Segfault while collecting stacktrace with PIKA_WITH_THREAD_STACK_MMAP=OFF

[msimberg]

When PIKA_WITH_THREAD_STACK_MMAP is disabled, the stack trace collection may segfault in a few of the resource partitioner tests (shutdown_suspended_pus, suspend_thread, suspend_pool). This is reproducible in CI with at least clang 15 and 17, and GCC 12 when they use PIKA_WITH_THREAD_STACK_MMAP=OFF. It's also reproducible locally for me with GCC 14. The failure does not seem to reproduce in debug mode (requires -O1 or higher for failure) or with custom allocators (tested mimalloc, need system for failure).

The quickest way to reproduce the failure is with the shutdown_suspended_pus_test and running it in a loop or multiple times through ctest:

ctest --repeat-until-fail 100 --output-on-failure -R shutdown_suspended_pus

The test should segfault most of the time within a few tens of repetitions.

The backtrace is always:

#0  0x00007ffff7e6898f in uw_frame_state_for () from /nix/store/zw9mmk47hg1cghq34ih0dff8q6ngnlr8-gcc-14.2.0-lib/lib/libgcc_s.so.1
#1  0x00007ffff7e6a85e in _Unwind_Backtrace () from /nix/store/zw9mmk47hg1cghq34ih0dff8q6ngnlr8-gcc-14.2.0-lib/lib/libgcc_s.so.1
#2  0x00007ffff7cb55d7 in pika::debug::detail::stack_trace::trace (array=array@entry=0x7fffec01b120, n=n@entry=22) at /home/mjs/src/pika/libs/pika/debugging/src/backtrace.cpp:117
#3  0x00007ffff7d3c0df in pika::debug::detail::backtrace::backtrace (this=0x7fffec262150, frames_no=22) at /nix/store/zzffrygpx8l7wk3falwrj206yyv6akgy-gcc-14.2.0/include/c++/14.2.0/bits/stl_iterator.h:1067
#4  pika::debug::detail::trace[abi:cxx11](unsigned long) (frames_no=20) at /home/mjs/src/pika/libs/pika/debugging/include/pika/debugging/detail/backtrace.hpp:109
#5  pika::detail::custom_exception_info (func=..., file=..., line=1420, auxinfo=...) at /home/mjs/src/pika/libs/pika/runtime/src/custom_exception_info.cpp:335
#6  0x00007ffff7cf3e77 in std::__invoke_impl<pika::exception_info, pika::exception_info (*&)(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, st
d::allocator<char> > const&, long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&), std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<c
har, std::char_traits<char>, std::allocator<char> > const&, long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&> (__f=<optimized out>)
    at /nix/store/zzffrygpx8l7wk3falwrj206yyv6akgy-gcc-14.2.0/include/c++/14.2.0/bits/invoke.h:61
#7  std::__invoke_r<pika::exception_info, pika::exception_info (*&)(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > cons
t&, long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&), std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<cha
r>, std::allocator<char> > const&, long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&> (__fn=<optimized out>)
    at /nix/store/zzffrygpx8l7wk3falwrj206yyv6akgy-gcc-14.2.0/include/c++/14.2.0/bits/invoke.h:116
#8  std::_Function_handler<pika::exception_info(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, long, std::__cxx
11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&), pika::exception_info (*)(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_trait
s<char>, std::allocator<char> > const&, long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>::_M_invoke (__functor=..., __args#0=..., __args#1=..., __args#2=<optimized out>, __args#3=...)
    at /nix/store/zzffrygpx8l7wk3falwrj206yyv6akgy-gcc-14.2.0/include/c++/14.2.0/bits/std_function.h:291
#9  0x00007ffff7cc5a95 in std::function<pika::exception_info(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, lon
g, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>::operator() (this=0x7ffff7e31360 <pika::detail::custom_exception_info_handler>, __args#0=..., __args#1=..., __args#2=<optimized out>, __args#3=...)
    at /nix/store/zzffrygpx8l7wk3falwrj206yyv6akgy-gcc-14.2.0/include/c++/14.2.0/bits/std_function.h:587
#10 pika::detail::construct_custom_exception<pika::exception> (e=..., func=..., file=..., line=1420, auxinfo=...) at /home/mjs/src/pika/libs/pika/errors/src/exception.cpp:202
#11 pika::detail::get_exception<pika::exception> (e=..., func=..., file=..., line=line@entry=1420, auxinfo=...) at /home/mjs/src/pika/libs/pika/errors/src/exception.cpp:238
#12 0x00007ffff7cc5bae in pika::detail::throw_exception<pika::exception> (e=..., func=..., file=..., line=line@entry=1420) at /home/mjs/src/pika/libs/pika/errors/src/exception.cpp:247
#13 0x00007ffff7cbdf6a in pika::detail::throw_exception (errcode=<optimized out>, msg=..., func=..., file=..., line=1420) at /home/mjs/src/pika/libs/pika/errors/src/throw_exception.cpp:24
#14 0x00007ffff7cbfefd in pika::detail::throws_if (ec=..., errcode=pika::error::invalid_status, msg=..., func=..., file=..., line=1420) at /home/mjs/src/pika/libs/pika/errors/src/throw_exception.cpp:54
#15 0x00007ffff7d59ec3 in pika::threads::detail::scheduled_thread_pool<pika::threads::detail::static_priority_queue_scheduler<std::mutex, pika::threads::detail::lockfree_fifo, pika::threads::detail::lockfree_fifo, pika::threads::detail::loc
kfree_fifo> >::suspend_processing_unit_direct (this=0x44dad0, virt_core=0, ec=...) at /home/mjs/src/pika/libs/pika/thread_pools/include/pika/thread_pools/scheduled_thread_pool_impl.hpp:1420
#16 0x0000000000403c45 in pika_main () at /home/mjs/src/pika/libs/pika/resource_partitioner/tests/unit/shutdown_suspended_pus.cpp:48

i.e. comes from libstdc++'s unwind functionality.

A quick test with libunwind (https://www.nongnu.org/libunwind/man/libunwind(3).html, see "Local Unwinding") does not seem to have the same problem, so we could consider adding libunwind support (optional?) for stacktraces.