[Bug c/58217] New: warning when assigning a function pointer field in a structure having the may_alias attribute

[zer0@droids-corp.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58217

            Bug ID: 58217
           Summary: warning when assigning a function pointer field in a
                    structure having the may_alias attribute
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zer0@droids-corp.org
              Host: x86_64
            Target: x86_64

Hello,

When compiling the attached code, I get the following error:

$ gcc -Wall -Wextra foo.c
foo.c: In function ‘main’:
foo.c:16:16: warning: assignment from incompatible pointer type [enabled by
default]

If I remove the "__attribute__((may_alias))", it compiles. A workaround it
to cast the cb function pointer in (void *) before doing the affectation. In my
opinion, this warning is not expected here. Sorry if I missed something.

I also tried:

$ gcc -Wall -Wextra -fno-strict-aliasing -fwrapv foo.c
foo.c: In function ‘main’:
foo.c:16:16: warning: assignment from incompatible pointer type [enabled by
default]


$ gcc --version
gcc (Debian 4.7.3-4) 4.7.3
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I can reproduce the problem on several gcc versions 4.4, 4.5, 4.6 at least.