how to print function backtrack with boost

How to print current call
stack

boost::stacktrace::stacktrace

contains methods for working with call-stack/backtraces/stacktraces.
Here's a small example:

#include <boost/stacktrace.hpp>

// ... somewhere inside the `bar(int)` function that is called recursively:
std::cout << boost::stacktrace::stacktrace();

In that example:

boost::stacktrace::

is the namespace that has all the classes and functions to
work with stacktraces

stacktrace()

is the default constructor call; constructor
stores the current function call sequence inside the stacktrace class.

Code from above will output something like this:

0# bar(int) at /path/to/source/file.cpp:70
1# bar(int) at /path/to/source/file.cpp:70
2# bar(int) at /path/to/source/file.cpp:70
3# bar(int) at /path/to/source/file.cpp:70
4# main at /path/to/main.cpp:93
5# __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
6# _start

	Note
By default the Stacktrace library is very conservative in methods to decode stacktrace. If your output does not look as fancy as in example from above, see section "Configuration and Build" for allowing advanced features of the library.

Handle
terminates, aborts and Segmentation Faults

Segmentation Faults and

std::terminate

calls sometimes happen in programs. Programmers usually wish to get as much information
as possible on such incidents, so having a stacktrace will significantly improve debugging and fixing.

std::terminate

calls

std::abort

, so we need to capture stack traces on Segmentation Faults and Abort signals.

	Warning
Writing a signal handler requires high attention! Only a few system calls allowed in signal handlers, so there's no cross platform way to print a stacktrace without a risk of deadlocking. The only way to deal with the problem - dump raw stacktrace into file/socket and parse it on program restart.

Let's write a handler to safely dump stacktrace:

#include <signal.h>     // ::signal, ::raise
#include <boost/stacktrace.hpp>

void my_signal_handler(int signum) {
::signal(signum, SIG_DFL);
boost::stacktrace::safe_dump_to("./backtrace.dump");
::raise(SIGABRT);
}

Registering our handler:

::signal(SIGSEGV, &my_signal_handler);
::signal(SIGABRT, &my_signal_handler);

At program start we check for a file with stacktrace and if it exist - we're writing it in human readable format:

if (boost::filesystem::exists("./backtrace.dump")) {
// there is a backtrace
std::ifstream ifs("./backtrace.dump");

boost::stacktrace::stacktrace st = boost::stacktrace::stacktrace::from_dump(ifs);
std::cout << "Previous run crashed:\n" << st << std::endl;

// cleaning up
ifs.close();
boost::filesystem::remove("./backtrace.dump");
}

Now we'll get the following output on

std::terminate

call after the program restarts:

Previous run crashed:
0# 0x00007F2EC0A6A8EF
1# my_signal_handler(int) at ../example/terminate_handler.cpp:37
2# 0x00007F2EBFD84CB0
3# 0x00007F2EBFD84C37
4# 0x00007F2EBFD88028
5# 0x00007F2EC0395BBD
6# 0x00007F2EC0393B96
7# 0x00007F2EC0393BE1
8# bar(int) at ../example/terminate_handler.cpp:18
9# foo(int) at ../example/terminate_handler.cpp:22
10# bar(int) at ../example/terminate_handler.cpp:14
11# foo(int) at ../example/terminate_handler.cpp:22
12# main at ../example/terminate_handler.cpp:84
13# 0x00007F2EBFD6FF45
14# 0x0000000000402209

	Note
Function names from shared libraries may not be decoded due to address space layout randomization. Still better than nothing.

Better
asserts

Pretty often assertions provide not enough information to locate the problem. For example you can see the following message on out-of-range access:

../../../boost/array.hpp:123: T& boost::array<T, N>::operator[](boost::array<T, N>::size_type) [with T = int; long unsigned int N = 5ul]: Assertion '(i < N)&&("out of range")' failed.
Aborted (core dumped)

That's not enough to locate the problem without debugger. There may be thousand code lines in real world examples and hundred places where that assertion could happen. Let's try to improve the assertions, and make them more informative:

// BOOST_ENABLE_ASSERT_DEBUG_HANDLER is defined for the whole project
#include <stdexcept>    // std::logic_error
#include <iostream>     // std::cerr
#include <boost/stacktrace.hpp>

namespace boost {
inline void assertion_failed_msg(char const* expr, char const* msg, char const* function, char const* /*file*/, long /*line*/) {
std::cerr << "Expression '" << expr << "' is false in function '" << function << "': " << (msg ? msg : "<...>") << ".\n"
<< "Backtrace:\n" << boost::stacktrace::stacktrace() << '\n';
std::abort();
}

inline void assertion_failed(char const* expr, char const* function, char const* file, long line) {
::boost::assertion_failed_msg(expr, 0 /*nullptr*/, function, file, line);
}
} // namespace boost

We've defined the

BOOST_ENABLE_ASSERT_DEBUG_HANDLER

macro for the whole project. Now all the

BOOST_ASSERT

and

BOOST_ASSERT_MSG

will call our functions

assertion_failed

and

assertion_failed_msg

in case of failure. In

assertion_failed_msg

we output information that was provided by the assertion macro and

boost::stacktrace::stacktrace

:

Expression 'i < N' is false in function 'T& boost::array<T, N>::operator[](boost::array<T, N>::size_type) [with T = int; long unsigned int N = 5ul; boost::array<T, N>::reference = int&; boost::array<T, N>::size_type = long unsigned int]': out of range.
Backtrace:
0# boost::assertion_failed_msg(char const*, char const*, char const*, char const*, long) at ../example/assert_handler.cpp:39
1# boost::array<int, 5ul>::operator[](unsigned long) at ../../../boost/array.hpp:124
2# bar(int) at ../example/assert_handler.cpp:17
3# foo(int) at ../example/assert_handler.cpp:25
4# bar(int) at ../example/assert_handler.cpp:17
5# foo(int) at ../example/assert_handler.cpp:25
6# main at ../example/assert_handler.cpp:54
7# 0x00007F991FD69F45 in /lib/x86_64-linux-gnu/libc.so.6
8# 0x0000000000401139

Now we do know the steps that led to the assertion and can find the error without debugger.

