backward.hpp

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/*
 * 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
#               define BACKWARD_CXX11
#               define BACKWARD_ATLEAST_CXX11
#               define BACKWARD_ATLEAST_CXX98
#       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_UNKNOWN
//      - placebo implementation, does nothing.
//
#if   defined(BACKWARD_SYSTEM_LINUX)
#elif defined(BACKWARD_SYSTEM_UNKNOWN)
#else
#       if defined(__linux)
#               define BACKWARD_SYSTEM_LINUX
#       else
#               define BACKWARD_SYSTEM_UNKNOWN
#       endif
#endif

#include <fstream>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <cctype>
#include <string>
#include <new>
#include <iomanip>
#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++ runtine in gcc/clang for stack unwinding on
//  exception.
//  - normally libgcc is already linked to your program by default.
//
// #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_BACKTRACE == 1
#       else
#               undef  BACKWARD_HAS_UNWIND
#               define BACKWARD_HAS_UNWIND 1
#               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)
//        - variables name and values (if not optimized out)
//  - 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_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_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_BACKTRACE_SYMBOL
#               define BACKWARD_HAS_BACKTRACE_SYMBOL 1
#       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

#       include <cxxabi.h>
#       include <fcntl.h>
#       include <link.h>
#       include <sys/stat.h>
#       include <syscall.h>
#       include <unistd.h>
#       include <signal.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 <elfutils/libdw.h>
#               include <elfutils/libdwfl.h>
#               include <dwarf.h>
#       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)

#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
#       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 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 unknown_tag;

#if   defined(BACKWARD_SYSTEM_LINUX)
        typedef linux_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 {
#ifdef BACKWARD_SYSTEM_LINUX
        struct libdw;
        struct libbfd;
        struct backtrace_symbol;

#       if   BACKWARD_HAS_DW == 1
        typedef libdw current;
#       elif BACKWARD_HAS_BFD == 1
        typedef libbfd current;
#       elif BACKWARD_HAS_BACKTRACE_SYMBOL == 1
        typedef backtrace_symbol current;
#       else
#               error "You shall not pass, until you know what you want."
#       endif
#endif // BACKWARD_SYSTEM_LINUX
} // 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) {}

#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);
        }
        operator const dummy*() const {
                if (_empty) {
                        return 0;
                }
                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;
        }
};

#ifdef BACKWARD_SYSTEM_LINUX

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

        std::string demangle(const char* funcname) {
                using namespace details;
                _demangle_buffer.reset(
                                abi::__cxa_demangle(funcname, _demangle_buffer.release(),
                                        &_demangle_buffer_length, 0)
                                );
                if (_demangle_buffer) {
                        return _demangle_buffer.get();
                }
                return funcname;
        }

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

#endif // BACKWARD_SYSTEM_LINUX

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

} // namespace details

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

struct Trace {
        void*    addr;
        unsigned idx;

        Trace():
                addr(0), 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) { return Trace(); }
        size_t load_here(size_t=0) { return 0; }
        size_t load_from(void*, size_t=0) { return 0; }
        unsigned thread_id() const { return 0; }
        void skip_n_firsts(size_t) { }
};

#ifdef BACKWARD_SYSTEM_LINUX

class StackTraceLinuxImplBase {
public:
        StackTraceLinuxImplBase(): _thread_id(0), _skip(0) {}

        unsigned thread_id() const {
                return _thread_id;
        }

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

protected:
        void load_thread_info() {
                _thread_id = syscall(SYS_gettid);
                if (_thread_id == (size_t) getpid()) {
                        // If the thread is the main one, let's hide that.
                        // I like to keep little secret sometimes.
                        _thread_id = 0;
                }
        }

        size_t skip_n_firsts() const { return _skip; }

private:
        size_t _thread_id;
        size_t _skip;
};

