[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #10 from Inbal Levi --- Actually, you're right about the origin being [dcl.align]p5 here too, though the test cases are different. Thanks.
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #9 from Jonathan Wakely --- Both bugs are violations of [dcl.align] p5 though. The bug is not that GCC doesn't follow [basic.align] p1 (it does) but that it allows alignas to weaken the alignment later. GCC should not allow alignas to weaken alignment on any declaration, whether a class declaration or variable declaration, and that's PR 65685. I've added a more complete testcase there, which includes alignas on object declarations.
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #8 from Inbal Levi --- See here: https://bugs.llvm.org/show_bug.cgi?id=45890
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #7 from Inbal Levi --- Not exactly. 94594 is talking about object's members impose their alignment on the object's type, whether this bug is talking about object type imposes its alignment on every object of that type (notice that in the example here, unlike the one on 94594, there's no alignment of the members). (this restriction is located at: [basic.align/1] [...] An object type imposes an alignment requirement on every object of that type; stricter alignment can be requested using the alignment specifier. as posted below in the comments, unfortunately, since I couldn't edit the bug) (Though, since posting that bug, I realized that though the restriction should hold, the querying part, which is alignof(object), should first be qualified in the standard. There's a paper: P2152 :) )
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 Jonathan Wakely changed: What|Removed |Added Resolution|--- |DUPLICATE Status|NEW |RESOLVED --- Comment #6 from Jonathan Wakely --- This seems like another dup of PR 65685 *** This bug has been marked as a duplicate of bug 65685 ***
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569
--- Comment #5 from Inbal Levi ---
Stumbled across another rule which might be relevant here is:
[basic.align/1]
[...] An object type imposes an alignment requirement on every object of that
type; stricter alignment can be requested using the alignment specifier
(9.12.2).
Inherited from the C standard, which results in an error for the following
code:
#include
typedef struct U U;
struct U {
} __attribute__((aligned (32)));
int main() {
_Alignas(16) U my_u; // alignas(obj) of a weaker alignment than the
type.
}
https://godbolt.org/z/tdEJgo
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 Jonathan Wakely changed: What|Removed |Added Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed||2020-04-14
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #4 from Richard Smith --- (In reply to Richard Biener from comment #3) > But isn't the alignas(32) also "appertaining to that entity"? No. The alignas(32) appertains to the struct. This is specified in [class]/2: "The optional attribute-specifier-seq appertains to the class".
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 Richard Biener changed: What|Removed |Added Keywords||accepts-invalid --- Comment #3 from Richard Biener --- But isn't the alignas(32) also "appertaining to that entity"?
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 --- Comment #2 from Inbal Levi --- Yes, you're probably right, got the wrong one. Thanks!
[Bug c++/94569] alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569 Richard Smith changed: What|Removed |Added CC||richard-gccbugzilla@metafoo ||.co.uk --- Comment #1 from Richard Smith --- I believe the particular rule that is violated by this example is [dcl.align]p5: "The combined effect of all alignment-specifiers in a declaration shall not specify an alignment that is less strict than the alignment that would be required for the entity being declared if all alignment-specifiers appertaining to that entity were omitted."
