On Fri, Feb 24, 2023 at 11:54:54AM +0000, Jonathan Wakely wrote:
> > The comment needs adjustment and don't we need
> > alignas (T) alignas (vec_prefix) ?
>
> Yes. If alignas(T) is less than the natural alignment then this will
> be an error. We want it to be the larger of the two alignments, so we
> need to specify both.
Seems g++ doesn't diagnose this but clang++ does:
struct S { int a; };
alignas (char) alignas (S) S s;
alignas (char) S t;
$ g++ -S -o /tmp/1.s /tmp/1.C -pedantic-errors
$ clang++ -S -o /tmp/1.s /tmp/1.C -pedantic-errors
/tmp/1.C:3:1: error: requested alignment is less than minimum alignment of 4
for type 'S'
alignas (char) S t;
^
1 error generated.
Jakub
