https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99098
Peter Ross <pross at xvid dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pross at xvid dot org
--- Comment #2 from Peter Ross <pross at xvid dot org> ---
The following test case produces a -Wfree-nonheap-object false positive. I
argue that the memory being free'd is heap memory. It is offset by one to
accomodate the negative offset applied immediately after malloc.
```
#include <stdlib.h>
char * knn_alloc()
{
char * w = malloc(sizeof(char));
if (!w)
return NULL;
return w - 1;
}
void knn_free(char * w)
{
free(w + 1);
}
int main()
{
char * w = knn_alloc();
if (!w)
return -1;
knn_free(w);
return 0;
}
```
```
$ gcc knn.c -save-temps
knn.c: In function ‘knn_free’:
knn.c:11:5: warning: ‘free’ called on pointer ‘w’ with nonzero offset 1
[-Wfree-nonheap-object]
11 | free(w + 1);
| ^~~~~~~~~~~
```
gcc --version: gcc (Debian 13.2.0-2) 13.2.0
uname -a: Linux computer 6.4.0-3-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.4.11-1
(2023-08-17) x86_64 GNU/Linux
