https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77388
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
This happens on x86_64 as well and is because you invoke undefined behavior
when extending the lifetime of A::c across the lifetime of the object
it refers to. s->c is an rvalue here because it's type isn't compatible
due to the mismatched alignment and thus a temporary of correct alignment
is build and the address of that is passed to A::A.
I suppose the FE could emit a warning here.
Oh, and the .optimized you see is because the FE emits a CLOBBER to explicitely
end the lifetime of said temporary:
A B::foo() (struct B * const this)
{
const short int & SR.1;
const short int D.2330;
struct A D.2331;
struct A D.2342;
struct test_struct * _1;
short int _2;
<bb 2>:
_1 = this_4(D)->s;
_2 = _1->c;
D.2330 = _2;
MEM[(struct A *)&D.2342] = &D.2330;
D.2330 ={v} {CLOBBER};
return D.2342;
thus we can DSE the store to D.2330.