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

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 _index;
        }

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

        static _Unwind_Reason_Code backtrace_trampoline(
                        _Unwind_Context* ctx, void *self) {
                return ((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) {
                        ip -= 1;
                }

                if (_index >= 0) { // ignore first frame.
                        (*_f)(_index, (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::linux_tag>: public StackTraceLinuxImplHolder {
public:
        __attribute__ ((noinline)) // TODO use some macro
    size_t load_here(size_t depth=32) {
                load_thread_info();
                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) {
                load_here(depth + 8);

                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;
                }
        };
};


#else // BACKWARD_HAS_UNWIND == 0

template <>
class StackTraceImpl<system_tag::linux_tag>: public StackTraceLinuxImplHolder {
public:
        __attribute__ ((noinline)) // TODO use some macro
        size_t load_here(size_t depth=32) {
                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) {
                load_here(depth + 8);

                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();
        }
};

#endif // BACKWARD_HAS_UNWIND
#endif // BACKWARD_SYSTEM_LINUX

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

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

template <typename TAG>
class TraceResolverImpl;

#ifdef BACKWARD_SYSTEM_UNKNOWN

template <>
class TraceResolverImpl<system_tag::unknown_tag> {
public:
        template <class ST>
                void load_stacktrace(ST&) {}
        ResolvedTrace resolve(ResolvedTrace t) {
                return t;
        }
};

#endif

#ifdef BACKWARD_SYSTEM_LINUX

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

private:
        details::demangler _demangler;
};

template <typename STACKTRACE_TAG>
class TraceResolverLinuxImpl;

#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1

template <>
class TraceResolverLinuxImpl<trace_resolver_tag::backtrace_symbol>:
        public TraceResolverLinuxImplBase {
public:
        template <class ST>
                void load_stacktrace(ST& st) {
                        using namespace details;
                        if (st.size() == 0) {
                                return;
                        }
                        _symbols.reset(
                                        backtrace_symbols(st.begin(), st.size())
                                        );
                }

        ResolvedTrace resolve(ResolvedTrace trace) {
                char* filename = _symbols[trace.idx];
                char* funcname = filename;
                while (*funcname && *funcname != '(') {
                        funcname += 1;
                }
                trace.object_filename.assign(filename, funcname++);
                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 TraceResolverLinuxImplBase {
public:
        TraceResolverLinuxImpl(): _bfd_loaded(false) {}

        template <class ST>
                void load_stacktrace(ST&) {}

        ResolvedTrace resolve(ResolvedTrace trace) {
                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 = symbol_info.dli_fname;
                bfd_fileobject& fobj = load_object_with_bfd(symbol_info.dli_fname);
                if (!fobj.handle) {
                        return trace; // sad, we couldn't load the object :(
                }


                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(
                                        (bfd_symbol**) malloc(symtab_storage_size)
                                        );
                        symcount = bfd_canonicalize_symtab(
                                        bfd_handle.get(), symtab.get()
                                        );
                }

                if (dyn_symtab_storage_size > 0) {
                        dynamic_symtab.reset(
                                        (bfd_symbol**) malloc(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,
                                (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;

                if ((bfd_get_section_flags(fobj.handle.get(), section)
                                        & SEC_ALLOC) == 0)
                        return; // a debug section is never loaded automatically.

                bfd_vma sec_addr = bfd_get_section_vma(fobj.handle.get(), section);
                bfd_size_type size = bfd_get_section_size(section);

                // 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 (!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);
                }

        }

        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 TraceResolverLinuxImplBase {
public:
        TraceResolverLinuxImpl(): _dwfl_handle_initialized(false) {}

        template <class ST>
                void load_stacktrace(ST&) {}

        ResolvedTrace resolve(ResolvedTrace trace) {
                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 = line;
                                        sloc.col = 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;
                                        }
                                default:
                                        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_Sword file_idx = 0;

                dwarf_formsdata(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

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

#endif // BACKWARD_SYSTEM_LINUX

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): _file(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(0) {
                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;

#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::min; using std::max;
                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 ***************/

