| Issue |
143284
|
| Summary |
unnecessary constraint enforcement in arguments to __builtin_types_compatible_p
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
alejandro-colomar
|
Here's a small reproducer:
```c
alx@devuan:~/tmp$ cat cnt.c
#include <stdlib.h>
#include <assert.h>
#define must_be(e) \
( \
0 * (int) sizeof( \
struct { \
static_assert(e, ""); \
int ISO_C_forbids_a_struct_with_no_members_; \
} \
) \
)
#define is_same_type(a, b) \
( \
__builtin_types_compatible_p(a, b) \
)
#define is_same_typeof(a, b) \
( \
is_same_type(typeof(a), typeof(b)) \
)
#define is_array(a) \
( \
!is_same_typeof(a, &(a)[0]) \
)
int
main(void)
{
return must_be(is_array(((int []) {rand(), rand()})));
}
```
```c
alx@devuan:~/tmp$ gcc -Wall -Wextra -S cnt.c
alx@devuan:~/tmp$
```
```c
alx@devuan:~/tmp$ clang -Wall -Wextra -S cnt.c
cnt.c:34:37: error: initializer element is not a compile-time constant
34 | return must_be(is_array(((int []) {rand(), rand()})));
| ^~~~~~
cnt.c:27:25: note: expanded from macro 'is_array'
27 | !is_same_typeof(a, &(a)[0]) \
| ^
cnt.c:22:29: note: expanded from macro 'is_same_typeof'
22 | is_same_type(typeof(a), typeof(b)) \
| ^
cnt.c:17:38: note: expanded from macro 'is_same_type'
17 | __builtin_types_compatible_p(a, b) \
| ^
cnt.c:9:39: note: expanded from macro 'must_be'
9 | static_assert(e, ""); \
| ^
1 error generated.
```
Please include the following in an eventual fix:
```
Reported-by: "Basil L. Contovounesios" <ba...@contovou.net>
Reported-by: Alejandro Colomar <a...@kernel.org>
```
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