https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38534
--- Comment #9 from Lukas Grätz <lukas.gra...@tu-darmstadt.de> ---
(In reply to H.J. Lu from comment #8)
> (In reply to Lukas Grätz from comment #7)
> > (In reply to H.J. Lu from comment #4)
> > > When I compiled __cxxabiv1::__cxa_throw, which is a noreturn function in
> > > libstdc++-v3/libsupc++/eh_throw.cc not to save callee-saved registers,
> > > most of C++ exception tests crashed.
> >
> > Can you tell how you compiled it? Thanks in advance!
>
> I have a patch to fix it. Please try users/hjl/pr113312/gcc-13 branch:
>
>
> For your testcase, I got
Well it is not my testcase. But I added backtracing and observed that the
printed backtrace is unchanged with your patch. The new no_return_to_caller():
void __attribute__((noreturn))
no_return_to_caller(int a, int b, int c, int d)
{
LOOP_BODY;
#define BT_BUF_SIZE 100
void *buffer[BT_BUF_SIZE];
backtrace_symbols_fd(buffer, backtrace(buffer, BT_BUF_SIZE), STDOUT_FILENO);
while (1);
}
What I observed from the assembly is that %rbp is not saved, whereas %rip and
%rsp are still implicitly saved by the call instruction. But since glibc's
backtrace implementation does not use %rbp, this is fine.
Some amateur speculation, just ignore it: I don't know whether %rbp is the
source of the failed C++ test cases, which also do some stack unwinding. After
looking in the System V Abi specification I am still unsure whether stack
unwinding relies on %rbp or not. Perhaps there is an unnecessary dependency on
%rbp or a missing "-fno-omit-frame-pointer" somewhere in the gcc internals that
causes the problem.