Exceptions
with stacktrace

You can provide more information along with exception by embedding stacktraces into the exception. There are many ways to do that, here's how to doe that using Boost.Exception:

Declare a

boost::error_info

typedef that holds the stacktrace:

#include <boost/stacktrace.hpp>
#include <boost/exception/all.hpp>

typedef boost::error_info<struct tag_stacktrace, boost::stacktrace::stacktrace> traced;

Write a helper class for throwing any exception with stacktrace:

template <class E>
void throw_with_trace(const E& e) {
throw boost::enable_error_info(e)
<< traced(boost::stacktrace::stacktrace());
}

Use

throw_with_trace(E);

instead of just

throw
E;

:

if (i >= 4)
throw_with_trace(std::out_of_range("'i' must be less than 4 in oops()"));
if (i <= 0)
throw_with_trace(std::logic_error("'i' must not be greater than zero in oops()"));

Process exceptions:

try {
foo(5); // testing assert handler
} catch (const std::exception& e) {
std::cerr << e.what() << '\n';
const boost::stacktrace::stacktrace* st = boost::get_error_info<traced>(e);
if (st) {
std::cerr << *st << '\n';
}
}

Code from above will output:

'i' must not be greater than zero in oops()
0# void throw_with_trace<std::logic_error>(std::logic_error const&) at ../example/throwing_st.cpp:22
1# oops(int) at ../example/throwing_st.cpp:38
2# bar(int) at ../example/throwing_st.cpp:54
3# foo(int) at ../example/throwing_st.cpp:59
4# bar(int) at ../example/throwing_st.cpp:49
5# foo(int) at ../example/throwing_st.cpp:59
6# main at ../example/throwing_st.cpp:76
7# 0x00007FAC113BEF45 in /lib/x86_64-linux-gnu/libc.so.6
8# 0x0000000000402ED9

Enabling
and disabling stacktraces

At some point arises a requirement to easily enable/disable stacktraces for a whole project. That could be easily achieved.

Just define BOOST_STACKTRACE_LINK for a whole project. Now you can enable/disable stacktraces by just linking with different libraries:

link with

boost_stacktrace_noop

to disable backtracing

link with other

boost_stacktrace_*

libraries

See
section "Configuration and Build" for more info.

Saving
stacktraces by specified format

boost::stacktrace::stacktrace

provides access to individual

frames

of the stacktrace, so that you could save stacktrace information in your own
format. Consider the example, that saves only function addresses of each frame:

#include <boost/stacktrace.hpp>
#include <iostream>     // std::cout

namespace bs = boost::stacktrace;
void dump_compact(const bs::stacktrace& st) {
for (bs::frame frame: st) {
std::cout << frame.address() << ',';
}

std::cout << std::endl;
}

Code from above will output:

0x7fbcfd17f6b5,0x400d4a,0x400d61,0x400d61,0x400d61,0x400d61,0x400d77,0x400cbf,0x400dc0,0x7fbcfc82d830,0x400a79,

Getting
function information from pointer

boost::stacktrace::frame

provides information about functions. You may construct
that class from function pointer and get the function name at runtime:

#include <signal.h>     // ::signal
#include <boost/stacktrace/frame.hpp>
#include <iostream>     // std::cerr
#include <cstdlib>      // std::exit

void print_signal_handler_and_exit() {
typedef void(*function_t)(int);

function_t old_signal_function = ::signal(SIGSEGV, SIG_DFL);
boost::stacktrace::frame f(old_signal_function);
std::cout << f << std::endl;
std::exit(0);
}

Code from above will output:

my_signal_handler(int) at boost/libs/stacktrace/example/debug_function.cpp:21

Global
control over stacktrace output format

You may override the behavior of default stacktrace output operator by defining the macro from Boost.Config

BOOST_USER_CONFIG

to point to a file like following:

#ifndef USER_CONFIG_HPP
#define USER_CONFIG_HPP

#include <boost/stacktrace/stacktrace_fwd.hpp>

#include <iosfwd>

namespace boost { namespace stacktrace {

template <class CharT, class TraitsT, class Allocator>
std::basic_ostream<CharT, TraitsT>& do_stream_st(std::basic_ostream<CharT, TraitsT>& os, const basic_stacktrace<Allocator>& bt);

template <class CharT, class TraitsT>
std::basic_ostream<CharT, TraitsT>& operator<<(std::basic_ostream<CharT, TraitsT>& os, const stacktrace& bt) {
return do_stream_st(os, bt);
}

}}  // namespace boost::stacktrace
#endif // USER_CONFIG_HPP

Implementation of

do_stream_st

may be the following:

namespace boost { namespace stacktrace {

template <class CharT, class TraitsT, class Allocator>
std::basic_ostream<CharT, TraitsT>& do_stream_st(std::basic_ostream<CharT, TraitsT>& os, const basic_stacktrace<Allocator>& bt) {
const std::streamsize w = os.width();
const std::size_t frames = bt.size();
for (std::size_t i = 0; i < frames; ++i) {
os.width(2);
os << i;
os.width(w);
os << "# ";
os << bt[i].name();
os << '\n';
}

return os;
}

}}  // namespace boost::stacktrace

Code from above will output:

Terminate called:
0# bar(int)
1# foo(int)
2# bar(int)
3# foo(int)