Sorry for responding again, but I was really curious about that "inline" struct type attribute format so I figured I would do some tests. It looks like it actually doesn't do anything! And the warnings are definitely wrong in at least one case. To get straight to the point, some code:
#include
#include
struct s {
char b;
int k;
};
int main()
{
printf("offsetof packed k: %zd\n", offsetof(struct __attribute__((packed)) s, k));
printf("offsetof regular k: %zd\n", offsetof(struct s, k));
printf("alignof inline: %zd\n", __alignof__(struct __attribute__((aligned(32))) s));
printf("alignof before: %zd\n", __alignof__(__attribute__((aligned(32))) struct s));
printf("alignof regular: %zd\n", __alignof__(struct s));
return 0;
}
The outputs of this program (Just the numbers) are 4, 4, 4, 32, 4. If the 'inline' attributes were actually respected, the results would be 2, 4, 32, 32, 4. Meaning, the attributes in test's 1 and 3 are completely ignored but do not produce warnings. Also interesting, test 4 actually produces a warning about the `aligned` attribute being ignored even though it actually respects it (as it should). I think this is a just weird issue edge-case with the `alignof` operator specific to `gcc`, since `alignof` takes a 'type' as input, but it's definitely a bug. If you declare a variable with that type there is no warning.
Besides the warnings this doesn't surprise me too much, AFAIK it is not legal to put anything between the `struct` and the structure name in usages of a `struct` type. But from the response gotten over at the `gcc` Bugzilla I would wager the 'inline' versions are in the uncharted waters of "Nobody really knows what that should do anymore, don't do that". Reading the `gcc` bug report again, it seems the last response does actually indicate the error I'm pointing out above, where the attribute is silently ignored, I missed that when I skimmed it the first time.
With that said, the fix EMACS implemented was the same as just removing the attribute completely. If the EMACS code really does need that alignment forced for one of its architectures, it should probably take a look at that fix again and apply the `aligned` attribute on the `struct thread_state` for the architecture(s) that need the 8-byte alignment (If they actually exist), and then remove the attribute completely from the variable declaration.