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Library for getting stacktraces from arbitrary exceptions (#147)
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‎build/Jamfile.v2‎

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@@ -132,4 +132,15 @@ lib boost_stacktrace_windbg_cached
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#<link>shared:<define>BOOST_STACKTRACE_DYN_LINK=1
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;
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boost-install boost_stacktrace_noop boost_stacktrace_backtrace boost_stacktrace_addr2line boost_stacktrace_basic boost_stacktrace_windbg boost_stacktrace_windbg_cached ;
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lib boost_stacktrace_from_exception
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: # sources
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../src/from_exception.cpp
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: # requirements
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<warnings>all
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<target-os>linux:<library>dl
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: # default build
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: # usage-requirements
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#<link>shared:<define>BOOST_STACKTRACE_DYN_LINK=1
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;
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boost-install boost_stacktrace_noop boost_stacktrace_backtrace boost_stacktrace_addr2line boost_stacktrace_basic boost_stacktrace_windbg boost_stacktrace_windbg_cached boost_stacktrace_from_exception ;

‎doc/stacktrace.qbk‎

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@@ -128,6 +128,64 @@ Generic recommendation is to *avoid signal handlers! Use* platform specific ways
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]
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[endsect]
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[section Stacktrace from arbitrary exception]
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[warning At the moment the functionality is only available for some of the
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popular cxx run-times for POSIX systems. Make sure that your platform
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is supported by running some tests.
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]
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The library provides a way to get stacktrace from an exception as if the
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stacktrace was captured at the point the exception was thrown. Works even if
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the exception was thrown from a third party binary library.
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Link with
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`boost_stacktrace_from_exception` library (or just `LD_PRELOAD` it!) and call
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boost::stacktrace::stacktrace::from_current_exception() to get the trace:
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```
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#include <iostream>
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#include <stdexcept>
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#include <string_view>
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#include <boost/stacktrace.hpp>
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void foo(std::string_view key);
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void bar(std::string_view key);
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int main() {
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try {
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foo("test1");
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bar("test2");
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} catch (const std::exception& exc) {
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boost::stacktrace::stacktrace trace = std::stacktrace::from_current_exception(); // <---
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std::cerr << "Caught exception: " << exc.what() << ", trace:\n" << trace;
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}
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}
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```
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The output of the above sample may be the following:
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```
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Caught exception: std::map::at, trace:
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0# get_data_from_config(std::string_view) at /home/axolm/basic.cpp:600
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1# bar(std::string_view) at /home/axolm/basic.cpp:6
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2# main at /home/axolm/basic.cpp:17
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```
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With the above technique a developer can locate the source file and the function
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that has thrown the exception without a debugger help. it is especially useful
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for testing in containers (github CI, other CIs), where the developer has no
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direct access to the testing environment and reproducing the issue is
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complicated.
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Note that linking with `boost_stacktrace_from_exception` may increase memory
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consumption of the application, as the exceptions now additionally store traces.
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At runtime switch boost::stacktrace::this_thread::set_capture_stacktraces_at_throw()
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allows to disable/enable capturing and storing traces in exceptions.
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[endsect]
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133191

@@ -342,6 +400,8 @@ In order of helping and advising:
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* Great thanks to Nat Goodspeed for requesting [classref boost::stacktrace::frame] like class.
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* Great thanks to Niall Douglas for making an initial review, helping with some platforms and giving great hints on library design.
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* Great thanks to all the library reviewers.
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* Great thanks to Andrei Nekrashevich for prototyping the idea of stacktraces
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from arbitrary exception in `libsfe`.
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[endsect]
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‎include/boost/stacktrace.hpp‎

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@@ -13,7 +13,8 @@
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#endif
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#include <boost/stacktrace/frame.hpp>
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#include <boost/stacktrace/stacktrace.hpp> // Actually already includes all the headers
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#include <boost/stacktrace/stacktrace.hpp>
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#include <boost/stacktrace/safe_dump_to.hpp>
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#include <boost/stacktrace/this_thread.hpp>
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#endif // BOOST_STACKTRACE_HPP

