wchar_t printf() format warning

[Jonathan Roelofs]

On 3/18/15 3:29 PM, Joel Sherrill wrote:
> Hi
>
> I am returning to this issue. This appears to be similar to the
> intptr_t issue but with wchar_t. We get a printf() warning on
> targets where wchar_t is defined is defined as "long int" and
> not on targets where it is "int".  This appears to be because
> of a conflict in the definition of __WINT_TYPE__ and
> __WCHAR_TYPE__ by gcc.  I am open to suggestions on how
> to resolve this.
>
> $ sparc-rtems4.11-gcc -dM -E - </dev/null | grep WCHAR_TYPE
> #define __WCHAR_TYPE__ long int
> $ i386-rtems4.11-gcc -dM -E - </dev/null | grep WCHAR_TYPE
> #define __WCHAR_TYPE__ int
> $ sparc-rtems4.11-gcc -dM -E - </dev/null | grep WINT_TYPE
> #define __WINT_TYPE__ unsigned int
> $ i386-rtems4.11-gcc -dM -E - </dev/null | grep WINT_TYPE
> #define __WINT_TYPE__ unsigned int
>
>
> sparc generates this warning but i386 does not:
>
> $ sparc-rtems4.11-gcc -Wall -c wc.c
> wc.c: In function 'f':
> wc.c:10:3: warning: format '%lc' expects argument of type 'wint_t', but
> argument 4 has type 'wchar_t' [-Wformat=]
>     (void)printf("%*s%lc\n", pad, "", wc);
>     ^
> wc.c:10:3: warning: format '%lc' expects argument of type 'wint_t', but
> argument 4 has type 'wchar_t' [-Wformat=]
>
>
> This is the test case:
>
> =================
> #include <stdio.h>
> #include <wchar.h>
>
> void f(void)
> {
>
>    int pad = 10;
>    wchar_t wc = 'a';
>
>    (void)printf("%*s%lc\n", pad, "", wc);
§7.19.6.1 7:

"l (ell)
Specifies that a following d, i, o, u, x, or X conversion specifier 
applies to a long int or unsigned long int argument; that a following n 
conversion specifier applies to a pointer to a long int argument; that a 
following c conversion specifier applies to a wint_t argument; that a 
following s conversion specifier applies to a pointer to a wchar_t 
argument; or has no effect on a following a, A, e, E, f, F, g, or G 
conversion specifier."

You need a cast for the last argument: (wint_t)wc


Cheers,

Jon

> }
> =================
>

-- 
Jon Roelofs
jonathan@codesourcery.com
CodeSourcery / Mentor Embedded