#ifdef BACKWARD_SYSTEM_LINUX

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

class Colorize {
public:
        Colorize(std::FILE* os):
                _os(os), _reset(false), _istty(false) {}

        void init() {
                _istty = isatty(fileno(_os));
        }

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

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

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

private:
        std::FILE* _os;
        bool       _reset;
        bool       _istty;
};

#else // ndef BACKWARD_SYSTEM_LINUX


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

class Colorize {
public:
        Colorize(std::FILE*) {}
        void init() {}
        void set_color(Color::type) {}
};

#endif // BACKWARD_SYSTEM_LINUX

class Printer {
public:
        bool snippet;
        bool color;
        bool address;
        bool object;
        int inliner_context_size;
        int trace_context_size;

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

        template <typename ST>
                FILE* print(ST& st, FILE* os = stderr) {
                        Colorize colorize(os);
                        if (color) {
                                colorize.init();
                        }
                        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);
                        }
                        return os;
                }

        template <typename IT>
                FILE* print(IT begin, IT end, FILE* os = stderr, size_t thread_id = 0) {
                        Colorize colorize(os);
                        if (color) {
                                colorize.init();
                        }
                        print_header(os, thread_id);
                        for (; begin != end; ++begin) {
                                print_trace(os, *begin, colorize);
                        }
                        return os;
                }
private:
        TraceResolver  _resolver;
        SnippetFactory _snippets;

        void print_header(FILE* os, unsigned thread_id) {
                fprintf(os, "Stack trace (most recent call last)");
                if (thread_id) {
                        fprintf(os, " in thread %u:\n", thread_id);
                } else {
                        fprintf(os, ":\n");
                }
        }

        void print_trace(FILE* os, const ResolvedTrace& trace,
                        Colorize& colorize) {
                fprintf(os, "#%-2u", trace.idx);
                bool already_indented = true;

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

                for (size_t inliner_idx = trace.inliners.size();
                                inliner_idx > 0; --inliner_idx) {
                        if (!already_indented) {
                                fprintf(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) {
                                fprintf(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(FILE* 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, 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);
                                fprintf(os, "%s>", indent);
                        } else {
                                fprintf(os, "%s ", indent);
                        }
                        fprintf(os, "%4u: %s\n", it->first, it->second.c_str());
                        if (it-> first == source_loc.line) {
                                colorize.set_color(Color::reset);
                        }
                }
        }

        void print_source_loc(FILE* os, const char* indent,
                        const ResolvedTrace::SourceLoc& source_loc,
                        void* addr=0) {
                fprintf(os, "%sSource \"%s\", line %i, in %s",
                                indent, source_loc.filename.c_str(), (int)source_loc.line,
                                source_loc.function.c_str());

                if (address && addr != 0) {
                        fprintf(os, " [%p]\n", addr);
                } else {
                        fprintf(os, "\n");
                }
        }
};

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

#ifdef BACKWARD_SYSTEM_LINUX


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)
        };
        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((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, 0) < 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 = (SA_SIGINFO | SA_ONSTACK | SA_NODEFER |
                                        SA_RESETHAND);
                        sigfillset(&action.sa_mask);
                        sigdelset(&action.sa_mask, posix_signals[i]);
                        action.sa_sigaction = &sig_handler;

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

                _loaded = success;
        }

        bool loaded() const { return _loaded; }

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

#ifdef __GNUC__
        __attribute__((noreturn))
#endif
        static void sig_handler(int, siginfo_t* info, void* _ctx) {
                ucontext_t *uctx = (ucontext_t*) _ctx;

                StackTrace st;
                void* error_addr = 0;
#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(__ppc__) || defined(__powerpc) || defined(__powerpc__) || defined(__POWERPC__)
                error_addr = reinterpret_cast<void*>(uctx->uc_mcontext.regs->nip);
#else
#       warning ":/ sorry, ain't know no nothing none not of your architecture!"
#endif
                if (error_addr) {
            st.load_from(error_addr, 32);
                } else {
            st.load_here(32);
                }

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

#if _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
                psiginfo(info, 0);
#endif

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

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

#endif // BACKWARD_SYSTEM_LINUX

#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 */