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From: "rjmccall at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110728] should __attribute__((cleanup())) callback get invoked for indirect edges of asm goto
Date: Wed, 19 Jul 2023 17:16:55 +0000 [thread overview]
Message-ID: <bug-110728-4-KuAKVv0zQj@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110728-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110728
--- Comment #8 from John McCall <rjmccall at gmail dot com> ---
> Let me clarify. If GCC were change behavior of `asm goto` to
> invoke the destructor/cleanup function before the backwards edge
> of `asm goto`, I would submit a patch to clang to implement that
> behavior as well.
Ah, thank you, I understand what you're saying now. Yes, we would take that.
I think this test case might be a little more illuminating and separates out
the issue of the back-edge and the uninitialized variable:
https://godbolt.org/z/doG7414va
```
#include <malloc.h>
#define GOTO 1
#define COMPUTED_GOTO 2
#define ASM_GOTO 3
#define CASE ASM_GOTO
static void free_from(int **ptr) {
free(*ptr);
}
int test() {
#if CASE == COMPUTED_GOTO
void *lbl = &&label;
#endif
if (1) {
__attribute__((cleanup(free_from))) int *p = calloc(sizeof(int), 1);
#if CASE == GOTO
goto label;
#elif CASE == COMPUTED_GOTO
goto *lbl;
#elif CASE == ASM_GOTO
asm goto("<<< asm goto %l0 >>>"::::label);
#endif
}
label:
return 0;
}
```
GCC produces this output for CASE == ASM_GOTO (stripping the .LFB labels):
```
test:
push rbp
mov rbp, rsp
sub rsp, 16
mov esi, 1
mov edi, 4
call calloc
mov QWORD PTR [rbp-8], rax
<<< asm goto .L3 >>>
lea rax, [rbp-8]
mov rdi, rax
call free_from
.L3:
mov eax, 0
leave
ret
``
It does something similar for CASE == COMPUTED_GOTO. In both cases, the branch
avoids the cleanup with no diagnostic. But it does the right thing with CASE
== GOTO.
next prev parent reply other threads:[~2023-07-19 17:16 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-18 21:23 [Bug c/110728] New: " ndesaulniers at google dot com
2023-07-18 21:29 ` [Bug c/110728] " pinskia at gcc dot gnu.org
2023-07-18 21:32 ` pinskia at gcc dot gnu.org
2023-07-18 21:33 ` pinskia at gcc dot gnu.org
2023-07-18 21:48 ` pinskia at gcc dot gnu.org
2023-07-18 23:22 ` rjmccall at gmail dot com
2023-07-19 7:01 ` rguenth at gcc dot gnu.org
2023-07-19 16:46 ` [Bug middle-end/110728] " ndesaulniers at google dot com
2023-07-19 17:16 ` rjmccall at gmail dot com [this message]
2023-08-03 14:38 ` matz at gcc dot gnu.org
2023-08-03 16:00 ` ndesaulniers at google dot com
2023-08-03 16:11 ` matz at gcc dot gnu.org
2023-08-03 17:07 ` rjmccall at gmail dot com
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