS_DWARF == 1
#elif BACKWARD_HAS_BACKTRACE_SYMBOL == 1
#else
#undef BACKWARD_HAS_DW
#define BACKWARD_HAS_DW 0
#undef BACKWARD_HAS_BFD
#define BACKWARD_HAS_BFD 0
#undef BACKWARD_HAS_DWARF
#define BACKWARD_HAS_DWARF 0
#undef BACKWARD_HAS_BACKTRACE_SYMBOL
#define BACKWARD_HAS_BACKTRACE_SYMBOL 1
#endif

#include <cxxabi.h>
#include <fcntl.h>
#ifdef __ANDROID__
//		Old Android API levels define _Unwind_Ptr in both link.h and
// unwind.h 		Rename the one in link.h as we are not going to be using
// it
#define _Unwind_Ptr _Unwind_Ptr_Custom
#include <link.h>
#undef _Unwind_Ptr
#else
#include <link.h>
#endif
#include <signal.h>
#include <sys/stat.h>
#include <syscall.h>
#include <unistd.h>

#if BACKWARD_HAS_BFD == 1
//              NOTE: defining PACKAGE{,_VERSION} is required before including
//                    bfd.h on some platforms, see also:
//                    https://sourceware.org/bugzilla/show_bug.cgi?id=14243
#ifndef PACKAGE
#define PACKAGE
#endif
#ifndef PACKAGE_VERSION
#define PACKAGE_VERSION
#endif
#include <bfd.h>
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#include <dlfcn.h>
#undef _GNU_SOURCE
#else
#include <dlfcn.h>
#endif
#endif

#if BACKWARD_HAS_DW == 1
#include <dwarf.h>
#include <elfutils/libdw.h>
#include <elfutils/libdwfl.h>
#endif

#if BACKWARD_HAS_DWARF == 1
#include <algorithm>
#include <dwarf.h>
#include <libdwarf.h>
#include <libelf.h>
#include <map>
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#include <dlfcn.h>
#undef _GNU_SOURCE
#else
#include <dlfcn.h>
#endif
#endif

#if (BACKWARD_HAS_BACKTRACE == 1) || (BACKWARD_HAS_BACKTRACE_SYMBOL == 1)
// then we shall rely on backtrace
#include <execinfo.h>
#endif

#endif // defined(BACKWARD_SYSTEM_LINUX)

#if defined(BACKWARD_SYSTEM_DARWIN)
// On Darwin, backtrace can back-trace or "walk" the stack using the following
// libraries:
//
// #define BACKWARD_HAS_UNWIND 1
//  - unwind comes from libgcc, but I saw an equivalent inside clang itself.
//  - with unwind, the stacktrace is as accurate as it can possibly be, since
//  this is used by the C++ runtine in gcc/clang for stack unwinding on
//  exception.
//  - normally libgcc is already linked to your program by default.
//
// #define BACKWARD_HAS_LIBUNWIND 1
//  - libunwind comes from clang, which implements an API compatible version.
//  - libunwind provides, in some cases, a more accurate stacktrace as it knows
//  to decode signal handler frames and lets us edit the context registers when
//  unwinding, allowing stack traces over bad function references.
//
// #define BACKWARD_HAS_BACKTRACE == 1
//  - backtrace is available by default, though it does not produce as much
//  information as another library might.
//
// The default is:
// #define BACKWARD_HAS_UNWIND == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_UNWIND == 1
#elif BACKWARD_HAS_BACKTRACE == 1
#elif BACKWARD_HAS_LIBUNWIND == 1
#else
#undef BACKWARD_HAS_UNWIND
#define BACKWARD_HAS_UNWIND 1
#undef BACKWARD_HAS_BACKTRACE
#define BACKWARD_HAS_BACKTRACE 0
#undef BACKWARD_HAS_LIBUNWIND
#define BACKWARD_HAS_LIBUNWIND 0
#endif

// On Darwin, backward can extract detailed information about a stack trace
// using one of the following libraries:
//
// #define BACKWARD_HAS_BACKTRACE_SYMBOL 1
//  - backtrace provides minimal details for a stack trace:
//    - object filename
//    - function name
//
// The default is:
// #define BACKWARD_HAS_BACKTRACE_SYMBOL == 1
//
#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1
#else
#undef BACKWARD_HAS_BACKTRACE_SYMBOL
#define BACKWARD_HAS_BACKTRACE_SYMBOL 1
#endif

#include <cxxabi.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <sys/stat.h>
#include <unistd.h>

#if (BACKWARD_HAS_BACKTRACE == 1) || (BACKWARD_HAS_BACKTRACE_SYMBOL == 1)
#include <execinfo.h>
#endif
#endif // defined(BACKWARD_SYSTEM_DARWIN)

#if defined(BACKWARD_SYSTEM_WINDOWS)

#include <condition_variable>
#include <mutex>
#include <thread>

#include <basetsd.h>
typedef SSIZE_T ssize_t;

#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <windows.h>
#include <winnt.h>

#include <psapi.h>
#include <signal.h>

#ifndef __clang__
#undef NOINLINE
#define NOINLINE __declspec(noinline)
#endif

#ifdef _MSC_VER
#pragma comment(lib, "psapi.lib")
#pragma comment(lib, "dbghelp.lib")
#endif

// Comment / packing is from stackoverflow:
// https://stackoverflow.com/questions/6205981/windows-c-stack-trace-from-a-running-app/28276227#28276227
// Some versions of imagehlp.dll lack the proper packing directives themselves
// so we need to do it.
#pragma pack(push, before_imagehlp, 8)
#include <imagehlp.h>
#pragma pack(pop, before_imagehlp)

// TODO maybe these should be undefined somewhere else?
#undef BACKWARD_HAS_UNWIND
#undef BACKWARD_HAS_BACKTRACE
#if BACKWARD_HAS_PDB_SYMBOL == 1
#else
#undef BACKWARD_HAS_PDB_SYMBOL
#define BACKWARD_HAS_PDB_SYMBOL 1
#endif

#endif

#if BACKWARD_HAS_UNWIND == 1

#include <unwind.h>
// while gcc's unwind.h defines something like that:
//  extern _Unwind_Ptr _Unwind_GetIP (struct _Unwind_Context *);
//  extern _Unwind_Ptr _Unwind_GetIPInfo (struct _Unwind_Context *, int *);
//
// clang's unwind.h defines something like this:
//  uintptr_t _Unwind_GetIP(struct _Unwind_Context* __context);
//
// Even if the _Unwind_GetIPInfo can be linked to, it is not declared, worse we
// cannot just redeclare it because clang's unwind.h doesn't define _Unwind_Ptr
// anyway.
//
// Luckily we can play on the fact that the guard macros have a different name:
#ifdef __CLANG_UNWIND_H
// In fact, this function still comes from libgcc (on my different linux boxes,
// clang links against libgcc).
#include <inttypes.h>
extern "C" uintptr_t _Unwind_GetIPInfo(_Unwind_Context *, int *);
#endif

#endif // BACKWARD_HAS_UNWIND == 1

#if BACKWARD_HAS_LIBUNWIND == 1
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#endif // BACKWARD_HAS_LIBUNWIND == 1

#ifdef BACKWARD_ATLEAST_CXX11
#include <unordered_map>
#include <utility> // for std::swap
namespace backward {
   namespace details {
       template <typename K, typename V> struct hashtable {
           typedef std::unordered_map<K, V> type;
       };
       using std::move;
   } // namespace details
} // namespace backward
#else // NOT BACKWARD_ATLEAST_CXX11
#define nullptr NULL
#define override
#include <map>
namespace backward {
   namespace details {
       template <typename K, typename V> struct hashtable {
           typedef std::map<K, V> type;
       };
       template <typename T> const T &move(const T &v) { return v; }
       template <typename T> T &move(T &v) { return v; }
   } // namespace details
} // namespace backward
#endif // BACKWARD_ATLEAST_CXX11

namespace backward {
   namespace details {
#if defined(BACKWARD_SYSTEM_WINDOWS)
       const char kBackwardPathDelimiter[] = ";";
#else
       const char kBackwardPathDelimiter[] = ":";
#endif
   } // namespace details
} // namespace backward

namespace backward {

   namespace system_tag {
       struct linux_tag; // seems that I cannot call that "linux" because the name
       // is already defined... so I am adding _tag everywhere.
       struct darwin_tag;
       struct windows_tag;
       struct unknown_tag;

#if defined(BACKWARD_SYSTEM_LINUX)
       typedef linux_tag current_tag;
#elif defined(BACKWARD_SYSTEM_DARWIN)
       typedef darwin_tag current_tag;
#elif defined(BACKWARD_SYSTEM_WINDOWS)
       typedef windows_tag current_tag;
#elif defined(BACKWARD_SYSTEM_UNKNOWN)
       typedef unknown_tag current_tag;
#else
#error "May I please get my system defines?"
#endif
   } // namespace system_tag

   namespace trace_resolver_tag {
#if defined(BACKWARD_SYSTEM_LINUX)
       struct libdw;
       struct libbfd;
       struct libdwarf;
       struct backtrace_symbol;

#if BACKWARD_HAS_DW == 1
       typedef libdw current;
#elif BACKWARD_HAS_BFD == 1
       typedef libbfd current;
#elif BACKWARD_HAS_DWARF == 1
       typedef libdwarf current;
#elif BACKWARD_HAS_BACKTRACE_SYMBOL == 1
       typedef backtrace_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#elif defined(BACKWARD_SYSTEM_DARWIN)
       struct backtrace_symbol;

#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1
       typedef backtrace_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#elif defined(BACKWARD_SYSTEM_WINDOWS)
       struct pdb_symbol;
#if BACKWARD_HAS_PDB_SYMBOL == 1
       typedef pdb_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#endif
   } // namespace trace_resolver_tag

   namespace details {

       template <typename T> struct rm_ptr { typedef T type; };

       template <typename T> struct rm_ptr<T *> { typedef T type; };

       template <typename T> struct rm_ptr<const T *> { typedef const T type; };

       template <typename R, typename T, R (*F)(T)> struct deleter {
           template <typename U> void operator()(U &ptr) const { (*F)(ptr); }
       };

       template <typename T> struct default_delete {
           void operator()(T &ptr) const { delete ptr; }
       };

       template <typename T, typename Deleter = deleter<void, void *, &::free>>
       class handle {
           struct dummy;
           T _val;
           bool _empty;

#ifdef BACKWARD_ATLEAST_CXX11
           handle(const handle &) = delete;
           handle &operator=(const handle &) = delete;
#endif

       public:
           ~handle() {
               if (!_empty) {
                   Deleter()(_val);
               }
           }

           explicit handle() : _val(), _empty(true) {}
           explicit handle(T val) : _val(val), _empty(false) {
               if (!_val)
                   _empty = true;
           }

#ifdef BACKWARD_ATLEAST_CXX11
           handle(handle &&from) : _empty(true) { swap(from); }
           handle &operator=(handle &&from) {
               swap(from);
               return *this;
           }
#else
           explicit handle(const handle &from) : _empty(true) {
               // some sort of poor man's move semantic.
               swap(const_cast<handle &>(from));
           }
           handle &operator=(const handle &from) {
               // some sort of poor man's move semantic.
               swap(const_cast<handle &>(from));
               return *this;
           }
#endif

           void reset(T new_val) {
               handle tmp(new_val);
               swap(tmp);
           }

           void update(T new_val) {
               _val = new_val;
               _empty = !static_cast<bool>(new_val);
           }

           operator const dummy *() const {
               if (_empty) {
                   return nullptr;
               }
               return reinterpret_cast<const dummy *>(_val);
           }
           T get() { return _val; }
           T release() {
               _empty = true;
               return _val;
           }
           void swap(handle &b) {
               using std::swap;
               swap(b._val, _val);     // can throw, we are safe here.
               swap(b._empty, _empty); // should not throw: if you cannot swap two
                                       // bools without throwing... It's a lost cause anyway!
           }

           T &operator->() { return _val; }
           const T &operator->() const { return _val; }

           typedef typename rm_ptr<T>::type &ref_t;
           typedef const typename rm_ptr<T>::type &const_ref_t;
           ref_t operator*() { return *_val; }
           const_ref_t operator*() const { return *_val; }
           ref_t operator[](size_t idx) { return _val[idx]; }

           // Watch out, we've got a badass over here
           T *operator&() {
               _empty = false;
               return &_val;
           }
       };

       // Default demangler implementation (do nothing).
       template <typename TAG> struct demangler_impl {
           static std::string demangle(const char *funcname) { return funcname; }
       };

#if defined(BACKWARD_SYSTEM_LINUX) || defined(BACKWARD_SYSTEM_DARWIN)

       template <> struct demangler_impl<system_tag::current_tag> {
           demangler_impl() : _demangle_buffer_length(0) {}

           std::string demangle(const char *funcname) {
               using namespace details;
               char *result = abi::__cxa_demangle(funcname, _demangle_buffer.get(),
                                                  &_demangle_buffer_length, nullptr);
               if (result) {
                   _demangle_buffer.update(result);
                   return result;
               }
               return funcname;
           }

       private:
           details::handle<char *> _demangle_buffer;
           size_t _demangle_buffer_length;
       };

#endif // BACKWARD_SYSTEM_LINUX || BACKWARD_SYSTEM_DARWIN

       struct demangler : public demangler_impl<system_tag::current_tag> {};

       // Split a string on the platform's PATH delimiter.  Example: if delimiter
       // is ":" then:
       //   ""              --> []
       //   ":"             --> ["",""]
       //   "::"            --> ["","",""]
       //   "/a/b/c"        --> ["/a/b/c"]
       //   "/a/b/c:/d/e/f" --> ["/a/b/c","/d/e/f"]
       //   etc.
       inline std::vector<std::string> split_source_prefixes(const std::string &s) {
           std::vector<std::string> out;
           size_t last = 0;
           size_t next = 0;
           size_t delimiter_size = sizeof(kBackwardPathDelimiter) - 1;
           while ((next = s.find(kBackwardPathDelimiter, last)) != std::string::npos) {
               out.push_back(s.substr(last, next - last));
               last = next + delimiter_size;
           }
           if (last <= s.length()) {
               out.push_back(s.substr(last));
           }
           return out;
       }

   } // namespace details

   /*************** A TRACE ***************/

   struct Trace {
       void *addr;
       size_t idx;

       Trace() : addr(nullptr), idx(0) {}

       explicit Trace(void *_addr, size_t _idx) : addr(_addr), idx(_idx) {}
   };

   struct ResolvedTrace : public Trace {

       struct SourceLoc {
           std::string function;
           std::string filename;
           unsigned line;
           unsigned col;

           SourceLoc() : line(0), col(0) {}

           bool operator==(const SourceLoc &b) const {
               return function == b.function && filename == b.filename &&
                      line == b.line && col == b.col;
           }

           bool operator!=(const SourceLoc &b) const { return !(*this == b); }
       };

       // In which binary object this trace is located.
       std::string object_filename;

       // The function in the object that contain the trace. This is not the same
       // as source.function which can be an function inlined in object_function.
       std::string object_function;

       // The source location of this trace. It is possible for filename to be
       // empty and for line/col to be invalid (value 0) if this information
       // couldn't be deduced, for example if there is no debug information in the
       // binary object.
       SourceLoc source;

       // An optionals list of "inliners". All the successive sources location
       // from where the source location of the trace (the attribute right above)
       // is inlined. It is especially useful when you compiled with optimization.
       typedef std::vector<SourceLoc> source_locs_t;
       source_locs_t inliners;

       ResolvedTrace() : Trace() {}
       ResolvedTrace(const Trace &mini_trace) : Trace(mini_trace) {}
   };

   /*************** STACK TRACE ***************/

   // default implemention.
   template <typename TAG> class StackTraceImpl {
   public:
       size_t size() const { return 0; }
       Trace operator[](size_t) const { return Trace(); }
       size_t load_here(size_t = 0) { return 0; }
       size_t load_from(void *, size_t = 0, void * = nullptr, void * = nullptr) {
           return 0;
       }
       size_t thread_id() const { return 0; }
       void skip_n_firsts(size_t) {}
   };

   class StackTraceImplBase {
   public:
       StackTraceImplBase()
           : _thread_id(0), _skip(0), _context(nullptr), _error_addr(nullptr) {}

       size_t thread_id() const { return _thread_id; }

       void skip_n_firsts(size_t n) { _skip = n; }

   protected:
       void load_thread_info() {
#ifdef BACKWARD_SYSTEM_LINUX
#ifndef __ANDROID__
           _thread_id = static_cast<size_t>(syscall(SYS_gettid));
#else
           _thread_id = static_cast<size_t>(gettid());
#endif
           if (_thread_id == static_cast<size_t>(getpid())) {
               // If the thread is the main one, let's hide that.
               // I like to keep little secret sometimes.
               _thread_id = 0;
           }
#elif defined(BACKWARD_SYSTEM_DARWIN)
           _thread_id = reinterpret_cast<size_t>(pthread_self());
           if (pthread_main_np() == 1) {
               // If the thread is the main one, let's hide that.
               _thread_id = 0;
           }
#endif
       }

       void set_context(void *context) { _context = context; }
       void *context() const { return _context; }

       void set_error_addr(void *error_addr) { _error_addr = error_addr; }
       void *error_addr() const { return _error_addr; }

       size_t skip_n_firsts() const { return _skip; }

   private:
       size_t _thread_id;
       size_t _skip;
       void *_context;
       void *_error_addr;
   };

   class StackTraceImplHolder : public StackTraceImplBase {
   public:
       size_t size() const {
           return (_stacktrace.size() >= skip_n_firsts())
                      ? _stacktrace.size() - skip_n_firsts()
                      : 0;
       }
       Trace operator[](size_t idx) const {
           if (idx >= size()) {
               return Trace();
           }
           return Trace(_stacktrace[idx + skip_n_firsts()], idx);
       }
       void *const *begin() const {
           if (size()) {
               return &_stacktrace[skip_n_firsts()];
           }
           return nullptr;
       }

   protected:
       std::vector<void *> _stacktrace;
   };

