| Issue |
114772
|
| Summary |
Invalid optimization: clang makes invalid assumptions about malloc
|
| Labels |
|
| Assignees |
|
| Reporter |
bhaible
|
When optimizing, clang apparently assumes that a `malloc` invocation does not change `errno`. This assumption is wrong: on all platforms, `malloc` sets `errno` (usually to `ENOMEM`) when it returns NULL.
**How to reproduce:**
Save this as foo.c.
```
#include <stdlib.h> /* malloc */
#include <errno.h> /* errno */
#include <stdio.h> /* printf */
#include <stdint.h> /* SIZE_MAX */
int
main ()
{
errno = 0;
void *volatile p = malloc (SIZE_MAX / 10);
int err = errno;
printf ("errno=%d\n", err);
}
```
Then:
```
$ clang -O2 foo.c && ./a.out
errno=0
$ clang foo.c && ./a.out
errno=12
```
```
$ clang --version
clang version 19.1.0 (/home/runner/work/llvm-project/llvm-project/clang a4bf6cd7cfb1a1421ba92bca9d017b49936c55e4)
Target: x86_64-unknown-linux-gnu
Thread model: posix
```
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