https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89003
Bug ID: 89003
Summary: Return inside a statement expression while
initializing a static local variable fails to cleanup
cxa_guard
Product: gcc
Version: 5.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: wilkey at drive dot ai
Target Milestone: ---
consider the following:
void f() {
static int i = ({
if (true) return;
42;
});
}
g++ -g yields:
0x0000000000400606 <+0>: push %rbp
0x0000000000400607 <+1>: mov %rsp,%rbp
0x000000000040060a <+4>: mov $0x601040,%eax
0x000000000040060f <+9>: movzbl (%rax),%eax
0x0000000000400612 <+12>: test %al,%al
0x0000000000400614 <+14>: jne 0x40062a <f()+36>
0x0000000000400616 <+16>: mov $0x601040,%edi
0x000000000040061b <+21>: callq 0x4004e0 <__cxa_guard_acquire@plt>
0x0000000000400620 <+26>: test %eax,%eax
0x0000000000400622 <+28>: setne %al
0x0000000000400625 <+31>: test %al,%al
0x0000000000400627 <+33>: je 0x40062a <f()+36>
0x0000000000400629 <+35>: nop
0x000000000040062a <+36>: pop %rbp
0x000000000040062b <+37>: retq
Note that nothing is emitted to release the guard (neither
__cxa_guard_release() nor __cxa_guard_abort()).
The next caller of the function will either SIGABRT if on the same thread
(deadlock detection algorithm) or block forever if another thread.
Slightly more complex examples include __cxa_guard_release for cases that don't
return early, but if the early return path is taken, the emitted code will
still just JMP right over it.
