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From: "ndesaulniers at google dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/110728] New: should __attribute__((cleanup())) callback get
 invoked for indirect edges of asm goto
Date: Tue, 18 Jul 2023 21:23:51 +0000
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X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110728

            Bug ID: 110728
           Summary: should __attribute__((cleanup())) callback get invoked
                    for indirect edges of asm goto
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ndesaulniers at google dot com
  Target Milestone: ---

Consider the following test case:

```c
void test4cleanup(int*);
// No errors expected.
void test4(void) {
l0:;
    int x __attribute__((cleanup(test4cleanup)));
    asm goto("# %l0"::::l0);
}

```

gcc trunk today generates effectively the following control flow:
```
test4:
.LFB0:
        subq    $24, %rsp
.L2:
#APP
        # .L2
#NO_APP
        leaq    12(%rsp), %rdi
        call    test4cleanup
        addq    $24, %rsp
        ret
```
so if the inline asm blob jumps to `l0`, then the cleanup function is not r=
un.

That seemed surprising, at least when we discussed it on this thread.
https://reviews.llvm.org/D155342#4511887

A fellow Linux kernel dev (who introduced the usage of
__attribute__((cleanup())) (and asm goto, coincidentally) to the kernel) ag=
reed
(on IRC).

For now in clang, we produce a diagnostic since the behavior seems surprisi=
ng.=20
If this gets changed in GCC, I'd be happy to modify clang to match that upd=
ated
behavior.=