libbacktrace integration for _GLIBCXX_DEBUG mode

François Dumont frs.dumont@gmail.com
Mon Dec 10 23:08:00 GMT 2018 

Hi

     Here is the integration of libbacktrace to provide the backtrace on 
_GLIBCXX_DEBUG assertions.

     I decided to integrate it without impacting the build scripts. 
Users just need to install libbacktrace and once done _GLIBCXX_DEBUG 
will look for it and start using it if supported. The drawback is that 
as soon as libbacktrace is installed users will have to add -lbacktrace 
in order to use _GLIBCXX_DEBUG mode. But I expect that if you install 
libbacktrace it is for a reason.

     Note that when libbacktrace is not supported I include stdint.h to 
get uintptr_t, I hope it is the correct way to get it in a portable way.

     I also explcitely define BACKTRACE_SUPPORTED to 0 to make sure 
libstdc++ has no libbacktrace dependency after usual build.

     As it starts to make a lot of information displayed on Debug 
assertion I have created print_function to filter output of functions. 
It removes things like __cxx1998::, std::allocator and greatly 
simplified _Safe_iterator rendering.

     Here is an example of output when building 
23_containers/vector/debug/construct3_neg.cc:

/home/fdt/dev/gcc/install/include/c++/9.0.0/debug/safe_iterator.h:321:
In function:
     __gnu_debug::_Safe_iterator<_Iterator, _Sequence, _Category>&
     __gnu_debug::_Safe_iterator<_Iterator, _Sequence,
     _Category>::operator++() [with _Iterator = std::_List_iterator<int>;
     _Sequence = std::__debug::list<int>; _Category =
     std::forward_iterator_tag]

Backtrace:
     0x40275f 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>::operator++()
/home/fdt/dev/gcc/install/include/c++/9.0.0/debug/safe_iterator.h:321
     0x402181 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>::operator++()
/home/fdt/dev/gcc/install/include/c++/9.0.0/debug/safe_iterator.h:570
     0x404082 
std::iterator_traits<__gnu_debug::_Safe_iterator<std::_List_iterator<int>> 
 >::difference_type 
std::__distance<__gnu_debug::_Safe_iterator<std::_List_iterator<int>> 
 >(__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
std::input_iterator_tag)
/home/fdt/dev/gcc/install/include/c++/9.0.0/bits/stl_iterator_base_funcs.h:89
     0x403795 
std::iterator_traits<__gnu_debug::_Safe_iterator<std::_List_iterator<int>> 
 >::difference_type 
std::distance<__gnu_debug::_Safe_iterator<std::_List_iterator<int>> 
 >(__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>)
/home/fdt/dev/gcc/install/include/c++/9.0.0/bits/stl_iterator_base_funcs.h:141
     0x4030b9 void 
std::vector<int>::_M_range_initialize<__gnu_debug::_Safe_iterator<std::_List_iterator<int>> 
 >(__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
std::forward_iterator_tag)
/home/fdt/dev/gcc/install/include/c++/9.0.0/bits/stl_vector.h:1541
     0x402a2d 
std::vector<int>::vector<__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
void>(__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>)
/home/fdt/dev/gcc/install/include/c++/9.0.0/bits/stl_vector.h:618
     0x4022ec 
std::__debug::vector<int>::vector<__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
void>(__gnu_debug::_Safe_iterator<std::_List_iterator<int>>, 
__gnu_debug::_Safe_iterator<std::_List_iterator<int>>)
     /home/fdt/dev/gcc/install/include/c++/9.0.0/debug/vector:195
     0x401e2c void 
__gnu_test::check_construct3<std::__debug::vector<int> >()
     ./util/debug/checks.h:234
     0x401460 test01()
     /home/fdt/dev/poc/construct3_neg.cc:26
     0x40146c main
     /home/fdt/dev/poc/construct3_neg.cc:31

Error: attempt to increment a past-the-end iterator.

Objects involved in the operation:
     iterator "this" @ 0x0x7fff068adce0 {
       type = std::_List_iterator<int> (mutable iterator);
       state = past-the-end;
       references sequence with type 'std::__debug::list<int>' @ 
0x0x7fff068ae080
     }

     * include/debug/formatter.h: Check for backtrace-supported.h access
     and include it.
     [BACKTRACE_SUPPORTED] Include <backtrace.h>
     (_Error_formatter::_Bt_full_t): New function pointer type.
     (_Error_formatter::_M_backtrace_state): New.
     (_Error_formatter::_M_backtrace_full_func): New.
     * src/c++11/debug.cc: Include <cstring>.
     (PrintContext::_M_demangle_name): New.
     (_Print_func_t): New.
     (print_word(PrintContext&, const char*)): New.
     (print_raw(PrintContext&, const char*)): New.
     (print_function(PrintContext&, const char*, _Print_func_t)): New.
     (print_type): Use latter.
     (print_string(PrintContext&, const char*)): New.
     (print_backtrace(void*, uintptr_t, const char*, int, const char*)):
     New.
     (_Error_formatter::_M_error()): Adapt.

Tested under Linux x86_64.

Ok to commit ? One day ?

François


-------------- next part --------------
A non-text attachment was scrubbed...
Name: libbacktrace.patch
Type: text/x-patch
Size: 10654 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20181210/dd7ede72/attachment.bin>

More information about the Libstdc++ mailing list