#if BACKWARD_HAS_UNWIND == 1

   namespace details {

       template <typename F> class Unwinder {
       public:
           size_t operator()(F &f, size_t depth) {
               _f = &f;
               _index = -1;
               _depth = depth;
               _Unwind_Backtrace(&this->backtrace_trampoline, this);
               return static_cast<size_t>(_index);
           }

       private:
           F *_f;
           ssize_t _index;
           size_t _depth;

           static _Unwind_Reason_Code backtrace_trampoline(_Unwind_Context *ctx,
                                                           void *self) {
               return (static_cast<Unwinder *>(self))->backtrace(ctx);
           }

           _Unwind_Reason_Code backtrace(_Unwind_Context *ctx) {
               if (_index >= 0 && static_cast<size_t>(_index) >= _depth)
                   return _URC_END_OF_STACK;

               int ip_before_instruction = 0;
               uintptr_t ip = _Unwind_GetIPInfo(ctx, &ip_before_instruction);

               if (!ip_before_instruction) {
                   // calculating 0-1 for unsigned, looks like a possible bug to sanitiziers,
                   // so let's do it explicitly:
                   if (ip == 0) {
                       ip = std::numeric_limits<uintptr_t>::max(); // set it to 0xffff... (as
                                                                   // from casting 0-1)
                   } else {
                       ip -= 1; // else just normally decrement it (no overflow/underflow will
                                // happen)
                   }
               }

               if (_index >= 0) { // ignore first frame.
                   (*_f)(static_cast<size_t>(_index), reinterpret_cast<void *>(ip));
               }
               _index += 1;
               return _URC_NO_REASON;
           }
       };

       template <typename F> size_t unwind(F f, size_t depth) {
           Unwinder<F> unwinder;
           return unwinder(f, depth);
       }

   } // namespace details

   template <>
   class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
   public:
       NOINLINE
       size_t load_here(size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           load_thread_info();
           set_context(context);
           set_error_addr(error_addr);
           if (depth == 0) {
               return 0;
           }
           _stacktrace.resize(depth);
           size_t trace_cnt = details::unwind(callback(*this), depth);
           _stacktrace.resize(trace_cnt);
           skip_n_firsts(0);
           return size();
       }
       size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           load_here(depth + 8, context, error_addr);

           for (size_t i = 0; i < _stacktrace.size(); ++i) {
               if (_stacktrace[i] == addr) {
                   skip_n_firsts(i);
                   break;
               }
           }

           _stacktrace.resize(std::min(_stacktrace.size(), skip_n_firsts() + depth));
           return size();
       }

   private:
       struct callback {
           StackTraceImpl &self;
           callback(StackTraceImpl &_self) : self(_self) {}

           void operator()(size_t idx, void *addr) { self._stacktrace[idx] = addr; }
       };
   };

#elif BACKWARD_HAS_LIBUNWIND == 1

   template <>
   class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
   public:
       __attribute__((noinline)) size_t load_here(size_t depth = 32,
                                                  void *_context = nullptr,
                                                  void *_error_addr = nullptr) {
           set_context(_context);
           set_error_addr(_error_addr);
           load_thread_info();
           if (depth == 0) {
               return 0;
           }
           _stacktrace.resize(depth + 1);

           int result = 0;

           unw_context_t ctx;
           size_t index = 0;

           // Add the tail call. If the Instruction Pointer is the crash address it
           // means we got a bad function pointer dereference, so we "unwind" the
           // bad pointer manually by using the return address pointed to by the
           // Stack Pointer as the Instruction Pointer and letting libunwind do
           // the rest

           if (context()) {
               ucontext_t *uctx = reinterpret_cast<ucontext_t *>(context());
#ifdef REG_RIP         // x86_64
               if (uctx->uc_mcontext.gregs[REG_RIP] ==
                   reinterpret_cast<greg_t>(error_addr())) {
                   uctx->uc_mcontext.gregs[REG_RIP] =
                       *reinterpret_cast<size_t *>(uctx->uc_mcontext.gregs[REG_RSP]);
               }
               _stacktrace[index] =
                   reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_RIP]);
               ++index;
               ctx = *reinterpret_cast<unw_context_t *>(uctx);
#elif defined(REG_EIP) // x86_32
               if (uctx->uc_mcontext.gregs[REG_EIP] ==
                   reinterpret_cast<greg_t>(error_addr())) {
                   uctx->uc_mcontext.gregs[REG_EIP] =
                       *reinterpret_cast<size_t *>(uctx->uc_mcontext.gregs[REG_ESP]);
               }
               _stacktrace[index] =
                   reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_EIP]);
               ++index;
               ctx = *reinterpret_cast<unw_context_t *>(uctx);
#elif defined(__arm__)
               // libunwind uses its own context type for ARM unwinding.
               // Copy the registers from the signal handler's context so we can
               // unwind
               unw_getcontext(&ctx);
               ctx.regs[UNW_ARM_R0] = uctx->uc_mcontext.arm_r0;
               ctx.regs[UNW_ARM_R1] = uctx->uc_mcontext.arm_r1;
               ctx.regs[UNW_ARM_R2] = uctx->uc_mcontext.arm_r2;
               ctx.regs[UNW_ARM_R3] = uctx->uc_mcontext.arm_r3;
               ctx.regs[UNW_ARM_R4] = uctx->uc_mcontext.arm_r4;
               ctx.regs[UNW_ARM_R5] = uctx->uc_mcontext.arm_r5;
               ctx.regs[UNW_ARM_R6] = uctx->uc_mcontext.arm_r6;
               ctx.regs[UNW_ARM_R7] = uctx->uc_mcontext.arm_r7;
               ctx.regs[UNW_ARM_R8] = uctx->uc_mcontext.arm_r8;
               ctx.regs[UNW_ARM_R9] = uctx->uc_mcontext.arm_r9;
               ctx.regs[UNW_ARM_R10] = uctx->uc_mcontext.arm_r10;
               ctx.regs[UNW_ARM_R11] = uctx->uc_mcontext.arm_fp;
               ctx.regs[UNW_ARM_R12] = uctx->uc_mcontext.arm_ip;
               ctx.regs[UNW_ARM_R13] = uctx->uc_mcontext.arm_sp;
               ctx.regs[UNW_ARM_R14] = uctx->uc_mcontext.arm_lr;
               ctx.regs[UNW_ARM_R15] = uctx->uc_mcontext.arm_pc;

               // If we have crashed in the PC use the LR instead, as this was
               // a bad function dereference
               if (reinterpret_cast<unsigned long>(error_addr()) ==
                   uctx->uc_mcontext.arm_pc) {
                   ctx.regs[UNW_ARM_R15] =
                       uctx->uc_mcontext.arm_lr - sizeof(unsigned long);
               }
               _stacktrace[index] = reinterpret_cast<void *>(ctx.regs[UNW_ARM_R15]);
               ++index;
#elif defined(__APPLE__) && defined(__x86_64__)
               unw_getcontext(&ctx);
               // OS X's implementation of libunwind uses its own context object
               // so we need to convert the passed context to libunwind's format
               // (information about the data layout taken from unw_getcontext.s
               // in Apple's libunwind source
               ctx.data[0] = uctx->uc_mcontext->__ss.__rax;
               ctx.data[1] = uctx->uc_mcontext->__ss.__rbx;
               ctx.data[2] = uctx->uc_mcontext->__ss.__rcx;
               ctx.data[3] = uctx->uc_mcontext->__ss.__rdx;
               ctx.data[4] = uctx->uc_mcontext->__ss.__rdi;
               ctx.data[5] = uctx->uc_mcontext->__ss.__rsi;
               ctx.data[6] = uctx->uc_mcontext->__ss.__rbp;
               ctx.data[7] = uctx->uc_mcontext->__ss.__rsp;
               ctx.data[8] = uctx->uc_mcontext->__ss.__r8;
               ctx.data[9] = uctx->uc_mcontext->__ss.__r9;
               ctx.data[10] = uctx->uc_mcontext->__ss.__r10;
               ctx.data[11] = uctx->uc_mcontext->__ss.__r11;
               ctx.data[12] = uctx->uc_mcontext->__ss.__r12;
               ctx.data[13] = uctx->uc_mcontext->__ss.__r13;
               ctx.data[14] = uctx->uc_mcontext->__ss.__r14;
               ctx.data[15] = uctx->uc_mcontext->__ss.__r15;
               ctx.data[16] = uctx->uc_mcontext->__ss.__rip;

               // If the IP is the same as the crash address we have a bad function
               // dereference The caller's address is pointed to by %rsp, so we
               // dereference that value and set it to be the next frame's IP.
               if (uctx->uc_mcontext->__ss.__rip ==
                   reinterpret_cast<__uint64_t>(error_addr())) {
                   ctx.data[16] =
                       *reinterpret_cast<__uint64_t *>(uctx->uc_mcontext->__ss.__rsp);
               }
               _stacktrace[index] = reinterpret_cast<void *>(ctx.data[16]);
               ++index;
#elif defined(__APPLE__)
               unw_getcontext(&ctx)
                   // TODO: Convert the ucontext_t to libunwind's unw_context_t like
                   // we do in 64 bits
                   if (ctx.uc_mcontext->__ss.__eip ==
                       reinterpret_cast<greg_t>(error_addr())) {
                   ctx.uc_mcontext->__ss.__eip = ctx.uc_mcontext->__ss.__esp;
               }
               _stacktrace[index] =
                   reinterpret_cast<void *>(ctx.uc_mcontext->__ss.__eip);
               ++index;
#endif
           }

           unw_cursor_t cursor;
           if (context()) {
#if defined(UNW_INIT_SIGNAL_FRAME)
               result = unw_init_local2(&cursor, &ctx, UNW_INIT_SIGNAL_FRAME);
#else
               result = unw_init_local(&cursor, &ctx);
#endif
           } else {
               unw_getcontext(&ctx);
               ;
               result = unw_init_local(&cursor, &ctx);
           }

           if (result != 0)
               return 1;

           unw_word_t ip = 0;

           while (index <= depth && unw_step(&cursor) > 0) {
               result = unw_get_reg(&cursor, UNW_REG_IP, &ip);
               if (result == 0) {
                   _stacktrace[index] = reinterpret_cast<void *>(--ip);
                   ++index;
               }
           }
           --index;

           _stacktrace.resize(index + 1);
           skip_n_firsts(0);
           return size();
       }

       size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           load_here(depth + 8, context, error_addr);

           for (size_t i = 0; i < _stacktrace.size(); ++i) {
               if (_stacktrace[i] == addr) {
                   skip_n_firsts(i);
                   _stacktrace[i] = (void *)((uintptr_t)_stacktrace[i]);
                   break;
               }
           }

           _stacktrace.resize(std::min(_stacktrace.size(), skip_n_firsts() + depth));
           return size();
       }
   };

#elif defined(BACKWARD_HAS_BACKTRACE)

   template <>
   class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
   public:
       NOINLINE
       size_t load_here(size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           set_context(context);
           set_error_addr(error_addr);
           load_thread_info();
           if (depth == 0) {
               return 0;
           }
           _stacktrace.resize(depth + 1);
           size_t trace_cnt = backtrace(&_stacktrace[0], _stacktrace.size());
           _stacktrace.resize(trace_cnt);
           skip_n_firsts(1);
           return size();
       }

       size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           load_here(depth + 8, context, error_addr);

           for (size_t i = 0; i < _stacktrace.size(); ++i) {
               if (_stacktrace[i] == addr) {
                   skip_n_firsts(i);
                   _stacktrace[i] = (void *)((uintptr_t)_stacktrace[i] + 1);
                   break;
               }
           }

           _stacktrace.resize(std::min(_stacktrace.size(), skip_n_firsts() + depth));
           return size();
       }
   };

#elif defined(BACKWARD_SYSTEM_WINDOWS)

   template <>
   class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
   public:
       // We have to load the machine type from the image info
       // So we first initialize the resolver, and it tells us this info
       void set_machine_type(DWORD machine_type) { machine_type_ = machine_type; }
       void set_context(CONTEXT *ctx) { ctx_ = ctx; }
       void set_thread_handle(HANDLE handle) { thd_ = handle; }

       NOINLINE
       size_t load_here(size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           set_context(static_cast<CONTEXT*>(context));
           set_error_addr(error_addr);
           CONTEXT localCtx; // used when no context is provided

           if (depth == 0) {
               return 0;
           }

           if (!ctx_) {
               ctx_ = &localCtx;
               RtlCaptureContext(ctx_);
           }

           if (!thd_) {
               thd_ = GetCurrentThread();
           }

           HANDLE process = GetCurrentProcess();

           STACKFRAME64 s;
           memset(&s, 0, sizeof(STACKFRAME64));

           // TODO: 32 bit context capture
           s.AddrStack.Mode = AddrModeFlat;
           s.AddrFrame.Mode = AddrModeFlat;
           s.AddrPC.Mode = AddrModeFlat;
#ifdef _M_X64
           s.AddrPC.Offset = ctx_->Rip;
           s.AddrStack.Offset = ctx_->Rsp;
           s.AddrFrame.Offset = ctx_->Rbp;
#else
           s.AddrPC.Offset = ctx_->Eip;
           s.AddrStack.Offset = ctx_->Esp;
           s.AddrFrame.Offset = ctx_->Ebp;
#endif

           if (!machine_type_) {
#ifdef _M_X64
               machine_type_ = IMAGE_FILE_MACHINE_AMD64;
#else
               machine_type_ = IMAGE_FILE_MACHINE_I386;
#endif
           }

           for (;;) {
               // NOTE: this only works if PDBs are already loaded!
               SetLastError(0);
               if (!StackWalk64(machine_type_, process, thd_, &s, ctx_, NULL,
                                SymFunctionTableAccess64, SymGetModuleBase64, NULL))
                   break;

               if (s.AddrReturn.Offset == 0)
                   break;

               _stacktrace.push_back(reinterpret_cast<void *>(s.AddrPC.Offset));

               if (size() >= depth)
                   break;
           }

           return size();
       }

       size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                        void *error_addr = nullptr) {
           load_here(depth + 8, context, error_addr);

           for (size_t i = 0; i < _stacktrace.size(); ++i) {
               if (_stacktrace[i] == addr) {
                   skip_n_firsts(i);
                   break;
               }
           }

           _stacktrace.resize(std::min(_stacktrace.size(), skip_n_firsts() + depth));
           return size();
       }

   private:
       DWORD machine_type_ = 0;
       HANDLE thd_ = 0;
       CONTEXT *ctx_ = nullptr;
   };

#endif

   class StackTrace : public StackTraceImpl<system_tag::current_tag> {};

   /*************** TRACE RESOLVER ***************/

   class TraceResolverImplBase {
   public:
       virtual ~TraceResolverImplBase() {}

       virtual void load_addresses(void *const*addresses, int address_count) {
           (void)addresses;
           (void)address_count;
       }

       template <class ST> void load_stacktrace(ST &st) {
           load_addresses(st.begin(), (int)st.size());
       }

       virtual ResolvedTrace resolve(ResolvedTrace t) { return t; }

   protected:
       std::string demangle(const char *funcname) {
           return _demangler.demangle(funcname);
       }

   private:
       details::demangler _demangler;
   };

   template <typename TAG> class TraceResolverImpl;

#ifdef BACKWARD_SYSTEM_UNKNOWN

   template <> class TraceResolverImpl<system_tag::unknown_tag>
       : public TraceResolverImplBase {};

