Quelle backward.hpp Sprache: C

/*
* 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 <exception>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <new>
#include <sstream>
#include <streambuf>
#include <string>
#include <vector>

#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++ runtime 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
#if defined(__ppc__) || defined(__powerpc) || defined(__powerpc__) \
    || defined(__POWERPC__)
// Linux kernel header required for the struct pt_regs definition
// to access the NIP (Next Instruction Pointer) register value
#include <asm/ptrace.h>
#endif
#include <signal.h>
#include <sys/stat.h>
#include <syscall.h>
#include <unistd.h>
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#include <dlfcn.h>
#undef _GNU_SOURCE
#else
#include <dlfcn.h>
#endif

#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>
#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>
#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++ runtime 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 defined(BACKWARD_HAS_BACKTRACE_SYMBOL) && 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 defined(BACKWARD_HAS_BACKTRACE) && (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>

#ifdef _WIN64
typedef SSIZE_T ssize_t;
#else
typedef int ssize_t;
#endif

#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 defined(BACKWARD_HAS_LIBUNWIND) && 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);
        if (_index == -1) {
          // _Unwind_Backtrace has failed to obtain any backtraces
          return 0;
        } else {
          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
          // sanitizers, 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(), static_cast<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 optimization (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 corresponding 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;  // oops, 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 = reinterpret_cast<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 = static_cast<unsigned>(line);
        trace.source.col  = static_cast<unsigned>(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)) {
--> --------------------

--> maximum size reached

--> --------------------

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