[Bug c/81824] Warn for missing attributes with function aliases

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81824

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=81854

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The challenge here is that the alias target may not be in scope at the point of
the alias declaration, so while the test case in comment #0 could be detected
by enhancing the handle_alias_attribute function in c-family/c-attribs.c, one
where the declaration order is reversed as in the following could not be:

  void foo (void) __attribute__ ((nothrow, weak, alias ("__foo")));
  void __foo (void) { }

Bug 81854 suggests that there is a way to detect this in handle_alias_pairs()
in cgraphunit.c.