#endif

#ifdef BACKWARD_SYSTEM_LINUX

   class TraceResolverLinuxBase : public TraceResolverImplBase {
   public:
       TraceResolverLinuxBase()
           : argv0_(get_argv0()), exec_path_(read_symlink("/proc/self/exe")) {}
       std::string resolve_exec_path(Dl_info &symbol_info) const {
           // mutates symbol_info.dli_fname to be filename to open and returns filename
           // to display
           if (symbol_info.dli_fname == argv0_) {
               // dladdr returns argv[0] in dli_fname for symbols contained in
               // the main executable, which is not a valid path if the
               // executable was found by a search of the PATH environment
               // variable; In that case, we actually open /proc/self/exe, which
               // is always the actual executable (even if it was deleted/replaced!)
               // but display the path that /proc/self/exe links to.
               // However, this right away reduces probability of successful symbol
               // resolution, because libbfd may try to find *.debug files in the
               // same dir, in case symbols are stripped. As a result, it may try
               // to find a file /proc/self/<exe_name>.debug, which obviously does
               // not exist. /proc/self/exe is a last resort. First load attempt
               // should go for the original executable file path.
               symbol_info.dli_fname = "/proc/self/exe";
               return exec_path_;
           } else {
               return symbol_info.dli_fname;
           }
       }

   private:
       std::string argv0_;
       std::string exec_path_;

       static std::string get_argv0() {
           std::string argv0;
           std::ifstream ifs("/proc/self/cmdline");
           std::getline(ifs, argv0, '\0');
           return argv0;
       }

       static std::string read_symlink(std::string const &symlink_path) {
           std::string path;
           path.resize(100);

           while (true) {
               ssize_t len =
                   ::readlink(symlink_path.c_str(), &*path.begin(), path.size());
               if (len < 0) {
                   return "";
               }
               if (static_cast<size_t>(len) == path.size()) {
                   path.resize(path.size() * 2);
               } else {
                   path.resize(static_cast<std::string::size_type>(len));
                   break;
               }
           }

           return path;
       }
   };

   template <typename STACKTRACE_TAG> class TraceResolverLinuxImpl;

#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1

   template <>
   class TraceResolverLinuxImpl<trace_resolver_tag::backtrace_symbol>
       : public TraceResolverLinuxBase {
   public:
       void load_addresses(void *const*addresses, int address_count) override {
           if (address_count == 0) {
               return;
           }
           _symbols.reset(backtrace_symbols(addresses, address_count));
       }

       ResolvedTrace resolve(ResolvedTrace trace) override {
           char *filename = _symbols[trace.idx];
           char *funcname = filename;
           while (*funcname && *funcname != '(') {
               funcname += 1;
           }
           trace.object_filename.assign(filename,
                                        funcname); // ok even if funcname is the ending
                                                   // \0 (then we assign entire string)

           if (*funcname) { // if it's not end of string (e.g. from last frame ip==0)
               funcname += 1;
               char *funcname_end = funcname;
               while (*funcname_end && *funcname_end != ')' && *funcname_end != '+') {
                   funcname_end += 1;
               }
               *funcname_end = '\0';
               trace.object_function = this->demangle(funcname);
               trace.source.function = trace.object_function; // we cannot do better.
           }
           return trace;
       }

   private:
       details::handle<char **> _symbols;
   };

#endif // BACKWARD_HAS_BACKTRACE_SYMBOL == 1

#if BACKWARD_HAS_BFD == 1

   template <>
   class TraceResolverLinuxImpl<trace_resolver_tag::libbfd>
       : public TraceResolverLinuxBase {
   public:
       TraceResolverLinuxImpl() : _bfd_loaded(false) {}

       ResolvedTrace resolve(ResolvedTrace trace) override {
           Dl_info symbol_info;

           // trace.addr is a virtual address in memory pointing to some code.
           // Let's try to find from which loaded object it comes from.
           // The loaded object can be yourself btw.
           if (!dladdr(trace.addr, &symbol_info)) {
               return trace; // dat broken trace...
           }

           // Now we get in symbol_info:
           // .dli_fname:
           //		pathname of the shared object that contains the address.
           // .dli_fbase:
           //		where the object is loaded in memory.
           // .dli_sname:
           //		the name of the nearest symbol to trace.addr, we expect a
           //		function name.
           // .dli_saddr:
           //		the exact address corresponding to .dli_sname.

           if (symbol_info.dli_sname) {
               trace.object_function = demangle(symbol_info.dli_sname);
           }

           if (!symbol_info.dli_fname) {
               return trace;
           }

           trace.object_filename = resolve_exec_path(symbol_info);
           bfd_fileobject *fobj;
           // Before rushing to resolution need to ensure the executable
           // file still can be used. For that compare inode numbers of
           // what is stored by the executable's file path, and in the
           // dli_fname, which not necessarily equals to the executable.
           // It can be a shared library, or /proc/self/exe, and in the
           // latter case has drawbacks. See the exec path resolution for
           // details. In short - the dli object should be used only as
           // the last resort.
           // If inode numbers are equal, it is known dli_fname and the
           // executable file are the same. This is guaranteed by Linux,
           // because if the executable file is changed/deleted, it will
           // be done in a new inode. The old file will be preserved in
           // /proc/self/exe, and may even have inode 0. The latter can
           // happen if the inode was actually reused, and the file was
           // kept only in the main memory.
           //
           struct stat obj_stat;
           struct stat dli_stat;
           if (stat(trace.object_filename.c_str(), &obj_stat) == 0 &&
               stat(symbol_info.dli_fname, &dli_stat) == 0 &&
               obj_stat.st_ino == dli_stat.st_ino) {
               // The executable file, and the shared object containing the
               // address are the same file. Safe to use the original path.
               // this is preferable. Libbfd will search for stripped debug
               // symbols in the same directory.
               fobj = load_object_with_bfd(trace.object_filename);
           } else{
               // The original object file was *deleted*! The only hope is
               // that the debug symbols are either inside the shared
               // object file, or are in the same directory, and this is
               // not /proc/self/exe.
               fobj = nullptr;
           }
           if (fobj == nullptr || !fobj->handle) {
               fobj = load_object_with_bfd(symbol_info.dli_fname);
               if (!fobj->handle) {
                   return trace;
               }
           }

           find_sym_result *details_selected; // to be filled.

           // trace.addr is the next instruction to be executed after returning
           // from the nested stack frame. In C++ this usually relate to the next
           // statement right after the function call that leaded to a new stack
           // frame. This is not usually what you want to see when printing out a
           // stacktrace...
           find_sym_result details_call_site =
               find_symbol_details(fobj, trace.addr, symbol_info.dli_fbase);
           details_selected = &details_call_site;

#if BACKWARD_HAS_UNWIND == 0
           // ...this is why we also try to resolve the symbol that is right
           // before the return address. If we are lucky enough, we will get the
           // line of the function that was called. But if the code is optimized,
           // we might get something absolutely not related since the compiler
           // can reschedule the return address with inline functions and
           // tail-call optimisation (among other things that I don't even know
           // or cannot even dream about with my tiny limited brain).
           find_sym_result details_adjusted_call_site = find_symbol_details(
               fobj, (void *)(uintptr_t(trace.addr) - 1), symbol_info.dli_fbase);

           // In debug mode, we should always get the right thing(TM).
           if (details_call_site.found && details_adjusted_call_site.found) {
               // Ok, we assume that details_adjusted_call_site is a better estimation.
               details_selected = &details_adjusted_call_site;
               trace.addr = (void *)(uintptr_t(trace.addr) - 1);
           }

           if (details_selected == &details_call_site && details_call_site.found) {
               // we have to re-resolve the symbol in order to reset some
               // internal state in BFD... so we can call backtrace_inliners
               // thereafter...
               details_call_site =
                   find_symbol_details(fobj, trace.addr, symbol_info.dli_fbase);
           }
#endif // BACKWARD_HAS_UNWIND

           if (details_selected->found) {
               if (details_selected->filename) {
                   trace.source.filename = details_selected->filename;
               }
               trace.source.line = details_selected->line;

               if (details_selected->funcname) {
                   // this time we get the name of the function where the code is
                   // located, instead of the function were the address is
                   // located. In short, if the code was inlined, we get the
                   // function correspoding to the code. Else we already got in
                   // trace.function.
                   trace.source.function = demangle(details_selected->funcname);

                   if (!symbol_info.dli_sname) {
                       // for the case dladdr failed to find the symbol name of
                       // the function, we might as well try to put something
                       // here.
                       trace.object_function = trace.source.function;
                   }
               }

               // Maybe the source of the trace got inlined inside the function
               // (trace.source.function). Let's see if we can get all the inlined
               // calls along the way up to the initial call site.
               trace.inliners = backtrace_inliners(fobj, *details_selected);

#if 0
                       if (trace.inliners.size() == 0) {
                               // Maybe the trace was not inlined... or maybe it was and we
                               // are lacking the debug information. Let's try to make the
                               // world better and see if we can get the line number of the
                               // function (trace.source.function) now.
                               //
                               // We will get the location of where the function start (to be
                               // exact: the first instruction that really start the
                               // function), not where the name of the function is defined.
                               // This can be quite far away from the name of the function
                               // btw.
                               //
                               // If the source of the function is the same as the source of
                               // the trace, we cannot say if the trace was really inlined or
                               // not.  However, if the filename of the source is different
                               // between the function and the trace... we can declare it as
                               // an inliner.  This is not 100% accurate, but better than
                               // nothing.

                               if (symbol_info.dli_saddr) {
                                       find_sym_result details = find_symbol_details(fobj,
                                                       symbol_info.dli_saddr,
                                                       symbol_info.dli_fbase);

                                       if (details.found) {
                                               ResolvedTrace::SourceLoc diy_inliner;
                                               diy_inliner.line = details.line;
                                               if (details.filename) {
                                                       diy_inliner.filename = details.filename;
                                               }
                                               if (details.funcname) {
                                                       diy_inliner.function = demangle(details.funcname);
                                               } else {
                                                       diy_inliner.function = trace.source.function;
                                               }
                                               if (diy_inliner != trace.source) {
                                                       trace.inliners.push_back(diy_inliner);
                                               }
                                       }
                               }
                       }
#endif
           }

           return trace;
       }

   private:
       bool _bfd_loaded;

       typedef details::handle<bfd *,
                               details::deleter<bfd_boolean, bfd *, &bfd_close>>
           bfd_handle_t;

       typedef details::handle<asymbol **> bfd_symtab_t;

       struct bfd_fileobject {
           bfd_handle_t handle;
           bfd_vma base_addr;
           bfd_symtab_t symtab;
           bfd_symtab_t dynamic_symtab;
       };

       typedef details::hashtable<std::string, bfd_fileobject>::type fobj_bfd_map_t;
       fobj_bfd_map_t _fobj_bfd_map;

       bfd_fileobject *load_object_with_bfd(const std::string &filename_object) {
           using namespace details;

           if (!_bfd_loaded) {
               using namespace details;
               bfd_init();
               _bfd_loaded = true;
           }

           fobj_bfd_map_t::iterator it = _fobj_bfd_map.find(filename_object);
           if (it != _fobj_bfd_map.end()) {
               return &it->second;
           }

           // this new object is empty for now.
           bfd_fileobject *r = &_fobj_bfd_map[filename_object];

           // we do the work temporary in this one;
           bfd_handle_t bfd_handle;

           int fd = open(filename_object.c_str(), O_RDONLY);
           bfd_handle.reset(bfd_fdopenr(filename_object.c_str(), "default", fd));
           if (!bfd_handle) {
               close(fd);
               return r;
           }

           if (!bfd_check_format(bfd_handle.get(), bfd_object)) {
               return r; // not an object? You lose.
           }

           if ((bfd_get_file_flags(bfd_handle.get()) & HAS_SYMS) == 0) {
               return r; // that's what happen when you forget to compile in debug.
           }

           ssize_t symtab_storage_size = bfd_get_symtab_upper_bound(bfd_handle.get());

           ssize_t dyn_symtab_storage_size =
               bfd_get_dynamic_symtab_upper_bound(bfd_handle.get());

           if (symtab_storage_size <= 0 && dyn_symtab_storage_size <= 0) {
               return r; // weird, is the file is corrupted?
           }

           bfd_symtab_t symtab, dynamic_symtab;
           ssize_t symcount = 0, dyn_symcount = 0;

           if (symtab_storage_size > 0) {
               symtab.reset(static_cast<bfd_symbol **>(
                   malloc(static_cast<size_t>(symtab_storage_size))));
               symcount = bfd_canonicalize_symtab(bfd_handle.get(), symtab.get());
           }

           if (dyn_symtab_storage_size > 0) {
               dynamic_symtab.reset(static_cast<bfd_symbol **>(
                   malloc(static_cast<size_t>(dyn_symtab_storage_size))));
               dyn_symcount = bfd_canonicalize_dynamic_symtab(bfd_handle.get(),
                                                              dynamic_symtab.get());
           }

           if (symcount <= 0 && dyn_symcount <= 0) {
               return r; // damned, that's a stripped file that you got there!
           }

           r->handle = move(bfd_handle);
           r->symtab = move(symtab);
           r->dynamic_symtab = move(dynamic_symtab);
           return r;
       }

       struct find_sym_result {
           bool found;
           const char *filename;
           const char *funcname;
           unsigned int line;
       };

       struct find_sym_context {
           TraceResolverLinuxImpl *self;
           bfd_fileobject *fobj;
           void *addr;
           void *base_addr;
           find_sym_result result;
       };

       find_sym_result find_symbol_details(bfd_fileobject *fobj, void *addr,
                                           void *base_addr) {
           find_sym_context context;
           context.self = this;
           context.fobj = fobj;
           context.addr = addr;
           context.base_addr = base_addr;
           context.result.found = false;
           bfd_map_over_sections(fobj->handle.get(), &find_in_section_trampoline,
                                 static_cast<void *>(&context));
           return context.result;
       }

       static void find_in_section_trampoline(bfd *, asection *section, void *data) {
           find_sym_context *context = static_cast<find_sym_context *>(data);
           context->self->find_in_section(
               reinterpret_cast<bfd_vma>(context->addr),
               reinterpret_cast<bfd_vma>(context->base_addr), context->fobj, section,
               context->result);
       }

       void find_in_section(bfd_vma addr, bfd_vma base_addr, bfd_fileobject *fobj,
                            asection *section, find_sym_result &result) {
           if (result.found)
               return;

#ifdef bfd_get_section_flags
           if ((bfd_get_section_flags(fobj->handle.get(), section) & SEC_ALLOC) == 0)
#else
           if ((bfd_section_flags(section) & SEC_ALLOC) == 0)
#endif
               return; // a debug section is never loaded automatically.

#ifdef bfd_get_section_vma
           bfd_vma sec_addr = bfd_get_section_vma(fobj->handle.get(), section);
#else
           bfd_vma sec_addr = bfd_section_vma(section);
#endif
#ifdef bfd_get_section_size
           bfd_size_type size = bfd_get_section_size(section);
#else
           bfd_size_type size = bfd_section_size(section);
#endif

           // are we in the boundaries of the section?
           if (addr < sec_addr || addr >= sec_addr + size) {
               addr -= base_addr; // oups, a relocated object, lets try again...
               if (addr < sec_addr || addr >= sec_addr + size) {
                   return;
               }
           }

#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-as-null-pointer-constant"
#endif
           if (!result.found && fobj->symtab) {
               result.found = bfd_find_nearest_line(
                   fobj->handle.get(), section, fobj->symtab.get(), addr - sec_addr,
                   &result.filename, &result.funcname, &result.line);
           }

           if (!result.found && fobj->dynamic_symtab) {
               result.found = bfd_find_nearest_line(
                   fobj->handle.get(), section, fobj->dynamic_symtab.get(),
                   addr - sec_addr, &result.filename, &result.funcname, &result.line);
           }
#if defined(__clang__)
#pragma clang diagnostic pop
#endif
       }

       ResolvedTrace::source_locs_t
       backtrace_inliners(bfd_fileobject *fobj, find_sym_result previous_result) {
           // This function can be called ONLY after a SUCCESSFUL call to
           // find_symbol_details. The state is global to the bfd_handle.
           ResolvedTrace::source_locs_t results;
           while (previous_result.found) {
               find_sym_result result;
               result.found = bfd_find_inliner_info(fobj->handle.get(), &result.filename,
                                                    &result.funcname, &result.line);

               if (result
                       .found) /* and not (
                                     cstrings_eq(previous_result.filename,
                                  result.filename) and
                                  cstrings_eq(previous_result.funcname, result.funcname)
                                     and result.line == previous_result.line
                                     )) */
               {
                   ResolvedTrace::SourceLoc src_loc;
                   src_loc.line = result.line;
                   if (result.filename) {
                       src_loc.filename = result.filename;
                   }
                   if (result.funcname) {
                       src_loc.function = demangle(result.funcname);
                   }
                   results.push_back(src_loc);
               }
               previous_result = result;
           }
           return results;
       }

       bool cstrings_eq(const char *a, const char *b) {
           if (!a || !b) {
               return false;
           }
           return strcmp(a, b) == 0;
       }
   };
#endif // BACKWARD_HAS_BFD == 1

#if BACKWARD_HAS_DW == 1

   template <>
   class TraceResolverLinuxImpl<trace_resolver_tag::libdw>
       : public TraceResolverLinuxBase {
   public:
       TraceResolverLinuxImpl() : _dwfl_handle_initialized(false) {}

       ResolvedTrace resolve(ResolvedTrace trace) override {
           using namespace details;

           Dwarf_Addr trace_addr = (Dwarf_Addr)trace.addr;

           if (!_dwfl_handle_initialized) {
               // initialize dwfl...
               _dwfl_cb.reset(new Dwfl_Callbacks);
               _dwfl_cb->find_elf = &dwfl_linux_proc_find_elf;
               _dwfl_cb->find_debuginfo = &dwfl_standard_find_debuginfo;
               _dwfl_cb->debuginfo_path = 0;

               _dwfl_handle.reset(dwfl_begin(_dwfl_cb.get()));
               _dwfl_handle_initialized = true;

               if (!_dwfl_handle) {
                   return trace;
               }

               // ...from the current process.
               dwfl_report_begin(_dwfl_handle.get());
               int r = dwfl_linux_proc_report(_dwfl_handle.get(), getpid());
               dwfl_report_end(_dwfl_handle.get(), NULL, NULL);
               if (r < 0) {
                   return trace;
               }
           }

           if (!_dwfl_handle) {
               return trace;
           }

           // find the module (binary object) that contains the trace's address.
           // This is not using any debug information, but the addresses ranges of
           // all the currently loaded binary object.
           Dwfl_Module *mod = dwfl_addrmodule(_dwfl_handle.get(), trace_addr);
           if (mod) {
               // now that we found it, lets get the name of it, this will be the
               // full path to the running binary or one of the loaded library.
               const char *module_name = dwfl_module_info(mod, 0, 0, 0, 0, 0, 0, 0);
               if (module_name) {
                   trace.object_filename = module_name;
               }
               // We also look after the name of the symbol, equal or before this
               // address. This is found by walking the symtab. We should get the
               // symbol corresponding to the function (mangled) containing the
               // address. If the code corresponding to the address was inlined,
               // this is the name of the out-most inliner function.
               const char *sym_name = dwfl_module_addrname(mod, trace_addr);
               if (sym_name) {
                   trace.object_function = demangle(sym_name);
               }
           }

           // now let's get serious, and find out the source location (file and
           // line number) of the address.

