https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671
--- Comment #45 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to rguent...@suse.de from comment #32)
> So you need to place may-alias at a point to make the following
> stmt safe:
>
> > c = *p;
>
> which means placing it on B, not only on the union (p is a B).
>
> Thus do
>
> struct B
> {
> int x;
> union U
> {
> int a;
> char b[sizeof (float)];
> } u;
> int y;
> } __attribute__((may_alias));
In the real code there is no B, there is just the union, and it is assigned
directly, so it's more like:
union function_buffer_members {
void* p;
void(*fp)();
};
union function_buffer {
function_buffer_members members;
char data[sizeof(function_buffer_members)];
};
struct function_base {
mutable function_buffer functor;
};
struct function : function_base {
void func(const function& f) {
this->functor = f.functor;
}
};
So it should only be necessary to put __attribute__((may_alias)) on union
function_buffer, right? That doesn't fix the problem though.
