https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94338
--- Comment #11 from huaixin chang <huaixin....@alibaba-inc.com> ---
(In reply to huaixin chang from comment #10)
> (In reply to Richard Biener from comment #9)
> > Btw,
> >
> > struct X {
> > long a __attribute__((__aligned__(128)));
> > long b __attribute__((__aligned__(128)));
> > };
> > struct X A __attribute__((__aligned__(4)));
> >
> > is not diagnosed (this is what your testcase is, decomposed).
> >
> > I can't reproduce the diagnostics you describe in comment#5
>
> I am sorry that I made a mistake in testing typedef described in comment#5.
>
> I spelled __aligned__ into __aligned, got warned "warning: '__aligned'
> attribute directive ignored [-Wattributes]", and thought I got diagnosed
> because of reduction in alignment. As a result, neither type foo nor object
> A is reduced in alignment with the code describe in comment#5.
>
> I have tested typedef again, and found that it behaves the same with using
> struct under gcc 9.2.1. That is to say, no matter I define A using struct
> like:
>
> -----------------------------------
> struct X {
> long a __attribute__((__aligned__(128)));
> long b __attribute__((__aligned__(128)));
> };
> struct X A __attribute__((__aligned__(4)));
>
> or use typedef and reduce the alignment of type foo like:
> -----------------------------------
> typedef struct {
> long a __attribute__((__aligned__(128)));
> long b __attribute__((__aligned__(128)));
> } foo __attribute__((__aligned(4)));
Another spelling mistake. It should be:
} foo __attribute__((__aligned__(4)));
>
> foo A;
>
> or use typedef and reduce the alignment of A like:
> -----------------------------------
> typedef struct {
> long a __attribute__((__aligned__(128)));
> long b __attribute__((__aligned__(128)));
> } foo;
>
> foo A __attribute__((__aligned__(4)));
>
> I got no warn on compiling and it behaves like this.
> -----------------------------------
> address of A 0x42003c
> alignof A 4
> address of A.a 0x42003c
> alignof A.a 128
> address of A.b 0x4200bc
> alignof A.b 128
> address of B 0x420038