           // This function will look in .debug_aranges for the address and map it
           // to the location of the compilation unit DIE in .debug_info and
           // return it.
           Dwarf_Addr mod_bias = 0;
           Dwarf_Die *cudie = dwfl_module_addrdie(mod, trace_addr, &mod_bias);

#if 1
           if (!cudie) {
               // Sadly clang does not generate the section .debug_aranges, thus
               // dwfl_module_addrdie will fail early. Clang doesn't either set
               // the lowpc/highpc/range info for every compilation unit.
               //
               // So in order to save the world:
               // for every compilation unit, we will iterate over every single
               // DIEs. Normally functions should have a lowpc/highpc/range, which
               // we will use to infer the compilation unit.

               // note that this is probably badly inefficient.
               while ((cudie = dwfl_module_nextcu(mod, cudie, &mod_bias))) {
                   Dwarf_Die die_mem;
                   Dwarf_Die *fundie =
                       find_fundie_by_pc(cudie, trace_addr - mod_bias, &die_mem);
                   if (fundie) {
                       break;
                   }
               }
           }
#endif

//#define BACKWARD_I_DO_NOT_RECOMMEND_TO_ENABLE_THIS_HORRIBLE_PIECE_OF_CODE
#ifdef BACKWARD_I_DO_NOT_RECOMMEND_TO_ENABLE_THIS_HORRIBLE_PIECE_OF_CODE
           if (!cudie) {
               // If it's still not enough, lets dive deeper in the shit, and try
               // to save the world again: for every compilation unit, we will
               // load the corresponding .debug_line section, and see if we can
               // find our address in it.

               Dwarf_Addr cfi_bias;
               Dwarf_CFI *cfi_cache = dwfl_module_eh_cfi(mod, &cfi_bias);

               Dwarf_Addr bias;
               while ((cudie = dwfl_module_nextcu(mod, cudie, &bias))) {
                   if (dwarf_getsrc_die(cudie, trace_addr - bias)) {

                       // ...but if we get a match, it might be a false positive
                       // because our (address - bias) might as well be valid in a
                       // different compilation unit. So we throw our last card on
                       // the table and lookup for the address into the .eh_frame
                       // section.

                       handle<Dwarf_Frame *> frame;
                       dwarf_cfi_addrframe(cfi_cache, trace_addr - cfi_bias, &frame);
                       if (frame) {
                           break;
                       }
                   }
               }
           }
#endif

           if (!cudie) {
               return trace; // this time we lost the game :/
           }

           // Now that we have a compilation unit DIE, this function will be able
           // to load the corresponding section in .debug_line (if not already
           // loaded) and hopefully find the source location mapped to our
           // address.
           Dwarf_Line *srcloc = dwarf_getsrc_die(cudie, trace_addr - mod_bias);

           if (srcloc) {
               const char *srcfile = dwarf_linesrc(srcloc, 0, 0);
               if (srcfile) {
                   trace.source.filename = srcfile;
               }
               int line = 0, col = 0;
               dwarf_lineno(srcloc, &line);
               dwarf_linecol(srcloc, &col);
               trace.source.line = line;
               trace.source.col = col;
           }

           deep_first_search_by_pc(cudie, trace_addr - mod_bias,
                                   inliners_search_cb(trace));
           if (trace.source.function.size() == 0) {
               // fallback.
               trace.source.function = trace.object_function;
           }

           return trace;
       }

   private:
       typedef details::handle<Dwfl *, details::deleter<void, Dwfl *, &dwfl_end>>
           dwfl_handle_t;
       details::handle<Dwfl_Callbacks *, details::default_delete<Dwfl_Callbacks *>>
           _dwfl_cb;
       dwfl_handle_t _dwfl_handle;
       bool _dwfl_handle_initialized;

       // defined here because in C++98, template function cannot take locally
       // defined types... grrr.
       struct inliners_search_cb {
           void operator()(Dwarf_Die *die) {
               switch (dwarf_tag(die)) {
                   const char *name;
                   case DW_TAG_subprogram:
                       if ((name = dwarf_diename(die))) {
                           trace.source.function = name;
                       }
                       break;

                   case DW_TAG_inlined_subroutine:
                       ResolvedTrace::SourceLoc sloc;
                       Dwarf_Attribute attr_mem;

                       if ((name = dwarf_diename(die))) {
                           sloc.function = name;
                       }
                       if ((name = die_call_file(die))) {
                           sloc.filename = name;
                       }

                       Dwarf_Word line = 0, col = 0;
                       dwarf_formudata(dwarf_attr(die, DW_AT_call_line, &attr_mem), &line);
                       dwarf_formudata(dwarf_attr(die, DW_AT_call_column, &attr_mem), &col);
                       sloc.line = (unsigned)line;
                       sloc.col = (unsigned)col;

                       trace.inliners.push_back(sloc);
                       break;
               };
           }
           ResolvedTrace &trace;
           inliners_search_cb(ResolvedTrace &t) : trace(t) {}
       };

       static bool die_has_pc(Dwarf_Die *die, Dwarf_Addr pc) {
           Dwarf_Addr low, high;

           // continuous range
           if (dwarf_hasattr(die, DW_AT_low_pc) && dwarf_hasattr(die, DW_AT_high_pc)) {
               if (dwarf_lowpc(die, &low) != 0) {
                   return false;
               }
               if (dwarf_highpc(die, &high) != 0) {
                   Dwarf_Attribute attr_mem;
                   Dwarf_Attribute *attr = dwarf_attr(die, DW_AT_high_pc, &attr_mem);
                   Dwarf_Word value;
                   if (dwarf_formudata(attr, &value) != 0) {
                       return false;
                   }
                   high = low + value;
               }
               return pc >= low && pc < high;
           }

           // non-continuous range.
           Dwarf_Addr base;
           ptrdiff_t offset = 0;
           while ((offset = dwarf_ranges(die, offset, &base, &low, &high)) > 0) {
               if (pc >= low && pc < high) {
                   return true;
               }
           }
           return false;
       }

       static Dwarf_Die *find_fundie_by_pc(Dwarf_Die *parent_die, Dwarf_Addr pc,
                                           Dwarf_Die *result) {
           if (dwarf_child(parent_die, result) != 0) {
               return 0;
           }

           Dwarf_Die *die = result;
           do {
               switch (dwarf_tag(die)) {
                   case DW_TAG_subprogram:
                   case DW_TAG_inlined_subroutine:
                       if (die_has_pc(die, pc)) {
                           return result;
                       }
               };
               bool declaration = false;
               Dwarf_Attribute attr_mem;
               dwarf_formflag(dwarf_attr(die, DW_AT_declaration, &attr_mem),
                              &declaration);
               if (!declaration) {
                   // let's be curious and look deeper in the tree,
                   // function are not necessarily at the first level, but
                   // might be nested inside a namespace, structure etc.
                   Dwarf_Die die_mem;
                   Dwarf_Die *indie = find_fundie_by_pc(die, pc, &die_mem);
                   if (indie) {
                       *result = die_mem;
                       return result;
                   }
               }
           } while (dwarf_siblingof(die, result) == 0);
           return 0;
       }

       template <typename CB>
       static bool deep_first_search_by_pc(Dwarf_Die *parent_die, Dwarf_Addr pc,
                                           CB cb) {
           Dwarf_Die die_mem;
           if (dwarf_child(parent_die, &die_mem) != 0) {
               return false;
           }

           bool branch_has_pc = false;
           Dwarf_Die *die = &die_mem;
           do {
               bool declaration = false;
               Dwarf_Attribute attr_mem;
               dwarf_formflag(dwarf_attr(die, DW_AT_declaration, &attr_mem),
                              &declaration);
               if (!declaration) {
                   // let's be curious and look deeper in the tree, function are
                   // not necessarily at the first level, but might be nested
                   // inside a namespace, structure, a function, an inlined
                   // function etc.
                   branch_has_pc = deep_first_search_by_pc(die, pc, cb);
               }
               if (!branch_has_pc) {
                   branch_has_pc = die_has_pc(die, pc);
               }
               if (branch_has_pc) {
                   cb(die);
               }
           } while (dwarf_siblingof(die, &die_mem) == 0);
           return branch_has_pc;
       }

       static const char *die_call_file(Dwarf_Die *die) {
           Dwarf_Attribute attr_mem;
           Dwarf_Word file_idx = 0;

           dwarf_formudata(dwarf_attr(die, DW_AT_call_file, &attr_mem), &file_idx);

           if (file_idx == 0) {
               return 0;
           }

           Dwarf_Die die_mem;
           Dwarf_Die *cudie = dwarf_diecu(die, &die_mem, 0, 0);
           if (!cudie) {
               return 0;
           }

           Dwarf_Files *files = 0;
           size_t nfiles;
           dwarf_getsrcfiles(cudie, &files, &nfiles);
           if (!files) {
               return 0;
           }

           return dwarf_filesrc(files, file_idx, 0, 0);
       }
   };
#endif // BACKWARD_HAS_DW == 1

#if BACKWARD_HAS_DWARF == 1

   template <>
   class TraceResolverLinuxImpl<trace_resolver_tag::libdwarf>
       : public TraceResolverLinuxBase {
   public:
       TraceResolverLinuxImpl() : _dwarf_loaded(false) {}

       ResolvedTrace resolve(ResolvedTrace trace) override {
           // trace.addr is a virtual address in memory pointing to some code.
           // Let's try to find from which loaded object it comes from.
           // The loaded object can be yourself btw.

           Dl_info symbol_info;
           int dladdr_result = 0;
#if defined(__GLIBC__)
           link_map *link_map;
           // We request the link map so we can get information about offsets
           dladdr_result =
               dladdr1(trace.addr, &symbol_info, reinterpret_cast<void **>(&link_map),
                       RTLD_DL_LINKMAP);
#else
           // Android doesn't have dladdr1. Don't use the linker map.
           dladdr_result = dladdr(trace.addr, &symbol_info);
#endif
           if (!dladdr_result) {
               return trace; // dat broken trace...
           }

           // Now we get in symbol_info:
           // .dli_fname:
           //      pathname of the shared object that contains the address.
           // .dli_fbase:
           //      where the object is loaded in memory.
           // .dli_sname:
           //      the name of the nearest symbol to trace.addr, we expect a
           //      function name.
           // .dli_saddr:
           //      the exact address corresponding to .dli_sname.
           //
           // And in link_map:
           // .l_addr:
           //      difference between the address in the ELF file and the address
           //      in memory
           // l_name:
           //      absolute pathname where the object was found

           if (symbol_info.dli_sname) {
               trace.object_function = demangle(symbol_info.dli_sname);
           }

           if (!symbol_info.dli_fname) {
               return trace;
           }

           trace.object_filename = resolve_exec_path(symbol_info);
           dwarf_fileobject &fobj = load_object_with_dwarf(symbol_info.dli_fname);
           if (!fobj.dwarf_handle) {
               return trace; // sad, we couldn't load the object :(
           }

#if defined(__GLIBC__)
           // Convert the address to a module relative one by looking at
           // the module's loading address in the link map
           Dwarf_Addr address = reinterpret_cast<uintptr_t>(trace.addr) -
                                reinterpret_cast<uintptr_t>(link_map->l_addr);
#else
           Dwarf_Addr address = reinterpret_cast<uintptr_t>(trace.addr);
#endif

           if (trace.object_function.empty()) {
               symbol_cache_t::iterator it = fobj.symbol_cache.lower_bound(address);

               if (it != fobj.symbol_cache.end()) {
                   if (it->first != address) {
                       if (it != fobj.symbol_cache.begin()) {
                           --it;
                       }
                   }
                   trace.object_function = demangle(it->second.c_str());
               }
           }

           // Get the Compilation Unit DIE for the address
           Dwarf_Die die = find_die(fobj, address);

           if (!die) {
               return trace; // this time we lost the game :/
           }

           // libdwarf doesn't give us direct access to its objects, it always
           // allocates a copy for the caller. We keep that copy alive in a cache
           // and we deallocate it later when it's no longer required.
           die_cache_entry &die_object = get_die_cache(fobj, die);
           if (die_object.isEmpty())
               return trace; // We have no line section for this DIE

           die_linemap_t::iterator it = die_object.line_section.lower_bound(address);

           if (it != die_object.line_section.end()) {
               if (it->first != address) {
                   if (it == die_object.line_section.begin()) {
                       // If we are on the first item of the line section
                       // but the address does not match it means that
                       // the address is below the range of the DIE. Give up.
                       return trace;
                   } else {
                       --it;
                   }
               }
           } else {
               return trace; // We didn't find the address.
           }

           // Get the Dwarf_Line that the address points to and call libdwarf
           // to get source file, line and column info.
           Dwarf_Line line = die_object.line_buffer[it->second];
           Dwarf_Error error = DW_DLE_NE;

           char *filename;
           if (dwarf_linesrc(line, &filename, &error) == DW_DLV_OK) {
               trace.source.filename = std::string(filename);
               dwarf_dealloc(fobj.dwarf_handle.get(), filename, DW_DLA_STRING);
           }

           Dwarf_Unsigned number = 0;
           if (dwarf_lineno(line, &number, &error) == DW_DLV_OK) {
               trace.source.line = number;
           } else {
               trace.source.line = 0;
           }

           if (dwarf_lineoff_b(line, &number, &error) == DW_DLV_OK) {
               trace.source.col = number;
           } else {
               trace.source.col = 0;
           }

           std::vector<std::string> namespace_stack;
           deep_first_search_by_pc(fobj, die, address, namespace_stack,
                                   inliners_search_cb(trace, fobj, die));

           dwarf_dealloc(fobj.dwarf_handle.get(), die, DW_DLA_DIE);

           return trace;
       }

   public:
       static int close_dwarf(Dwarf_Debug dwarf) {
           return dwarf_finish(dwarf, NULL);
       }

   private:
       bool _dwarf_loaded;

       typedef details::handle<int, details::deleter<int, int, &::close>>
           dwarf_file_t;

       typedef details::handle<Elf *, details::deleter<int, Elf *, &elf_end>>
           dwarf_elf_t;

       typedef details::handle<Dwarf_Debug,
                               details::deleter<int, Dwarf_Debug, &close_dwarf>>
           dwarf_handle_t;

       typedef std::map<Dwarf_Addr, int> die_linemap_t;

       typedef std::map<Dwarf_Off, Dwarf_Off> die_specmap_t;

       struct die_cache_entry {
           die_specmap_t spec_section;
           die_linemap_t line_section;
           Dwarf_Line *line_buffer;
           Dwarf_Signed line_count;
           Dwarf_Line_Context line_context;

           inline bool isEmpty() {
               return line_buffer == NULL || line_count == 0 || line_context == NULL ||
                      line_section.empty();
           }

           die_cache_entry() : line_buffer(0), line_count(0), line_context(0) {}

           ~die_cache_entry() {
               if (line_context) {
                   dwarf_srclines_dealloc_b(line_context);
               }
           }
       };

       typedef std::map<Dwarf_Off, die_cache_entry> die_cache_t;

       typedef std::map<uintptr_t, std::string> symbol_cache_t;

       struct dwarf_fileobject {
           dwarf_file_t file_handle;
           dwarf_elf_t elf_handle;
           dwarf_handle_t dwarf_handle;
           symbol_cache_t symbol_cache;

           // Die cache
           die_cache_t die_cache;
           die_cache_entry *current_cu;
       };

       typedef details::hashtable<std::string, dwarf_fileobject>::type
           fobj_dwarf_map_t;
       fobj_dwarf_map_t _fobj_dwarf_map;

       static bool cstrings_eq(const char *a, const char *b) {
           if (!a || !b) {
               return false;
           }
           return strcmp(a, b) == 0;
       }

       dwarf_fileobject &load_object_with_dwarf(const std::string &filename_object) {

           if (!_dwarf_loaded) {
               // Set the ELF library operating version
               // If that fails there's nothing we can do
               _dwarf_loaded = elf_version(EV_CURRENT) != EV_NONE;
           }

           fobj_dwarf_map_t::iterator it = _fobj_dwarf_map.find(filename_object);
           if (it != _fobj_dwarf_map.end()) {
               return it->second;
           }

