[Bug c/114205] New: Miscompilation: the use of __builtin_object_size cause asan failure.

[Bug c/114205] New: Miscompilation: the use of __builtin_object_size cause asan failure.

[141242068 at smail dot nju.edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114205

            Bug ID: 114205
           Summary: Miscompilation: the use of __builtin_object_size cause
                    asan failure.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 141242068 at smail dot nju.edu.cn
  Target Milestone: ---

This program:
```
#include <stdlib.h>

static char a[40];

int main() {
  if (__builtin_object_size(&a[0] + 1, 1) == (size_t)-1)
    __builtin_abort();
  return 0;
}
```

When compiled with `gcc -fsanitize=address`, the result binary reports error.
But if change the branch compare operator from "==" into "!=", then result
binary compiled from `gcc -fsanitize=address` reports nothing.

Error with "==", can be verified on https://gcc.godbolt.org/z/vWxWhYoMT
Normal with "!=", can be verified on https://gcc.godbolt.org/z/sb4bGs76f

[Bug c/114205] Miscompilation: the use of __builtin_object_size cause asan failure.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114205

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't see why you think this is a bug.

-1 returning from __builtin_object_size means it does not know the size.

Without optimization, GCC cannot figure out the size of the object that is
being passed to __builtin_object_size . So at -O0 it aborts.
`-fsanitize=address` will output the error message:
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==1==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x7f7a49828898 bp
0x7f7a49a1be90 sp 0x7ffc8a097720 T0)

```

When abort is called.

There is nothing wrong here.