Bug#425623: gcc-4.1: Option to warn on printf of ptrdiff_t without t size modifier

[Josh Triplett <josh@freedesktop.org>]

Package: gcc-4.1
Version: 4.1.2-7
Severity: wishlist

This code:

#include <stdio.h>
int main(int argc, char *argv[])
{
	void *a, *b;
	printf("%d\n", a - b);
	return 0;
}

will generate this warning on a 64-bit platform:

temp.c:5: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long int’

because a - b has type ptrdiff_t and sizeof(ptrdiff_t) == 8 on a 64-bit
platform.  However, on a 32-bit platform the code will generate no warning.  I
believe it should generate a warning like this on all platforms, if not by
default then with an appropriate option:

temp.c:5: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘ptrdiff_t’

In C99, such code can use %td; the t size modifier corresponds to the
ptrdiff_t type.  If the code does not want to count on c99, it could cast the
difference to a long and use %ld.

- Josh Triplett

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: i386 (i686)

Kernel: Linux 2.6.22-rc1 (PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gcc-4.1 depends on:
ii  binutils               2.17cvs20070426-6 The GNU assembler, linker and bina
ii  cpp-4.1                4.1.2-7           The GNU C preprocessor
ii  gcc-4.1-base           4.1.2-7           The GNU Compiler Collection (base 
ii  libc6                  2.5-8             GNU C Library: Shared libraries
ii  libgcc1                1:4.2-20070516-1  GCC support library

Versions of packages gcc-4.1 recommends:
ii  libc6-dev                     2.5-8      GNU C Library: Development Librari
ii  libmudflap0-dev               4.1.2-7    GCC mudflap support libraries (dev

-- no debconf information