           // this new object is empty for now
           dwarf_fileobject &r = _fobj_dwarf_map[filename_object];

           dwarf_file_t file_handle;
           file_handle.reset(open(filename_object.c_str(), O_RDONLY));
           if (file_handle.get() < 0) {
               return r;
           }

           // Try to get an ELF handle. We need to read the ELF sections
           // because we want to see if there is a .gnu_debuglink section
           // that points to a split debug file
           dwarf_elf_t elf_handle;
           elf_handle.reset(elf_begin(file_handle.get(), ELF_C_READ, NULL));
           if (!elf_handle) {
               return r;
           }

           const char *e_ident = elf_getident(elf_handle.get(), 0);
           if (!e_ident) {
               return r;
           }

           // Get the number of sections
           // We use the new APIs as elf_getshnum is deprecated
           size_t shdrnum = 0;
           if (elf_getshdrnum(elf_handle.get(), &shdrnum) == -1) {
               return r;
           }

           // Get the index to the string section
           size_t shdrstrndx = 0;
           if (elf_getshdrstrndx(elf_handle.get(), &shdrstrndx) == -1) {
               return r;
           }

           std::string debuglink;
           // Iterate through the ELF sections to try to get a gnu_debuglink
           // note and also to cache the symbol table.
           // We go the preprocessor way to avoid having to create templated
           // classes or using gelf (which might throw a compiler error if 64 bit
           // is not supported
#define ELF_GET_DATA(ARCH)                                                     \
 Elf_Scn *elf_section = 0;                                                    \
 Elf_Data *elf_data = 0;                                                      \
 Elf##ARCH##_Shdr *section_header = 0;                                        \
 Elf_Scn *symbol_section = 0;                                                 \
 size_t symbol_count = 0;                                                     \
 size_t symbol_strings = 0;                                                   \
 Elf##ARCH##_Sym *symbol = 0;                                                 \
 const char *section_name = 0;                                                \
                                                                              \
 while ((elf_section = elf_nextscn(elf_handle.get(), elf_section)) != NULL) { \
   section_header = elf##ARCH##_getshdr(elf_section);                         \
   if (section_header == NULL) {                                              \
     return r;                                                                \
   }                                                                          \
                                                                              \
   if ((section_name = elf_strptr(elf_handle.get(), shdrstrndx,               \
                                  section_header->sh_name)) == NULL) {        \
     return r;                                                                \
   }                                                                          \
                                                                              \
   if (cstrings_eq(section_name, ".gnu_debuglink")) {                         \
     elf_data = elf_getdata(elf_section, NULL);                               \
     if (elf_data && elf_data->d_size > 0) {                                  \
       debuglink =                                                            \
           std::string(reinterpret_cast<const char *>(elf_data->d_buf));      \
     }                                                                        \
   }                                                                          \
                                                                              \
   switch (section_header->sh_type) {                                         \
   case SHT_SYMTAB:                                                           \
     symbol_section = elf_section;                                            \
     symbol_count = section_header->sh_size / section_header->sh_entsize;     \
     symbol_strings = section_header->sh_link;                                \
     break;                                                                   \
                                                                              \
   /* We use .dynsyms as a last resort, we prefer .symtab */                  \
   case SHT_DYNSYM:                                                           \
     if (!symbol_section) {                                                   \
       symbol_section = elf_section;                                          \
       symbol_count = section_header->sh_size / section_header->sh_entsize;   \
       symbol_strings = section_header->sh_link;                              \
     }                                                                        \
     break;                                                                   \
   }                                                                          \
 }                                                                            \
                                                                              \
 if (symbol_section && symbol_count && symbol_strings) {                      \
   elf_data = elf_getdata(symbol_section, NULL);                              \
   symbol = reinterpret_cast<Elf##ARCH##_Sym *>(elf_data->d_buf);             \
   for (size_t i = 0; i < symbol_count; ++i) {                                \
     int type = ELF##ARCH##_ST_TYPE(symbol->st_info);                         \
     if (type == STT_FUNC && symbol->st_value > 0) {                          \
       r.symbol_cache[symbol->st_value] = std::string(                        \
           elf_strptr(elf_handle.get(), symbol_strings, symbol->st_name));    \
     }                                                                        \
     ++symbol;                                                                \
   }                                                                          \
 }

           if (e_ident[EI_CLASS] == ELFCLASS32) {
               ELF_GET_DATA(32)
           } else if (e_ident[EI_CLASS] == ELFCLASS64) {
               // libelf might have been built without 64 bit support
#if __LIBELF64
               ELF_GET_DATA(64)
#endif
           }

           if (!debuglink.empty()) {
               // We have a debuglink section! Open an elf instance on that
               // file instead. If we can't open the file, then return
               // the elf handle we had already opened.
               dwarf_file_t debuglink_file;
               debuglink_file.reset(open(debuglink.c_str(), O_RDONLY));
               if (debuglink_file.get() > 0) {
                   dwarf_elf_t debuglink_elf;
                   debuglink_elf.reset(elf_begin(debuglink_file.get(), ELF_C_READ, NULL));

                   // If we have a valid elf handle, return the new elf handle
                   // and file handle and discard the original ones
                   if (debuglink_elf) {
                       elf_handle = move(debuglink_elf);
                       file_handle = move(debuglink_file);
                   }
               }
           }

           // Ok, we have a valid ELF handle, let's try to get debug symbols
           Dwarf_Debug dwarf_debug;
           Dwarf_Error error = DW_DLE_NE;
           dwarf_handle_t dwarf_handle;

           int dwarf_result = dwarf_elf_init(elf_handle.get(), DW_DLC_READ, NULL, NULL,
                                             &dwarf_debug, &error);

           // We don't do any special handling for DW_DLV_NO_ENTRY specially.
           // If we get an error, or the file doesn't have debug information
           // we just return.
           if (dwarf_result != DW_DLV_OK) {
               return r;
           }

           dwarf_handle.reset(dwarf_debug);

           r.file_handle = move(file_handle);
           r.elf_handle = move(elf_handle);
           r.dwarf_handle = move(dwarf_handle);

           return r;
       }

       die_cache_entry &get_die_cache(dwarf_fileobject &fobj, Dwarf_Die die) {
           Dwarf_Error error = DW_DLE_NE;

           // Get the die offset, we use it as the cache key
           Dwarf_Off die_offset;
           if (dwarf_dieoffset(die, &die_offset, &error) != DW_DLV_OK) {
               die_offset = 0;
           }

           die_cache_t::iterator it = fobj.die_cache.find(die_offset);

           if (it != fobj.die_cache.end()) {
               fobj.current_cu = &it->second;
               return it->second;
           }

           die_cache_entry &de = fobj.die_cache[die_offset];
           fobj.current_cu = &de;

           Dwarf_Addr line_addr;
           Dwarf_Small table_count;

           // The addresses in the line section are not fully sorted (they might
           // be sorted by block of code belonging to the same file), which makes
           // it necessary to do so before searching is possible.
           //
           // As libdwarf allocates a copy of everything, let's get the contents
           // of the line section and keep it around. We also create a map of
           // program counter to line table indices so we can search by address
           // and get the line buffer index.
           //
           // To make things more difficult, the same address can span more than
           // one line, so we need to keep the index pointing to the first line
           // by using insert instead of the map's [ operator.

           // Get the line context for the DIE
           if (dwarf_srclines_b(die, 0, &table_count, &de.line_context, &error) ==
               DW_DLV_OK) {
               // Get the source lines for this line context, to be deallocated
               // later
               if (dwarf_srclines_from_linecontext(de.line_context, &de.line_buffer,
                                                   &de.line_count,
                                                   &error) == DW_DLV_OK) {

                   // Add all the addresses to our map
                   for (int i = 0; i < de.line_count; i++) {
                       if (dwarf_lineaddr(de.line_buffer[i], &line_addr, &error) !=
                           DW_DLV_OK) {
                           line_addr = 0;
                       }
                       de.line_section.insert(std::pair<Dwarf_Addr, int>(line_addr, i));
                   }
               }
           }

           // For each CU, cache the function DIEs that contain the
           // DW_AT_specification attribute. When building with -g3 the function
           // DIEs are separated in declaration and specification, with the
           // declaration containing only the name and parameters and the
           // specification the low/high pc and other compiler attributes.
           //
           // We cache those specifications so we don't skip over the declarations,
           // because they have no pc, and we can do namespace resolution for
           // DWARF function names.
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           Dwarf_Die current_die = 0;
           if (dwarf_child(die, &current_die, &error) == DW_DLV_OK) {
               for (;;) {
                   Dwarf_Die sibling_die = 0;

                   Dwarf_Half tag_value;
                   dwarf_tag(current_die, &tag_value, &error);

                   if (tag_value == DW_TAG_subprogram ||
                       tag_value == DW_TAG_inlined_subroutine) {

                       Dwarf_Bool has_attr = 0;
                       if (dwarf_hasattr(current_die, DW_AT_specification, &has_attr,
                                         &error) == DW_DLV_OK) {
                           if (has_attr) {
                               Dwarf_Attribute attr_mem;
                               if (dwarf_attr(current_die, DW_AT_specification, &attr_mem,
                                              &error) == DW_DLV_OK) {
                                   Dwarf_Off spec_offset = 0;
                                   if (dwarf_formref(attr_mem, &spec_offset, &error) ==
                                       DW_DLV_OK) {
                                       Dwarf_Off spec_die_offset;
                                       if (dwarf_dieoffset(current_die, &spec_die_offset, &error) ==
                                           DW_DLV_OK) {
                                           de.spec_section[spec_offset] = spec_die_offset;
                                       }
                                   }
                               }
                               dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                           }
                       }
                   }

                   int result = dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
                   if (result == DW_DLV_ERROR) {
                       break;
                   } else if (result == DW_DLV_NO_ENTRY) {
                       break;
                   }

                   if (current_die != die) {
                       dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                       current_die = 0;
                   }

                   current_die = sibling_die;
               }
           }
           return de;
       }

       static Dwarf_Die get_referenced_die(Dwarf_Debug dwarf, Dwarf_Die die,
                                           Dwarf_Half attr, bool global) {
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Attribute attr_mem;

           Dwarf_Die found_die = NULL;
           if (dwarf_attr(die, attr, &attr_mem, &error) == DW_DLV_OK) {
               Dwarf_Off offset;
               int result = 0;
               if (global) {
                   result = dwarf_global_formref(attr_mem, &offset, &error);
               } else {
                   result = dwarf_formref(attr_mem, &offset, &error);
               }

               if (result == DW_DLV_OK) {
                   if (dwarf_offdie(dwarf, offset, &found_die, &error) != DW_DLV_OK) {
                       found_die = NULL;
                   }
               }
               dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
           }
           return found_die;
       }

       static std::string get_referenced_die_name(Dwarf_Debug dwarf, Dwarf_Die die,
                                                  Dwarf_Half attr, bool global) {
           Dwarf_Error error = DW_DLE_NE;
           std::string value;

           Dwarf_Die found_die = get_referenced_die(dwarf, die, attr, global);

           if (found_die) {
               char *name;
               if (dwarf_diename(found_die, &name, &error) == DW_DLV_OK) {
                   if (name) {
                       value = std::string(name);
                   }
                   dwarf_dealloc(dwarf, name, DW_DLA_STRING);
               }
               dwarf_dealloc(dwarf, found_die, DW_DLA_DIE);
           }

           return value;
       }

       // Returns a spec DIE linked to the passed one. The caller should
       // deallocate the DIE
       static Dwarf_Die get_spec_die(dwarf_fileobject &fobj, Dwarf_Die die) {
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Off die_offset;
           if (fobj.current_cu &&
               dwarf_die_CU_offset(die, &die_offset, &error) == DW_DLV_OK) {
               die_specmap_t::iterator it =
                   fobj.current_cu->spec_section.find(die_offset);

               // If we have a DIE that completes the current one, check if
               // that one has the pc we are looking for
               if (it != fobj.current_cu->spec_section.end()) {
                   Dwarf_Die spec_die = 0;
                   if (dwarf_offdie(dwarf, it->second, &spec_die, &error) == DW_DLV_OK) {
                       return spec_die;
                   }
               }
           }

           // Maybe we have an abstract origin DIE with the function information?
           return get_referenced_die(fobj.dwarf_handle.get(), die,
                                     DW_AT_abstract_origin, true);
       }

       static bool die_has_pc(dwarf_fileobject &fobj, Dwarf_Die die, Dwarf_Addr pc) {
           Dwarf_Addr low_pc = 0, high_pc = 0;
           Dwarf_Half high_pc_form = 0;
           Dwarf_Form_Class return_class;
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           bool has_lowpc = false;
           bool has_highpc = false;
           bool has_ranges = false;

           if (dwarf_lowpc(die, &low_pc, &error) == DW_DLV_OK) {
               // If we have a low_pc check if there is a high pc.
               // If we don't have a high pc this might mean we have a base
               // address for the ranges list or just an address.
               has_lowpc = true;

               if (dwarf_highpc_b(die, &high_pc, &high_pc_form, &return_class, &error) ==
                   DW_DLV_OK) {
                   // We do have a high pc. In DWARF 4+ this is an offset from the
                   // low pc, but in earlier versions it's an absolute address.

                   has_highpc = true;
                   // In DWARF 2/3 this would be a DW_FORM_CLASS_ADDRESS
                   if (return_class == DW_FORM_CLASS_CONSTANT) {
                       high_pc = low_pc + high_pc;
                   }

                   // We have low and high pc, check if our address
                   // is in that range
                   return pc >= low_pc && pc < high_pc;
               }
           } else {
               // Reset the low_pc, in case dwarf_lowpc failing set it to some
               // undefined value.
               low_pc = 0;
           }

           // Check if DW_AT_ranges is present and search for the PC in the
           // returned ranges list. We always add the low_pc, as it not set it will
           // be 0, in case we had a DW_AT_low_pc and DW_AT_ranges pair
           bool result = false;

           Dwarf_Attribute attr;
           if (dwarf_attr(die, DW_AT_ranges, &attr, &error) == DW_DLV_OK) {

               Dwarf_Off offset;
               if (dwarf_global_formref(attr, &offset, &error) == DW_DLV_OK) {
                   Dwarf_Ranges *ranges;
                   Dwarf_Signed ranges_count = 0;
                   Dwarf_Unsigned byte_count = 0;

                   if (dwarf_get_ranges_a(dwarf, offset, die, &ranges, &ranges_count,
                                          &byte_count, &error) == DW_DLV_OK) {
                       has_ranges = ranges_count != 0;
                       for (int i = 0; i < ranges_count; i++) {
                           if (ranges[i].dwr_addr1 != 0 &&
                               pc >= ranges[i].dwr_addr1 + low_pc &&
                               pc < ranges[i].dwr_addr2 + low_pc) {
                               result = true;
                               break;
                           }
                       }
                       dwarf_ranges_dealloc(dwarf, ranges, ranges_count);
                   }
               }
           }

           // Last attempt. We might have a single address set as low_pc.
           if (!result && low_pc != 0 && pc == low_pc) {
               result = true;
           }

           // If we don't have lowpc, highpc and ranges maybe this DIE is a
           // declaration that relies on a DW_AT_specification DIE that happens
           // later. Use the specification cache we filled when we loaded this CU.
           if (!result && (!has_lowpc && !has_highpc && !has_ranges)) {
               Dwarf_Die spec_die = get_spec_die(fobj, die);
               if (spec_die) {
                   result = die_has_pc(fobj, spec_die, pc);
                   dwarf_dealloc(dwarf, spec_die, DW_DLA_DIE);
               }
           }

           return result;
       }

       static void get_type(Dwarf_Debug dwarf, Dwarf_Die die, std::string &type) {
           Dwarf_Error error = DW_DLE_NE;

           Dwarf_Die child = 0;
           if (dwarf_child(die, &child, &error) == DW_DLV_OK) {
               get_type(dwarf, child, type);
           }

           if (child) {
               type.insert(0, "::");
               dwarf_dealloc(dwarf, child, DW_DLA_DIE);
           }

           char *name;
           if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
               type.insert(0, std::string(name));
               dwarf_dealloc(dwarf, name, DW_DLA_STRING);
           } else {
               type.insert(0, "<unknown>");
           }
       }

       static std::string get_type_by_signature(Dwarf_Debug dwarf, Dwarf_Die die) {
           Dwarf_Error error = DW_DLE_NE;

           Dwarf_Sig8 signature;
           Dwarf_Bool has_attr = 0;
           if (dwarf_hasattr(die, DW_AT_signature, &has_attr, &error) == DW_DLV_OK) {
               if (has_attr) {
                   Dwarf_Attribute attr_mem;
                   if (dwarf_attr(die, DW_AT_signature, &attr_mem, &error) == DW_DLV_OK) {
                       if (dwarf_formsig8(attr_mem, &signature, &error) != DW_DLV_OK) {
                           return std::string("<no type signature>");
                       }
                   }
                   dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
               }
           }

