[Bug c++/69843] C++: Inconsistent treatment of may_alias attribute and forward declarations

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69843

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For
struct sockaddr;
struct sockaddr *foo (void);

struct __attribute__ ((may_alias)) sockaddr
{
};

struct sockaddr *
foo (void)
{
  return (struct sockaddr *) 0;
}
we reject it in C and ICE in C++:
internal compiler error: canonical types differ for identical types sockaddr*
and sockaddr*