[Bug c/54486] New: Spurious printf format warning mentions nonexistent type 'sizetype'

["Keith.S.Thompson at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54486

             Bug #: 54486
           Summary: Spurious printf format warning mentions nonexistent
                    type 'sizetype'
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: Keith.S.Thompson@gmail.com


printf's "%zu" format expects an argument of type size_t.  In the sample
program, the corresponding argument is of type size_t in all the printf calls
(the first because strspn() is defined to return a size_t result, and the
second because of the explicit cast, and similarly for the others).

For a call to strlen() or to a user-defined function func(), gcc rightly does
not complain.

For a call to strspn(), even with an explicit cast, gcc incorrectly complains
that the arguments is of type ‘sizetype’ -- which, as far as I can tell,
doesn't exist.  (If I try to add a variable definition of type ‘sizetype’, I
get "error: unknown type name ‘sizetype’", and I can find no reference to
‘sizetype’ in any of my system's headers.)

I see nothing unusual in the declaration of strspn() in /usr/include/string.h.

$ uname -a 
Linux kvetch 3.2.0-29-generic-pae #46-Ubuntu SMP Fri Jul 27 17:25:43 UTC 2012
i686 i686 i386 GNU/Linux
$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.10
DISTRIB_CODENAME=quantal
DISTRIB_DESCRIPTION="Ubuntu quantal (development branch)"
$ gcc --version
gcc (Ubuntu/Linaro 4.7.0-7ubuntu3) 4.7.0
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.

$ cat c.c
#include <string.h>
#include <stdio.h>

extern size_t func(void);

int main(void) {
    printf("%zu\n",         strspn("abc", "abcdefg")); /* line 7 */
    printf("%zu\n", (size_t)strspn("abc", "abcdefg")); /* line 8 */
    printf("%zu\n",         strlen("foo"));
    printf("%zu\n", (size_t)strlen("foo"));
    printf("%zu\n",         func());
    printf("%zu\n", (size_t)func());
    return 0;               
}                           
$ gcc -c -std=c99 -pedantic c.c
c.c: In function ‘main’:    
c.c:7:5: warning: format ‘%zu’ expects argument of type ‘size_t’, but argument
2 has type ‘sizetype’ [-Wformat]
c.c:8:5: warning: format ‘%zu’ expects argument of type ‘size_t’, but argument
2 has type ‘sizetype’ [-Wformat]
$