           Dwarf_Unsigned next_cu_header;
           Dwarf_Sig8 tu_signature;
           std::string result;
           bool found = false;

           while (dwarf_next_cu_header_d(dwarf, 0, 0, 0, 0, 0, 0, 0, &tu_signature, 0,
                                         &next_cu_header, 0, &error) == DW_DLV_OK) {

               if (strncmp(signature.signature, tu_signature.signature, 8) == 0) {
                   Dwarf_Die type_cu_die = 0;
                   if (dwarf_siblingof_b(dwarf, 0, 0, &type_cu_die, &error) == DW_DLV_OK) {
                       Dwarf_Die child_die = 0;
                       if (dwarf_child(type_cu_die, &child_die, &error) == DW_DLV_OK) {
                           get_type(dwarf, child_die, result);
                           found = !result.empty();
                           dwarf_dealloc(dwarf, child_die, DW_DLA_DIE);
                       }
                       dwarf_dealloc(dwarf, type_cu_die, DW_DLA_DIE);
                   }
               }
           }

           if (found) {
               while (dwarf_next_cu_header_d(dwarf, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                                             &next_cu_header, 0, &error) == DW_DLV_OK) {
                   // Reset the cu header state. Unfortunately, libdwarf's
                   // next_cu_header API keeps its own iterator per Dwarf_Debug
                   // that can't be reset. We need to keep fetching elements until
                   // the end.
               }
           } else {
               // If we couldn't resolve the type just print out the signature
               std::ostringstream string_stream;
               string_stream << "<0x" << std::hex << std::setfill('0');
               for (int i = 0; i < 8; ++i) {
                   string_stream << std::setw(2) << std::hex
                                 << (int)(unsigned char)(signature.signature[i]);
               }
               string_stream << ">";
               result = string_stream.str();
           }
           return result;
       }

       struct type_context_t {
           bool is_const;
           bool is_typedef;
           bool has_type;
           bool has_name;
           std::string text;

           type_context_t()
               : is_const(false), is_typedef(false), has_type(false), has_name(false) {
           }
       };

       // Types are resolved from right to left: we get the variable name first
       // and then all specifiers (like const or pointer) in a chain of DW_AT_type
       // DIEs. Call this function recursively until we get a complete type
       // string.
       static void set_parameter_string(dwarf_fileobject &fobj, Dwarf_Die die,
                                        type_context_t &context) {
           char *name;
           Dwarf_Error error = DW_DLE_NE;

           // typedefs contain also the base type, so we skip it and only
           // print the typedef name
           if (!context.is_typedef) {
               if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                   if (!context.text.empty()) {
                       context.text.insert(0, " ");
                   }
                   context.text.insert(0, std::string(name));
                   dwarf_dealloc(fobj.dwarf_handle.get(), name, DW_DLA_STRING);
               }
           } else {
               context.is_typedef = false;
               context.has_type = true;
               if (context.is_const) {
                   context.text.insert(0, "const ");
                   context.is_const = false;
               }
           }

           bool next_type_is_const = false;
           bool is_keyword = true;

           Dwarf_Half tag = 0;
           Dwarf_Bool has_attr = 0;
           if (dwarf_tag(die, &tag, &error) == DW_DLV_OK) {
               switch (tag) {
                   case DW_TAG_structure_type:
                   case DW_TAG_union_type:
                   case DW_TAG_class_type:
                   case DW_TAG_enumeration_type:
                       context.has_type = true;
                       if (dwarf_hasattr(die, DW_AT_signature, &has_attr, &error) ==
                           DW_DLV_OK) {
                           // If we have a signature it means the type is defined
                           // in .debug_types, so we need to load the DIE pointed
                           // at by the signature and resolve it
                           if (has_attr) {
                               std::string type =
                                   get_type_by_signature(fobj.dwarf_handle.get(), die);
                               if (context.is_const)
                                   type.insert(0, "const ");

                               if (!context.text.empty())
                                   context.text.insert(0, " ");
                               context.text.insert(0, type);
                           }

                           // Treat enums like typedefs, and skip printing its
                           // base type
                           context.is_typedef = (tag == DW_TAG_enumeration_type);
                       }
                       break;
                   case DW_TAG_const_type:
                       next_type_is_const = true;
                       break;
                   case DW_TAG_pointer_type:
                       context.text.insert(0, "*");
                       break;
                   case DW_TAG_reference_type:
                       context.text.insert(0, "&");
                       break;
                   case DW_TAG_restrict_type:
                       context.text.insert(0, "restrict ");
                       break;
                   case DW_TAG_rvalue_reference_type:
                       context.text.insert(0, "&&");
                       break;
                   case DW_TAG_volatile_type:
                       context.text.insert(0, "volatile ");
                       break;
                   case DW_TAG_typedef:
                       // Propagate the const-ness to the next type
                       // as typedefs are linked to its base type
                       next_type_is_const = context.is_const;
                       context.is_typedef = true;
                       context.has_type = true;
                       break;
                   case DW_TAG_base_type:
                       context.has_type = true;
                       break;
                   case DW_TAG_formal_parameter:
                       context.has_name = true;
                       break;
                   default:
                       is_keyword = false;
                       break;
               }
           }

           if (!is_keyword && context.is_const) {
               context.text.insert(0, "const ");
           }

           context.is_const = next_type_is_const;

           Dwarf_Die ref =
               get_referenced_die(fobj.dwarf_handle.get(), die, DW_AT_type, true);
           if (ref) {
               set_parameter_string(fobj, ref, context);
               dwarf_dealloc(fobj.dwarf_handle.get(), ref, DW_DLA_DIE);
           }

           if (!context.has_type && context.has_name) {
               context.text.insert(0, "void ");
               context.has_type = true;
           }
       }

       // Resolve the function return type and parameters
       static void set_function_parameters(std::string &function_name,
                                           std::vector<std::string> &ns,
                                           dwarf_fileobject &fobj, Dwarf_Die die) {
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Die current_die = 0;
           std::string parameters;
           bool has_spec = true;
           // Check if we have a spec DIE. If we do we use it as it contains
           // more information, like parameter names.
           Dwarf_Die spec_die = get_spec_die(fobj, die);
           if (!spec_die) {
               has_spec = false;
               spec_die = die;
           }

           std::vector<std::string>::const_iterator it = ns.begin();
           std::string ns_name;
           for (it = ns.begin(); it < ns.end(); ++it) {
               ns_name.append(*it).append("::");
           }

           if (!ns_name.empty()) {
               function_name.insert(0, ns_name);
           }

           // See if we have a function return type. It can be either on the
           // current die or in its spec one (usually true for inlined functions)
           std::string return_type =
               get_referenced_die_name(dwarf, die, DW_AT_type, true);
           if (return_type.empty()) {
               return_type = get_referenced_die_name(dwarf, spec_die, DW_AT_type, true);
           }
           if (!return_type.empty()) {
               return_type.append(" ");
               function_name.insert(0, return_type);
           }

           if (dwarf_child(spec_die, &current_die, &error) == DW_DLV_OK) {
               for (;;) {
                   Dwarf_Die sibling_die = 0;

                   Dwarf_Half tag_value;
                   dwarf_tag(current_die, &tag_value, &error);

                   if (tag_value == DW_TAG_formal_parameter) {
                       // Ignore artificial (ie, compiler generated) parameters
                       bool is_artificial = false;
                       Dwarf_Attribute attr_mem;
                       if (dwarf_attr(current_die, DW_AT_artificial, &attr_mem, &error) ==
                           DW_DLV_OK) {
                           Dwarf_Bool flag = 0;
                           if (dwarf_formflag(attr_mem, &flag, &error) == DW_DLV_OK) {
                               is_artificial = flag != 0;
                           }
                           dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                       }

                       if (!is_artificial) {
                           type_context_t context;
                           set_parameter_string(fobj, current_die, context);

                           if (parameters.empty()) {
                               parameters.append("(");
                           } else {
                               parameters.append(", ");
                           }
                           parameters.append(context.text);
                       }
                   }

                   int result = dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
                   if (result == DW_DLV_ERROR) {
                       break;
                   } else if (result == DW_DLV_NO_ENTRY) {
                       break;
                   }

                   if (current_die != die) {
                       dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                       current_die = 0;
                   }

                   current_die = sibling_die;
               }
           }
           if (parameters.empty())
               parameters = "(";
           parameters.append(")");

           // If we got a spec DIE we need to deallocate it
           if (has_spec)
               dwarf_dealloc(dwarf, spec_die, DW_DLA_DIE);

           function_name.append(parameters);
       }

       // defined here because in C++98, template function cannot take locally
       // defined types... grrr.
       struct inliners_search_cb {
           void operator()(Dwarf_Die die, std::vector<std::string> &ns) {
               Dwarf_Error error = DW_DLE_NE;
               Dwarf_Half tag_value;
               Dwarf_Attribute attr_mem;
               Dwarf_Debug dwarf = fobj.dwarf_handle.get();

               dwarf_tag(die, &tag_value, &error);

               switch (tag_value) {
                   char *name;
                   case DW_TAG_subprogram:
                       if (!trace.source.function.empty())
                           break;
                       if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                           trace.source.function = std::string(name);
                           dwarf_dealloc(dwarf, name, DW_DLA_STRING);
                       } else {
                           // We don't have a function name in this DIE.
                           // Check if there is a referenced non-defining
                           // declaration.
                           trace.source.function =
                               get_referenced_die_name(dwarf, die, DW_AT_abstract_origin, true);
                           if (trace.source.function.empty()) {
                               trace.source.function =
                                   get_referenced_die_name(dwarf, die, DW_AT_specification, true);
                           }
                       }

                       // Append the function parameters, if available
                       set_function_parameters(trace.source.function, ns, fobj, die);

                       // If the object function name is empty, it's possible that
                       // there is no dynamic symbol table (maybe the executable
                       // was stripped or not built with -rdynamic). See if we have
                       // a DWARF linkage name to use instead. We try both
                       // linkage_name and MIPS_linkage_name because the MIPS tag
                       // was the unofficial one until it was adopted in DWARF4.
                       // Old gcc versions generate MIPS_linkage_name
                       if (trace.object_function.empty()) {
                           details::demangler demangler;

                           if (dwarf_attr(die, DW_AT_linkage_name, &attr_mem, &error) !=
                               DW_DLV_OK) {
                               if (dwarf_attr(die, DW_AT_MIPS_linkage_name, &attr_mem, &error) !=
                                   DW_DLV_OK) {
                                   break;
                               }
                           }

                           char *linkage;
                           if (dwarf_formstring(attr_mem, &linkage, &error) == DW_DLV_OK) {
                               trace.object_function = demangler.demangle(linkage);
                               dwarf_dealloc(dwarf, linkage, DW_DLA_STRING);
                           }
                           dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                       }
                       break;

                   case DW_TAG_inlined_subroutine:
                       ResolvedTrace::SourceLoc sloc;

                       if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                           sloc.function = std::string(name);
                           dwarf_dealloc(dwarf, name, DW_DLA_STRING);
                       } else {
                           // We don't have a name for this inlined DIE, it could
                           // be that there is an abstract origin instead.
                           // Get the DW_AT_abstract_origin value, which is a
                           // reference to the source DIE and try to get its name
                           sloc.function =
                               get_referenced_die_name(dwarf, die, DW_AT_abstract_origin, true);
                       }

                       set_function_parameters(sloc.function, ns, fobj, die);

                       std::string file = die_call_file(dwarf, die, cu_die);
                       if (!file.empty())
                           sloc.filename = file;

                       Dwarf_Unsigned number = 0;
                       if (dwarf_attr(die, DW_AT_call_line, &attr_mem, &error) == DW_DLV_OK) {
                           if (dwarf_formudata(attr_mem, &number, &error) == DW_DLV_OK) {
                               sloc.line = number;
                           }
                           dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                       }

                       if (dwarf_attr(die, DW_AT_call_column, &attr_mem, &error) ==
                           DW_DLV_OK) {
                           if (dwarf_formudata(attr_mem, &number, &error) == DW_DLV_OK) {
                               sloc.col = number;
                           }
                           dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                       }

                       trace.inliners.push_back(sloc);
                       break;
               };
           }
           ResolvedTrace &trace;
           dwarf_fileobject &fobj;
           Dwarf_Die cu_die;
           inliners_search_cb(ResolvedTrace &t, dwarf_fileobject &f, Dwarf_Die c)
               : trace(t), fobj(f), cu_die(c) {}
       };

       static Dwarf_Die find_fundie_by_pc(dwarf_fileobject &fobj,
                                          Dwarf_Die parent_die, Dwarf_Addr pc,
                                          Dwarf_Die result) {
           Dwarf_Die current_die = 0;
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();

           if (dwarf_child(parent_die, &current_die, &error) != DW_DLV_OK) {
               return NULL;
           }

           for (;;) {
               Dwarf_Die sibling_die = 0;
               Dwarf_Half tag_value;
               dwarf_tag(current_die, &tag_value, &error);

               switch (tag_value) {
                   case DW_TAG_subprogram:
                   case DW_TAG_inlined_subroutine:
                       if (die_has_pc(fobj, current_die, pc)) {
                           return current_die;
                       }
               };
               bool declaration = false;
               Dwarf_Attribute attr_mem;
               if (dwarf_attr(current_die, DW_AT_declaration, &attr_mem, &error) ==
                   DW_DLV_OK) {
                   Dwarf_Bool flag = 0;
                   if (dwarf_formflag(attr_mem, &flag, &error) == DW_DLV_OK) {
                       declaration = flag != 0;
                   }
                   dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
               }

               if (!declaration) {
                   // let's be curious and look deeper in the tree, functions are
                   // not necessarily at the first level, but might be nested
                   // inside a namespace, structure, a function, an inlined
                   // function etc.
                   Dwarf_Die die_mem = 0;
                   Dwarf_Die indie = find_fundie_by_pc(fobj, current_die, pc, die_mem);
                   if (indie) {
                       result = die_mem;
                       return result;
                   }
               }

               int res = dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
               if (res == DW_DLV_ERROR) {
                   return NULL;
               } else if (res == DW_DLV_NO_ENTRY) {
                   break;
               }

               if (current_die != parent_die) {
                   dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                   current_die = 0;
               }

               current_die = sibling_die;
           }
           return NULL;
       }

       template <typename CB>
       static bool deep_first_search_by_pc(dwarf_fileobject &fobj,
                                           Dwarf_Die parent_die, Dwarf_Addr pc,
                                           std::vector<std::string> &ns, CB cb) {
           Dwarf_Die current_die = 0;
           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           Dwarf_Error error = DW_DLE_NE;

           if (dwarf_child(parent_die, &current_die, &error) != DW_DLV_OK) {
               return false;
           }

           bool branch_has_pc = false;
           bool has_namespace = false;
           for (;;) {
               Dwarf_Die sibling_die = 0;

               Dwarf_Half tag;
               if (dwarf_tag(current_die, &tag, &error) == DW_DLV_OK) {
                   if (tag == DW_TAG_namespace || tag == DW_TAG_class_type) {
                       char *ns_name = NULL;
                       if (dwarf_diename(current_die, &ns_name, &error) == DW_DLV_OK) {
                           if (ns_name) {
                               ns.push_back(std::string(ns_name));
                           } else {
                               ns.push_back("<unknown>");
                           }
                           dwarf_dealloc(dwarf, ns_name, DW_DLA_STRING);
                       } else {
                           ns.push_back("<unknown>");
                       }
                       has_namespace = true;
                   }
               }

               bool declaration = false;
               Dwarf_Attribute attr_mem;
               if (tag != DW_TAG_class_type &&
                   dwarf_attr(current_die, DW_AT_declaration, &attr_mem, &error) ==
                       DW_DLV_OK) {
                   Dwarf_Bool flag = 0;
                   if (dwarf_formflag(attr_mem, &flag, &error) == DW_DLV_OK) {
                       declaration = flag != 0;
                   }
                   dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
               }

               if (!declaration) {
                   // let's be curious and look deeper in the tree, function are
                   // not necessarily at the first level, but might be nested
                   // inside a namespace, structure, a function, an inlined
                   // function etc.
                   branch_has_pc = deep_first_search_by_pc(fobj, current_die, pc, ns, cb);
               }

               if (!branch_has_pc) {
                   branch_has_pc = die_has_pc(fobj, current_die, pc);
               }

               if (branch_has_pc) {
                   cb(current_die, ns);
               }

               int result = dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
               if (result == DW_DLV_ERROR) {
                   return false;
               } else if (result == DW_DLV_NO_ENTRY) {
                   break;
               }

               if (current_die != parent_die) {
                   dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                   current_die = 0;
               }

               if (has_namespace) {
                   has_namespace = false;
                   ns.pop_back();
               }
               current_die = sibling_die;
           }

           if (has_namespace) {
               ns.pop_back();
           }
           return branch_has_pc;
       }

       static std::string die_call_file(Dwarf_Debug dwarf, Dwarf_Die die,
                                        Dwarf_Die cu_die) {
           Dwarf_Attribute attr_mem;
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Unsigned file_index;

           std::string file;

           if (dwarf_attr(die, DW_AT_call_file, &attr_mem, &error) == DW_DLV_OK) {
               if (dwarf_formudata(attr_mem, &file_index, &error) != DW_DLV_OK) {
                   file_index = 0;
               }
               dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);

               if (file_index == 0) {
                   return file;
               }

               char **srcfiles = 0;
               Dwarf_Signed file_count = 0;
               if (dwarf_srcfiles(cu_die, &srcfiles, &file_count, &error) == DW_DLV_OK) {
                   if (file_count > 0 && file_index <= static_cast<Dwarf_Unsigned>(file_count)) {
                       file = std::string(srcfiles[file_index - 1]);
                   }