‎include/boost/stacktrace/stacktrace.hpp‎

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@@ -35,6 +35,20 @@
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namespace boost { namespace stacktrace {
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namespace impl {
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#if defined(__GNUC__) && defined(__ELF__)
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BOOST_NOINLINE BOOST_SYMBOL_VISIBLE __attribute__((weak))
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const char* current_exception_stacktrace() noexcept;
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BOOST_NOINLINE BOOST_SYMBOL_VISIBLE __attribute__((weak))
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bool& ref_capture_stacktraces_at_throw() noexcept;
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#endif
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} // namespace impl
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/// Class that on construction copies minimal information about call stack into its internals and provides access to that information.
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/// @tparam Allocator Allocator to use during stack capture.
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template <class Allocator>
@@ -65,7 +79,7 @@ class basic_stacktrace {
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}
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BOOST_NOINLINE void init(std::size_t frames_to_skip, std::size_t max_depth) {
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BOOST_CONSTEXPR_OR_CONST std::size_t buffer_size = 128;
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constexpr std::size_t buffer_size = 128;
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if (!max_depth) {
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return;
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}
@@ -340,6 +354,44 @@ class basic_stacktrace {
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return ret;
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}
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/// Returns a basic_stacktrace object containing a stacktrace captured at
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/// the point where the currently handled exception was thrown by its
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/// initial throw-expression (i.e. not a rethrow), or an empty
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/// basic_stacktrace object if:
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///
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/// - the `boost_stacktrace_from_exception` library is not linked to the
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/// current binary, or
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/// - the initialization of stacktrace failed, or
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/// - stacktrace captures are not enabled for the throwing thread, or
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/// - no exception is being handled, or
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/// - due to implementation-defined reasons.
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///
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/// `alloc` is passed to the constructor of the stacktrace object.
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/// Rethrowing an exception using a throw-expression with no operand does
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/// not alter the captured stacktrace.
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///
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/// Implements https://wg21.link/p2370r1
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static basic_stacktrace<Allocator> from_current_exception(const allocator_type& alloc = allocator_type()) noexcept {
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// Matches the constant from implementation
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constexpr std::size_t kStacktraceDumpSize = 4096;
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const char* trace = nullptr;
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#if defined(__GNUC__) && defined(__ELF__)
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if (impl::current_exception_stacktrace) {
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trace = impl::current_exception_stacktrace();
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}
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#endif
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if (trace) {
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try {
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return basic_stacktrace<Allocator>::from_dump(trace, kStacktraceDumpSize, alloc);
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} catch (const std::exception&) {
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// ignore
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}
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}
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return basic_stacktrace<Allocator>{0, 0, alloc};
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}
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};
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/// @brief Compares stacktraces for less, order is platform dependent.

‎include/boost/stacktrace/this_thread.hpp‎

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@@ -0,0 +1,54 @@
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// Copyright Antony Polukhin, 2023-2024.
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_STACKTRACE_THIS_THREAD_HPP
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#define BOOST_STACKTRACE_THIS_THREAD_HPP
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#include <boost/config.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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# pragma once
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#endif
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#include <boost/stacktrace/stacktrace.hpp>
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namespace boost { namespace stacktrace { namespace this_thread {
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/// @brief Invoking the function with the enable parameter equal to `true`
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/// enables capturing of stacktraces by the current thread of execution at
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/// exception object construction if the `boost_stacktrace_from_exception`
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/// library is linked to the current binary; disables otherwise.
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///
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/// Implements https://wg21.link/p2370r1
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inline void set_capture_stacktraces_at_throw(bool enable = true) noexcept {
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#if defined(__GNUC__) && defined(__ELF__)
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if (impl::ref_capture_stacktraces_at_throw) {
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impl::ref_capture_stacktraces_at_throw() = enable;
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}
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#endif
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(void)enable;
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}
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/// @return whether the capturing of stacktraces by the current thread of
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/// execution is enabled and
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/// boost::stacktrace::basic_stacktrace::from_current_exception may return a
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/// non empty stacktrace.
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///
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/// Returns true if set_capture_stacktraces_at_throw(false) was not called
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/// and the `boost_stacktrace_from_exception` is linked to the current binary.
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///
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/// Implements https://wg21.link/p2370r1
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inline bool get_capture_stacktraces_at_throw() noexcept {
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#if defined(__GNUC__) && defined(__ELF__)
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if (impl::ref_capture_stacktraces_at_throw) {
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return impl::ref_capture_stacktraces_at_throw();
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}
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#endif
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return false;
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}
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}}} // namespace boost::stacktrace::this_thread
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#endif // BOOST_STACKTRACE_THIS_THREAD_HPP

‎src/exception_headers.h‎

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// Copyright Antony Polukhin, 2023-2024.
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#include <stddef.h>
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#if defined(__x86_64__) || defined(_M_X64) || defined(__MINGW32__)
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#define BOOST_STACKTRACE_ALWAYS_STORE_IN_PADDING 1
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#else
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#define BOOST_STACKTRACE_ALWAYS_STORE_IN_PADDING 0
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#endif
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extern "C" {
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// Developer note: helper to experiment with layouts of different
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// exception headers https://godbolt.org/z/rrcdPbh1P
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// https://github.com/llvm/llvm-project/blob/b3dd14ce07f2750ae1068fe62abbf2f3bd2cade8/libcxxabi/src/cxa_exception.h
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struct cxa_exception_begin_llvm {
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const char* reserve;
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size_t referenceCount;
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};
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static cxa_exception_begin_llvm* exception_begin_llvm_ptr(void* ptr) {
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size_t kExceptionBeginOffset = (
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sizeof(void*) == 8 ? 128 : 80
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);
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return (cxa_exception_begin_llvm*)((char*)ptr - kExceptionBeginOffset);
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}
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// https://github.com/gcc-mirror/gcc/blob/5d2a360f0a541646abb11efdbabc33c6a04de7ee/libstdc%2B%2B-v3/libsupc%2B%2B/unwind-cxx.h#L100
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struct cxa_exception_begin_gcc {
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size_t referenceCount;
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const char* reserve;
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};
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static cxa_exception_begin_gcc* exception_begin_gcc_ptr(void* ptr) {
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size_t kExceptionBeginOffset = (
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sizeof(void*) == 8 ? 128 : 96
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);
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return (cxa_exception_begin_gcc*)((char*)ptr - kExceptionBeginOffset);
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}
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static void* get_current_exception_raw_ptr(void* exc_ptr) {
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// https://github.com/gcc-mirror/gcc/blob/16e2427f50c208dfe07d07f18009969502c25dc8/libstdc%2B%2B-v3/libsupc%2B%2B/eh_ptr.cc#L147
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return *static_cast<void**>(exc_ptr);
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}
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} // extern "C"
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