| Issue |
169494
|
| Summary |
[clang] _Pragma() in macro interfering with macro return type
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
alexveden
|
I have a macro that started behaving differently after upgrading to clang-22, it worked previously in CI for:
- GCC - 10, 11, 12, 13, 14, 15
- Clang - 13, 14, 15, 16, 17, 18, 19, 20, 21
Minimal example:
```c
#include <stdio.h>
#include <stdint.h>
size_t
_cexds__arr_len(const void* arr)
{
// This function is a mock for returning length of dynamic arrays
return (arr) ? 6969 : 0;
}
# define arr$len(arr) \
({ \
_Pragma("GCC diagnostic push"); \
/* NOTE: temporary disable syntax error to support both static array length and \
* arr$(T) */ \
_Pragma("GCC diagnostic ignored \"-Wsizeof-pointer-div\""); \
/* NOLINTBEGIN */ \
__builtin_types_compatible_p( \
typeof(arr), \
typeof(&(arr)[0]) \
) /* check if array or ptr */ \
? _cexds__arr_len(arr) /* some pointer or arr$ */ \
: ( \
sizeof(arr) / sizeof((arr)[0]) /* static array[] */ \
); \
/* NOLINTEND */ \
_Pragma("GCC diagnostic pop"); \
})
int main(int argc, char** argv) {
char* a[] = {"a", "b"};
printf("a is static, arr$len=%zu\n", arr$len(a));
char* a1 = (void*)0xbadcaffe;
printf("a is kinda dynamic, arr$len=%zu\n", arr$len(a1));
return 0;
}
```
Returns:
```
~/code/cex/clang22issues ➜ /home/av/code/emsdk/upstream/bin/clang -ferror-limit=100000 ./clang_test.c
./clang_test.c:32:42: error: argument type 'void' is incomplete
32 | printf("a is static, arr$len=%zu\n", arr$len(a));
| ^
./clang_test.c:12:9: note: expanded from macro 'arr$len'
12 | ({ \
| ^
./clang_test.c:35:49: error: argument type 'void' is incomplete
35 | printf("a is kinda dynamic, arr$len=%zu\n", arr$len(a1));
| ^
./clang_test.c:12:9: note: expanded from macro 'arr$len'
12 | ({ \
| ^
2 errors generated.
```
If you remove `_Pragma("GCC diagnostic pop"); ` in `arr$len()` macro, it compiles and runs properly.
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