                   // Deallocate all strings!
                   for (int i = 0; i < file_count; ++i) {
                       dwarf_dealloc(dwarf, srcfiles[i], DW_DLA_STRING);
                   }
                   dwarf_dealloc(dwarf, srcfiles, DW_DLA_LIST);
               }
           }
           return file;
       }

       Dwarf_Die find_die(dwarf_fileobject &fobj, Dwarf_Addr addr) {
           // Let's get to work! First see if we have a debug_aranges section so
           // we can speed up the search

           Dwarf_Debug dwarf = fobj.dwarf_handle.get();
           Dwarf_Error error = DW_DLE_NE;
           Dwarf_Arange *aranges;
           Dwarf_Signed arange_count;

           Dwarf_Die returnDie;
           bool found = false;
           if (dwarf_get_aranges(dwarf, &aranges, &arange_count, &error) !=
               DW_DLV_OK) {
               aranges = NULL;
           }

           if (aranges) {
               // We have aranges. Get the one where our address is.
               Dwarf_Arange arange;
               if (dwarf_get_arange(aranges, arange_count, addr, &arange, &error) ==
                   DW_DLV_OK) {

                   // We found our address. Get the compilation-unit DIE offset
                   // represented by the given address range.
                   Dwarf_Off cu_die_offset;
                   if (dwarf_get_cu_die_offset(arange, &cu_die_offset, &error) ==
                       DW_DLV_OK) {
                       // Get the DIE at the offset returned by the aranges search.
                       // We set is_info to 1 to specify that the offset is from
                       // the .debug_info section (and not .debug_types)
                       int dwarf_result =
                           dwarf_offdie_b(dwarf, cu_die_offset, 1, &returnDie, &error);

                       found = dwarf_result == DW_DLV_OK;
                   }
                   dwarf_dealloc(dwarf, arange, DW_DLA_ARANGE);
               }
           }

           if (found)
               return returnDie; // The caller is responsible for freeing the die

           // The search for aranges failed. Try to find our address by scanning
           // all compilation units.
           Dwarf_Unsigned next_cu_header;
           Dwarf_Half tag = 0;
           returnDie = 0;

           while (!found &&
                  dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                         &next_cu_header, 0, &error) == DW_DLV_OK) {

               if (returnDie)
                   dwarf_dealloc(dwarf, returnDie, DW_DLA_DIE);

               if (dwarf_siblingof(dwarf, 0, &returnDie, &error) == DW_DLV_OK) {
                   if ((dwarf_tag(returnDie, &tag, &error) == DW_DLV_OK) &&
                       tag == DW_TAG_compile_unit) {
                       if (die_has_pc(fobj, returnDie, addr)) {
                           found = true;
                       }
                   }
               }
           }

           if (found) {
               while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                             &next_cu_header, 0, &error) == DW_DLV_OK) {
                   // Reset the cu header state. Libdwarf's next_cu_header API
                   // keeps its own iterator per Dwarf_Debug that can't be reset.
                   // We need to keep fetching elements until the end.
               }
           }

           if (found)
               return returnDie;

           // We couldn't find any compilation units with ranges or a high/low pc.
           // Try again by looking at all DIEs in all compilation units.
           Dwarf_Die cudie;
           while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                         &next_cu_header, 0, &error) == DW_DLV_OK) {
               if (dwarf_siblingof(dwarf, 0, &cudie, &error) == DW_DLV_OK) {
                   Dwarf_Die die_mem = 0;
                   Dwarf_Die resultDie = find_fundie_by_pc(fobj, cudie, addr, die_mem);

                   if (resultDie) {
                       found = true;
                       break;
                   }
               }
           }

           if (found) {
               while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                             &next_cu_header, 0, &error) == DW_DLV_OK) {
                   // Reset the cu header state. Libdwarf's next_cu_header API
                   // keeps its own iterator per Dwarf_Debug that can't be reset.
                   // We need to keep fetching elements until the end.
               }
           }

           if (found)
               return cudie;

           // We failed.
           return NULL;
       }
   };
#endif // BACKWARD_HAS_DWARF == 1

   template <>
   class TraceResolverImpl<system_tag::linux_tag>
       : public TraceResolverLinuxImpl<trace_resolver_tag::current> {};

#endif // BACKWARD_SYSTEM_LINUX

#ifdef BACKWARD_SYSTEM_DARWIN

   template <typename STACKTRACE_TAG> class TraceResolverDarwinImpl;

   template <>
   class TraceResolverDarwinImpl<trace_resolver_tag::backtrace_symbol>
       : public TraceResolverImplBase {
   public:
       void load_addresses(void *const*addresses, int address_count) override {
           if (address_count == 0) {
               return;
           }
           _symbols.reset(backtrace_symbols(addresses, address_count));
       }

       ResolvedTrace resolve(ResolvedTrace trace) override {
           // parse:
           // <n>  <file>  <addr>  <mangled-name> + <offset>
           char *filename = _symbols[trace.idx];

           // skip "<n>  "
           while (*filename && *filename != ' ')
               filename++;
           while (*filename == ' ')
               filename++;

           // find start of <mangled-name> from end (<file> may contain a space)
           char *p = filename + strlen(filename) - 1;
           // skip to start of " + <offset>"
           while (p > filename && *p != ' ')
               p--;
           while (p > filename && *p == ' ')
               p--;
           while (p > filename && *p != ' ')
               p--;
           while (p > filename && *p == ' ')
               p--;
           char *funcname_end = p + 1;

           // skip to start of "<manged-name>"
           while (p > filename && *p != ' ')
               p--;
           char *funcname = p + 1;

           // skip to start of "  <addr>  "
           while (p > filename && *p == ' ')
               p--;
           while (p > filename && *p != ' ')
               p--;
           while (p > filename && *p == ' ')
               p--;

           // skip "<file>", handling the case where it contains a
           char *filename_end = p + 1;
           if (p == filename) {
               // something went wrong, give up
               filename_end = filename + strlen(filename);
               funcname = filename_end;
           }
           trace.object_filename.assign(
               filename, filename_end); // ok even if filename_end is the ending \0
                                        // (then we assign entire string)

           if (*funcname) { // if it's not end of string
               *funcname_end = '\0';

               trace.object_function = this->demangle(funcname);
               trace.object_function += " ";
               trace.object_function += (funcname_end + 1);
               trace.source.function = trace.object_function; // we cannot do better.
           }
           return trace;
       }

   private:
       details::handle<char **> _symbols;
   };

   template <>
   class TraceResolverImpl<system_tag::darwin_tag>
       : public TraceResolverDarwinImpl<trace_resolver_tag::current> {};

#endif // BACKWARD_SYSTEM_DARWIN

#ifdef BACKWARD_SYSTEM_WINDOWS

   // Load all symbol info
   // Based on:
   // https://stackoverflow.com/questions/6205981/windows-c-stack-trace-from-a-running-app/28276227#28276227

   struct module_data {
       std::string image_name;
       std::string module_name;
       void *base_address;
       DWORD load_size;
   };

   class get_mod_info {
       HANDLE process;
       static const int buffer_length = 4096;

   public:
       get_mod_info(HANDLE h) : process(h) {}

       module_data operator()(HMODULE module) {
           module_data ret;
           char temp[buffer_length];
           MODULEINFO mi;

           GetModuleInformation(process, module, &mi, sizeof(mi));
           ret.base_address = mi.lpBaseOfDll;
           ret.load_size = mi.SizeOfImage;

           GetModuleFileNameExA(process, module, temp, sizeof(temp));
           ret.image_name = temp;
           GetModuleBaseNameA(process, module, temp, sizeof(temp));
           ret.module_name = temp;
           std::vector<char> img(ret.image_name.begin(), ret.image_name.end());
           std::vector<char> mod(ret.module_name.begin(), ret.module_name.end());
           SymLoadModule64(process, 0, &img[0], &mod[0], (DWORD64)ret.base_address,
                           ret.load_size);
           return ret;
       }
   };

   template <> class TraceResolverImpl<system_tag::windows_tag>
       : public TraceResolverImplBase {
   public:
       TraceResolverImpl() {

           HANDLE process = GetCurrentProcess();

           std::vector<module_data> modules;
           DWORD cbNeeded;
           std::vector<HMODULE> module_handles(1);
           SymInitialize(process, NULL, false);
           DWORD symOptions = SymGetOptions();
           symOptions |= SYMOPT_LOAD_LINES | SYMOPT_UNDNAME;
           SymSetOptions(symOptions);
           EnumProcessModules(process, &module_handles[0],
                              module_handles.size() * sizeof(HMODULE), &cbNeeded);
           module_handles.resize(cbNeeded / sizeof(HMODULE));
           EnumProcessModules(process, &module_handles[0],
                              module_handles.size() * sizeof(HMODULE), &cbNeeded);
           std::transform(module_handles.begin(), module_handles.end(),
                          std::back_inserter(modules), get_mod_info(process));
           void *base = modules[0].base_address;
           IMAGE_NT_HEADERS *h = ImageNtHeader(base);
           image_type = h->FileHeader.Machine;
       }

       static const int max_sym_len = 255;
       struct symbol_t {
           SYMBOL_INFO sym;
           char buffer[max_sym_len];
       } sym;

       DWORD64 displacement;

       ResolvedTrace resolve(ResolvedTrace t) override {
           HANDLE process = GetCurrentProcess();

           char name[256];

           memset(&sym, 0, sizeof(sym));
           sym.sym.SizeOfStruct = sizeof(SYMBOL_INFO);
           sym.sym.MaxNameLen = max_sym_len;

           if (!SymFromAddr(process, (ULONG64)t.addr, &displacement, &sym.sym)) {
               // TODO:  error handling everywhere
               char* lpMsgBuf;
               DWORD dw = GetLastError();

               if (FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                                      FORMAT_MESSAGE_FROM_SYSTEM |
                                      FORMAT_MESSAGE_IGNORE_INSERTS,
                                  NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                                  (char*)&lpMsgBuf, 0, NULL)) {
                   std::fprintf(stderr, "%s\n", lpMsgBuf);
                   LocalFree(lpMsgBuf);
               }

               // abort();
           }
           UnDecorateSymbolName(sym.sym.Name, (PSTR)name, 256, UNDNAME_COMPLETE);

           DWORD offset = 0;
           IMAGEHLP_LINE line;
           if (SymGetLineFromAddr(process, (ULONG64)t.addr, &offset, &line)) {
               t.object_filename = line.FileName;
               t.source.filename = line.FileName;
               t.source.line = line.LineNumber;
               t.source.col = offset;
           }

           t.source.function = name;
           t.object_filename = "";
           t.object_function = name;

           return t;
       }

       DWORD machine_type() const { return image_type; }

   private:
       DWORD image_type;
   };

#endif

   class TraceResolver : public TraceResolverImpl<system_tag::current_tag> {};

   /*************** CODE SNIPPET ***************/

   class SourceFile {
   public:
       typedef std::vector<std::pair<unsigned, std::string>> lines_t;

       SourceFile() {}
       SourceFile(const std::string &path) {
           // 1. If BACKWARD_CXX_SOURCE_PREFIXES is set then assume it contains
           //    a colon-separated list of path prefixes.  Try prepending each
           //    to the given path until a valid file is found.
           const std::vector<std::string> &prefixes = get_paths_from_env_variable();
           for (size_t i = 0; i < prefixes.size(); ++i) {
               // Double slashes (//) should not be a problem.
               std::string new_path = prefixes[i] + '/' + path;
               _file.reset(new std::ifstream(new_path.c_str()));
               if (is_open())
                   break;
           }
           // 2. If no valid file found then fallback to opening the path as-is.
           if (!_file || !is_open()) {
               _file.reset(new std::ifstream(path.c_str()));
           }
       }
       bool is_open() const { return _file->is_open(); }

       lines_t &get_lines(unsigned line_start, unsigned line_count, lines_t &lines) {
           using namespace std;
           // This function make uses of the dumbest algo ever:
           //	1) seek(0)
           //	2) read lines one by one and discard until line_start
           //	3) read line one by one until line_start + line_count
           //
           // If you are getting snippets many time from the same file, it is
           // somewhat a waste of CPU, feel free to benchmark and propose a
           // better solution ;)

           _file->clear();
           _file->seekg(0);
           string line;
           unsigned line_idx;

           for (line_idx = 1; line_idx < line_start; ++line_idx) {
               std::getline(*_file, line);
               if (!*_file) {
                   return lines;
               }
           }

           // think of it like a lambda in C++98 ;)
           // but look, I will reuse it two times!
           // What a good boy am I.
           struct isspace {
               bool operator()(char c) { return std::isspace(c); }
           };

           bool started = false;
           for (; line_idx < line_start + line_count; ++line_idx) {
               getline(*_file, line);
               if (!*_file) {
                   return lines;
               }
               if (!started) {
                   if (std::find_if(line.begin(), line.end(), not_isspace()) == line.end())
                       continue;
                   started = true;
               }
               lines.push_back(make_pair(line_idx, line));
           }

           lines.erase(
               std::find_if(lines.rbegin(), lines.rend(), not_isempty()).base(),
               lines.end());
           return lines;
       }

       lines_t get_lines(unsigned line_start, unsigned line_count) {
           lines_t lines;
           return get_lines(line_start, line_count, lines);
       }

       // there is no find_if_not in C++98, lets do something crappy to
       // workaround.
       struct not_isspace {
           bool operator()(char c) { return !std::isspace(c); }
       };
       // and define this one here because C++98 is not happy with local defined
       // struct passed to template functions, fuuuu.
       struct not_isempty {
           bool operator()(const lines_t::value_type &p) {
               return !(std::find_if(p.second.begin(), p.second.end(), not_isspace()) ==
                        p.second.end());
           }
       };

       void swap(SourceFile &b) { _file.swap(b._file); }

#ifdef BACKWARD_ATLEAST_CXX11
       SourceFile(SourceFile &&from) : _file(nullptr) { swap(from); }
       SourceFile &operator=(SourceFile &&from) {
           swap(from);
           return *this;
       }
#else
       explicit SourceFile(const SourceFile &from) {
           // some sort of poor man's move semantic.
           swap(const_cast<SourceFile &>(from));
       }
       SourceFile &operator=(const SourceFile &from) {
           // some sort of poor man's move semantic.
           swap(const_cast<SourceFile &>(from));
           return *this;
       }
#endif

   private:
       details::handle<std::ifstream *, details::default_delete<std::ifstream *>>
           _file;

       std::vector<std::string> get_paths_from_env_variable_impl() {
           std::vector<std::string> paths;
           const char *prefixes_str = std::getenv("BACKWARD_CXX_SOURCE_PREFIXES");
           if (prefixes_str && prefixes_str[0]) {
               paths = details::split_source_prefixes(prefixes_str);
           }
           return paths;
       }

       const std::vector<std::string> &get_paths_from_env_variable() {
           static std::vector<std::string> paths = get_paths_from_env_variable_impl();
           return paths;
       }

#ifdef BACKWARD_ATLEAST_CXX11
       SourceFile(const SourceFile &) = delete;
       SourceFile &operator=(const SourceFile &) = delete;
#endif
   };

   class SnippetFactory {
   public:
       typedef SourceFile::lines_t lines_t;

       lines_t get_snippet(const std::string &filename, unsigned line_start,
                           unsigned context_size) {

           SourceFile &src_file = get_src_file(filename);
           unsigned start = line_start - context_size / 2;
           return src_file.get_lines(start, context_size);
       }

       lines_t get_combined_snippet(const std::string &filename_a, unsigned line_a,
                                    const std::string &filename_b, unsigned line_b,
                                    unsigned context_size) {
           SourceFile &src_file_a = get_src_file(filename_a);
           SourceFile &src_file_b = get_src_file(filename_b);

           lines_t lines =
               src_file_a.get_lines(line_a - context_size / 4, context_size / 2);
           src_file_b.get_lines(line_b - context_size / 4, context_size / 2, lines);
           return lines;
       }

       lines_t get_coalesced_snippet(const std::string &filename, unsigned line_a,
                                     unsigned line_b, unsigned context_size) {
           SourceFile &src_file = get_src_file(filename);

           using std::max;
           using std::min;
           unsigned a = min(line_a, line_b);
           unsigned b = max(line_a, line_b);

           if ((b - a) < (context_size / 3)) {
               return src_file.get_lines((a + b - context_size + 1) / 2, context_size);
           }

           lines_t lines = src_file.get_lines(a - context_size / 4, context_size / 2);
           src_file.get_lines(b - context_size / 4, context_size / 2, lines);
           return lines;
       }

   private:
       typedef details::hashtable<std::string, SourceFile>::type src_files_t;
       src_files_t _src_files;

