There is a conformance test for OpenGL, and its my understanding that modern vendors use it. But I have no idea how comprehensive this test is.
It’s been a long-standing piece of advice that attributes should always be 4-byte aligned (though mainly for performance reasons. Even if the implementation didn’t break, I highly doubt it would have been fast). Unfortunately, it’s not a particularly publicized one.
I’d like to enforce conformity so it is more or less guaranteed to act and look the same on multiple platforms.
Yeah, that’s not a reasonable expectation at this point. The only way you can reasonably guarantee that your code will work the same across platforms is to test them yourself.
I mean yes, we should be able to expect this. But the reality of OpenGL implementations is what it is.