https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103629
--- Comment #9 from Mathieu Malaterre <mathieu.malaterre at gmail dot com> ---
Compiling the reduce test case without pthread lead to some kind of exception:
```
(gdb) bt full
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:49
set = {__val = {0 <repeats 12 times>, 8245935278387129975,
5908832823118463008, 0, 0}}
pid = <optimized out>
tid = <optimized out>
ret = <optimized out>
#1 0x00007ffff7bf9536 in __GI_abort () at abort.c:79
save_stage = 1
act = {__sigaction_handler = {sa_handler = 0x7ffff7d925e0
<_IO_2_1_stderr_>, sa_sigaction = 0x7ffff7d925e0 <_IO_2_1_stderr_>}, sa_mask =
{__val = {140737350282933, 140737351591392, 140737351591392,
140737351591523, 140737351595200, 3432, 140737350279750, 11, 1,
140737351591392, 93824992325712, 140737352586656, 140737488347968, 0,
140737350287193, 140737351591840}}, sa_flags = -135945484,
sa_restorer = 0x7ffff7d927a0 <stderr>}
sigs = {__val = {32, 0, 0, 0, 17, 9223372036854775922, 140737352422480,
140737350282933, 0, 140737350282933, 140737353353159, 140737351591392,
93824992325672, 140737351595200, 3432, 140737350279750}}
#2 0x00007ffff7e4f87a in __gnu_cxx::__verbose_terminate_handler () at
../../../../src/libstdc++-v3/libsupc++/vterminate.cc:95
terminating = true
t = <optimized out>
#3 0x00007ffff7e5b04a in __cxxabiv1::__terminate (handler=<optimized out>) at
../../../../src/libstdc++-v3/libsupc++/eh_terminate.cc:48
No locals.
#4 0x00007ffff7e5b0b5 in std::terminate () at
../../../../src/libstdc++-v3/libsupc++/eh_terminate.cc:58
No locals.
#5 0x00007ffff7e5b349 in __cxxabiv1::__cxa_throw (obj=<optimized out>,
tinfo=0x7ffff7fb1530 <typeinfo for std::system_error>, dest=0x7ffff7e855a0
<std::system_error::~system_error()>)
at ../../../../src/libstdc++-v3/libsupc++/eh_throw.cc:95
globals = <optimized out>
header = 0x55555556aeb0
#6 0x00007ffff7e525fa in std::__throw_system_error(int) () from
/usr/lib/x86_64-linux-gnu/libstdc++.so.6
No symbol table info available.
#7 0x00007ffff7fc740f in
std::call_once<Tree::treeType()::{lambda()#1}>(std::once_flag&,
Tree::treeType()::{lambda()#1}&&) (__once=..., __f=...) at
/usr/include/c++/11/mutex:784
__e = -1
__callable = {____f = @0x7fffffffe3ff}
__exec = {<No data fields>}
```
I am not able to reproduce gcc behavior using clang++ (again Debian sid
version).