       SourceFile &get_src_file(const std::string &filename) {
           src_files_t::iterator it = _src_files.find(filename);
           if (it != _src_files.end()) {
               return it->second;
           }
           SourceFile &new_src_file = _src_files[filename];
           new_src_file = SourceFile(filename);
           return new_src_file;
       }
   };

   /*************** PRINTER ***************/

   namespace ColorMode {
       enum type { automatic, never, always };
   }

   class cfile_streambuf : public std::streambuf {
   public:
       cfile_streambuf(FILE *_sink) : sink(_sink) {}
       int_type underflow() override { return traits_type::eof(); }
       int_type overflow(int_type ch) override {
           if (traits_type::not_eof(ch) && fputc(ch, sink) != EOF) {
               return ch;
           }
           return traits_type::eof();
       }

       std::streamsize xsputn(const char_type *s, std::streamsize count) override {
           return static_cast<std::streamsize>(
               fwrite(s, sizeof *s, static_cast<size_t>(count), sink));
       }

#ifdef BACKWARD_ATLEAST_CXX11
   public:
       cfile_streambuf(const cfile_streambuf &) = delete;
       cfile_streambuf &operator=(const cfile_streambuf &) = delete;
#else
   private:
       cfile_streambuf(const cfile_streambuf &);
       cfile_streambuf &operator=(const cfile_streambuf &);
#endif

   private:
       FILE *sink;
       std::vector<char> buffer;
   };

#ifdef BACKWARD_SYSTEM_LINUX

   namespace Color {
       enum type { yellow = 33, purple = 35, reset = 39 };
   } // namespace Color

   class Colorize {
   public:
       Colorize(std::ostream &os) : _os(os), _reset(false), _enabled(false) {}

       void activate(ColorMode::type mode) { _enabled = mode == ColorMode::always; }

       void activate(ColorMode::type mode, FILE *fp) { activate(mode, fileno(fp)); }

       void set_color(Color::type ccode) {
           if (!_enabled)
               return;

           // I assume that the terminal can handle basic colors. Seriously I
           // don't want to deal with all the termcap shit.
           _os << "\033[" << static_cast<int>(ccode) << "m";
           _reset = (ccode != Color::reset);
       }

       ~Colorize() {
           if (_reset) {
               set_color(Color::reset);
           }
       }

   private:
       void activate(ColorMode::type mode, int fd) {
           activate(mode == ColorMode::automatic && isatty(fd) ? ColorMode::always
                                                               : mode);
       }

       std::ostream &_os;
       bool _reset;
       bool _enabled;
   };

#else // ndef BACKWARD_SYSTEM_LINUX

   namespace Color {
       enum type { yellow = 0, purple = 0, reset = 0 };
   } // namespace Color

   class Colorize {
   public:
       Colorize(std::ostream &) {}
       void activate(ColorMode::type) {}
       void activate(ColorMode::type, FILE *) {}
       void set_color(Color::type) {}
   };

#endif // BACKWARD_SYSTEM_LINUX

   class Printer {
   public:
       bool snippet;
       ColorMode::type color_mode;
       bool address;
       bool object;
       int inliner_context_size;
       int trace_context_size;

       Printer()
           : snippet(true), color_mode(ColorMode::automatic), address(false),
             object(false), inliner_context_size(5), trace_context_size(7) {}

       template <typename ST> FILE *print(ST &st, FILE *fp = stderr) {
           cfile_streambuf obuf(fp);
           std::ostream os(&obuf);
           Colorize colorize(os);
           colorize.activate(color_mode, fp);
           print_stacktrace(st, os, colorize);
           return fp;
       }

       template <typename ST> std::ostream &print(ST &st, std::ostream &os) {
           Colorize colorize(os);
           colorize.activate(color_mode);
           print_stacktrace(st, os, colorize);
           return os;
       }

       template <typename IT>
       FILE *print(IT begin, IT end, FILE *fp = stderr, size_t thread_id = 0) {
           cfile_streambuf obuf(fp);
           std::ostream os(&obuf);
           Colorize colorize(os);
           colorize.activate(color_mode, fp);
           print_stacktrace(begin, end, os, thread_id, colorize);
           return fp;
       }

       template <typename IT>
       std::ostream &print(IT begin, IT end, std::ostream &os,
                           size_t thread_id = 0) {
           Colorize colorize(os);
           colorize.activate(color_mode);
           print_stacktrace(begin, end, os, thread_id, colorize);
           return os;
       }

       TraceResolver const &resolver() const { return _resolver; }

   private:
       TraceResolver _resolver;
       SnippetFactory _snippets;

       template <typename ST>
       void print_stacktrace(ST &st, std::ostream &os, Colorize &colorize) {
           print_header(os, st.thread_id());
           _resolver.load_stacktrace(st);
           for (size_t trace_idx = st.size(); trace_idx > 0; --trace_idx) {
               print_trace(os, _resolver.resolve(st[trace_idx - 1]), colorize);
           }
       }

       template <typename IT>
       void print_stacktrace(IT begin, IT end, std::ostream &os, size_t thread_id,
                             Colorize &colorize) {
           print_header(os, thread_id);
           for (; begin != end; ++begin) {
               print_trace(os, *begin, colorize);
           }
       }

       void print_header(std::ostream &os, size_t thread_id) {
           os << "Stack trace (most recent call last)";
           if (thread_id) {
               os << " in thread " << thread_id;
           }
           os << ":\n";
       }

       void print_trace(std::ostream &os, const ResolvedTrace &trace,
                        Colorize &colorize) {
           os << "#" << std::left << std::setw(2) << trace.idx << std::right;
           bool already_indented = true;

           if (!trace.source.filename.size() || object) {
               os << "   Object \"" << trace.object_filename << "\", at " << trace.addr
                  << ", in " << trace.object_function << "\n";
               already_indented = false;
           }

           for (size_t inliner_idx = trace.inliners.size(); inliner_idx > 0;
                --inliner_idx) {
               if (!already_indented) {
                   os << "   ";
               }
               const ResolvedTrace::SourceLoc &inliner_loc =
                   trace.inliners[inliner_idx - 1];
               print_source_loc(os, " | ", inliner_loc);
               if (snippet) {
                   print_snippet(os, "    | ", inliner_loc, colorize, Color::purple,
                                 inliner_context_size);
               }
               already_indented = false;
           }

           if (trace.source.filename.size()) {
               if (!already_indented) {
                   os << "   ";
               }
               print_source_loc(os, "   ", trace.source, trace.addr);
               if (snippet) {
                   print_snippet(os, "      ", trace.source, colorize, Color::yellow,
                                 trace_context_size);
               }
           }
       }

       void print_snippet(std::ostream &os, const char *indent,
                          const ResolvedTrace::SourceLoc &source_loc,
                          Colorize &colorize, Color::type color_code,
                          int context_size) {
           using namespace std;
           typedef SnippetFactory::lines_t lines_t;

           lines_t lines = _snippets.get_snippet(source_loc.filename, source_loc.line,
                                                 static_cast<unsigned>(context_size));

           for (lines_t::const_iterator it = lines.begin(); it != lines.end(); ++it) {
               if (it->first == source_loc.line) {
                   colorize.set_color(color_code);
                   os << indent << ">";
               } else {
                   os << indent << " ";
               }
               os << std::setw(4) << it->first << ": " << it->second << "\n";
               if (it->first == source_loc.line) {
                   colorize.set_color(Color::reset);
               }
           }
       }

       void print_source_loc(std::ostream &os, const char *indent,
                             const ResolvedTrace::SourceLoc &source_loc,
                             void *addr = nullptr) {
           os << indent << "Source \"" << source_loc.filename << "\", line "
              << source_loc.line << ", in " << source_loc.function;

           if (address && addr != nullptr) {
               os << " [" << addr << "]";
           }
           os << "\n";
       }
   };

   /*************** SIGNALS HANDLING ***************/

#if defined(BACKWARD_SYSTEM_LINUX) || defined(BACKWARD_SYSTEM_DARWIN)

   class SignalHandling {
   public:
       static std::vector<int> make_default_signals() {
           const int posix_signals[] = {
               // Signals for which the default action is "Core".
               SIGABRT, // Abort signal from abort(3)
               SIGBUS,  // Bus error (bad memory access)
               SIGFPE,  // Floating point exception
               SIGILL,  // Illegal Instruction
               SIGIOT,  // IOT trap. A synonym for SIGABRT
               SIGQUIT, // Quit from keyboard
               SIGSEGV, // Invalid memory reference
               SIGSYS,  // Bad argument to routine (SVr4)
               SIGTRAP, // Trace/breakpoint trap
               SIGXCPU, // CPU time limit exceeded (4.2BSD)
               SIGXFSZ, // File size limit exceeded (4.2BSD)
#if defined(BACKWARD_SYSTEM_DARWIN)
               SIGEMT, // emulation instruction executed
#endif
           };
           return std::vector<int>(posix_signals,
                                   posix_signals +
                                       sizeof posix_signals / sizeof posix_signals[0]);
       }

       SignalHandling(const std::vector<int> &posix_signals = make_default_signals())
           : _loaded(false) {
           bool success = true;

           const size_t stack_size = 1024 * 1024 * 8;
           _stack_content.reset(static_cast<char *>(malloc(stack_size)));
           if (_stack_content) {
               stack_t ss;
               ss.ss_sp = _stack_content.get();
               ss.ss_size = stack_size;
               ss.ss_flags = 0;
               if (sigaltstack(&ss, nullptr) < 0) {
                   success = false;
               }
           } else {
               success = false;
           }

           for (size_t i = 0; i < posix_signals.size(); ++i) {
               struct sigaction action;
               memset(&action, 0, sizeof action);
               action.sa_flags =
                   static_cast<int>(SA_SIGINFO | SA_ONSTACK | SA_NODEFER | SA_RESETHAND);
               sigfillset(&action.sa_mask);
               sigdelset(&action.sa_mask, posix_signals[i]);
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdisabled-macro-expansion"
#endif
               action.sa_sigaction = &sig_handler;
#if defined(__clang__)
#pragma clang diagnostic pop
#endif

               int r = sigaction(posix_signals[i], &action, nullptr);
               if (r < 0)
                   success = false;
           }

           _loaded = success;
       }

       bool loaded() const { return _loaded; }

       static void handleSignal(int, siginfo_t *info, void *_ctx) {
           ucontext_t *uctx = static_cast<ucontext_t *>(_ctx);

           StackTrace st;
           void *error_addr = nullptr;
#ifdef REG_RIP // x86_64
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_RIP]);
#elif defined(REG_EIP) // x86_32
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_EIP]);
#elif defined(__arm__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.arm_pc);
#elif defined(__aarch64__)
#if defined(__APPLE__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__pc);
#else
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.pc);
#endif
#elif defined(__mips__)
           error_addr = reinterpret_cast<void *>(
               reinterpret_cast<struct sigcontext *>(&uctx->uc_mcontext)->sc_pc);
#elif defined(__ppc__) || defined(__powerpc) || defined(__powerpc__) ||        \
   defined(__POWERPC__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.regs->nip);
#elif defined(__riscv)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.__gregs[REG_PC]);
#elif defined(__s390x__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.psw.addr);
#elif defined(__APPLE__) && defined(__x86_64__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__rip);
#elif defined(__APPLE__)
           error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__eip);
#else
#warning ":/ sorry, ain't know no nothing none not of your architecture!"
#endif
           if (error_addr) {
               st.load_from(error_addr, 32, reinterpret_cast<void *>(uctx),
                            info->si_addr);
           } else {
               st.load_here(32, reinterpret_cast<void *>(uctx), info->si_addr);
           }

           Printer printer;
           printer.address = true;
           printer.print(st, stderr);

#if _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           psiginfo(info, nullptr);
#else
           (void)info;
#endif
       }

   private:
       details::handle<char *> _stack_content;
       bool _loaded;

#ifdef __GNUC__
       __attribute__((noreturn))
#endif
       static void
       sig_handler(int signo, siginfo_t *info, void *_ctx) {
           handleSignal(signo, info, _ctx);

           // try to forward the signal.
           raise(info->si_signo);

           // terminate the process immediately.
           puts("watf? exit");
           _exit(EXIT_FAILURE);
       }
   };

#endif // BACKWARD_SYSTEM_LINUX || BACKWARD_SYSTEM_DARWIN

#ifdef BACKWARD_SYSTEM_WINDOWS

   class SignalHandling {
   public:
       SignalHandling(const std::vector<int> & = std::vector<int>())
           : reporter_thread_([]() {
                 /* We handle crashes in a utility thread:
                   backward structures and some Windows functions called here
                   need stack space, which we do not have when we encounter a
                   stack overflow.
                   To support reporting stack traces during a stack overflow,
                   we create a utility thread at startup, which waits until a
                   crash happens or the program exits normally. */

                 {
                     std::unique_lock<std::mutex> lk(mtx());
                     cv().wait(lk, [] { return crashed() != crash_status::running; });
                 }
                 if (crashed() == crash_status::crashed) {
                     handle_stacktrace(skip_recs());
                 }
                 {
                     std::unique_lock<std::mutex> lk(mtx());
                     crashed() = crash_status::ending;
                 }
                 cv().notify_one();
             }) {
           SetUnhandledExceptionFilter(crash_handler);

           signal(SIGABRT, signal_handler);
           _set_abort_behavior(0, _WRITE_ABORT_MSG | _CALL_REPORTFAULT);

           std::set_terminate(&terminator);
#ifndef BACKWARD_ATLEAST_CXX17
           std::set_unexpected(&terminator);
#endif
           _set_purecall_handler(&terminator);
           _set_invalid_parameter_handler(&invalid_parameter_handler);
       }
       bool loaded() const { return true; }

       ~SignalHandling() {
           {
               std::unique_lock<std::mutex> lk(mtx());
               crashed() = crash_status::normal_exit;
           }

           cv().notify_one();

           reporter_thread_.join();
       }

   private:
       static CONTEXT *ctx() {
           static CONTEXT data;
           return &data;
       }

       enum class crash_status { running, crashed, normal_exit, ending };

       static crash_status &crashed() {
           static crash_status data;
           return data;
       }

       static std::mutex &mtx() {
           static std::mutex data;
           return data;
       }

       static std::condition_variable &cv() {
           static std::condition_variable data;
           return data;
       }

       static HANDLE &thread_handle() {
           static HANDLE handle;
           return handle;
       }

       std::thread reporter_thread_;

       // TODO: how not to hardcode these?
       static const constexpr int signal_skip_recs =
#ifdef __clang__
           // With clang, RtlCaptureContext also captures the stack frame of the
           // current function Below that, there ar 3 internal Windows functions
           4
#else
           // With MSVC cl, RtlCaptureContext misses the stack frame of the current
           // function The first entries during StackWalk are the 3 internal Windows
           // functions
           3
#endif
           ;

       static int &skip_recs() {
           static int data;
           return data;
       }

       static inline void terminator() {
           crash_handler(signal_skip_recs);
           abort();
       }

       static inline void signal_handler(int) {
           crash_handler(signal_skip_recs);
           abort();
       }

       static inline void __cdecl invalid_parameter_handler(const wchar_t *,
                                                            const wchar_t *,
                                                            const wchar_t *,
                                                            unsigned int,
                                                            uintptr_t) {
           crash_handler(signal_skip_recs);
           abort();
       }

       NOINLINE static LONG WINAPI crash_handler(EXCEPTION_POINTERS *info) {
           // The exception info supplies a trace from exactly where the issue was,
           // no need to skip records
           crash_handler(0, info->ContextRecord);
           return EXCEPTION_CONTINUE_SEARCH;
       }

       NOINLINE static void crash_handler(int skip, CONTEXT *ct = nullptr) {

           if (ct == nullptr) {
               RtlCaptureContext(ctx());
           } else {
               memcpy(ctx(), ct, sizeof(CONTEXT));
           }
           DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
                           GetCurrentProcess(), &thread_handle(), 0, FALSE,
                           DUPLICATE_SAME_ACCESS);

           skip_recs() = skip;

           {
               std::unique_lock<std::mutex> lk(mtx());
               crashed() = crash_status::crashed;
           }

           cv().notify_one();

           {
               std::unique_lock<std::mutex> lk(mtx());
               cv().wait(lk, [] { return crashed() != crash_status::crashed; });
           }
       }

       static void handle_stacktrace(int skip_frames = 0) {
           // printer creates the TraceResolver, which can supply us a machine type
           // for stack walking. Without this, StackTrace can only guess using some
           // macros.
           // StackTrace also requires that the PDBs are already loaded, which is done
           // in the constructor of TraceResolver
           Printer printer;

           StackTrace st;
           st.set_machine_type(printer.resolver().machine_type());
           st.set_thread_handle(thread_handle());
           st.load_here(32 + skip_frames, ctx());
           st.skip_n_firsts(skip_frames);

           printer.address = true;
           printer.print(st, std::cerr);
       }
   };

#endif // BACKWARD_SYSTEM_WINDOWS

#ifdef BACKWARD_SYSTEM_UNKNOWN

   class SignalHandling {
   public:
       SignalHandling(const std::vector<int> & = std::vector<int>()) {}
       bool init() { return false; }
       bool loaded() { return false; }
   };

#endif // BACKWARD_SYSTEM_UNKNOWN

} // namespace backward

#endif /* H_GUARD */