Debug Mode ENH 3/4: Add backtrace

[Jonathan Wakely]

On 08/05/18 16:51 -0700, Ian Lance Taylor via libstdc++ wrote:
>On Tue, May 8, 2018 at 12:54 PM, François Dumont <frs.dumont@gmail.com> wrote:
>>
>> I'll go with this version for now but I'll look into libbacktrace.
>>
>> It will be perhaps the occasion to play with autoconf & al tools to find out
>> if I can use libbacktrace.
>
>In GCC libgo and libgfortran already use libbacktrace, so there are
>good examples to copy.

And if there are any concerns about adding an extra dependency to
libstdcOO.so or increasing the size of libstdc++.a we could
conditionally use libbacktrace for the unoptimized versions of libstdc++
installed into $libdir/debug/ when --enable-libstdcxx-debug is used
(which is orthogonal to the Debug Mode).

That would allow getting nicer backtraces by linking to the debug
libs, without adding an unconditional dependency that is only used by
code compiled with _GLIBCXX_DEBUG.