[PATCH][_GLIBCXX_DEBUG] libbacktrace integration

[François Dumont]

Is it too early to consider this patch ? Or just lack of time ?

Considering the patch I would really appreciate that, if validated, it 
gets in as early as possible in next release.

Thanks,
François

On 24/04/21 3:46 pm, François Dumont wrote:
> Hi
>
>     Here is the patch to add backtrace generation on _GLIBCXX_DEBUG 
> assertions thanks to libbacktrace.
>
>     In addition to this integration I am also improving the generation 
> of the assertion message thanks to the "%.*s" printf format, it avoids 
> an intermediate buffer most of the time. I am also removing the "__" 
> used for uglification to get a nicer output. I can propose it in a 
> dedicated patch if you prefer.
>
>     I am adding GLIBCXX_3.4.30 abi version to properly export the 2 
> new weak symbols. Let me know if it isn't necessary.
>
>     libstdc++: [_GLIBCXX_DEBUG] Add backtrace generation thanks to 
> libbacktrace
>
>       Add _GLIBCXX_DEBUG_BACKTRACE macro to activate backtrace 
> generation on
>     _GLIBCXX_DEBUG assertions using libbacktrace.
>
>             * config/abi/pre/gnu.ver: Add GLIBCXX_3.4.30 version and 
> new exports.
>             * include/debug/formatter.h [_GLIBCXX_DEBUG_BACKTRACE]:
>             Include <backtrace-supported.h>.
>             [_GLIBCXX_DEBUG_BACKTRACE && BACKTRACE_SUPPORTED]:
>             Include <backtrace.h>.
>             [(!_GLIBCXX_DEBUG_BACKTRACE || !BACKTRACE_SUPPORTED) &&
>             _GLIBCXX_USE_C99_STDINT_TR1]: Include <stdint.h>.
>             [_GLIBCXX_DEBUG_USE_LIBBACKTRACE]
>             (__gnu_debug::__create_backtrace_state): New.
>             [_GLIBCXX_DEBUG_USE_LIBBACKTRACE]
>             (__gnu_debug::__render_backtrace): New.
> [_GLIBCXX_DEBUG_USE_LIBBACKTRACE](_Error_formatter::_M_print_backtrace):
>             New.
> [_GLIBCXX_DEBUG_USE_LIBBACKTRACE](_Error_formatter::_M_backtrace_state):
>             New.
>             (_Error_formatter::_Error_formatter): Outline definition.
>             * src/c++11/debug.cc: Include <cstring>.
>             (_Print_func_t): New.
>             (print_word): Use '%.*s' format in fprintf to render only 
> expected
>             number of chars.
>             (print_raw(PrintContext&, const char*, ptrdiff_t)): New.
>             (print_function(PrintContext&, const char*, 
> _Print_func_t)): New.
>             (print_type): Use latter.
>             (print_string(PrintContext&, const char*, const 
> _Parameter*, size_t)):
>             Change signature to...
>             (print_string(PrintContext&, const char*, ptrdiff_t, const 
> _Parameter*,
>             size_t)): ...this and adapt. Remove intermediate buffer to 
> render input
>             string.
>             (print_string(PrintContext&, const char*, ptrdiff_t)): New.
>             [_GLIBCXX_DEBUG_USE_LIBBACKTRACE]
>             (print_backtrace(void*, uintptr_t, const char*, int, const 
> char*)): New.
>             (_Error_formatter::_M_error()): Adapt.
>             [_GLIBCXX_DEBUG_USE_LIBBACKTRACE]
>             (__gnu_debug::__create_backtrace_state): New, weak symbol.
>             [_GLIBCXX_DEBUG_USE_LIBBACKTRACE]
>             (__gnu_debug::__render_backtrace): New, weak symbol.
>             * testsuite/util/testsuite_abi.cc: Add new symbol version.
>             * doc/xml/manual/debug_mode.xml: Document 
> _GLIBCXX_DEBUG_BACKTRACE.
>             * doc/xml/manual/using.xml: Likewise.
>
> Tested under Linux x86_64.
>
> Ok to commit ?
>
> François
>