Re: How should vwprintf() work?

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Jul 21, 2004 at 11:55:59PM +0200, Petter Reinholdtsen wrote:
> 
> Based on this failure claim on
> <URL:http://www.dinkumware.com/conform_c.html>, I started looking on
> how vwprintf() work.
> 
>   - If L"" is passed as the format parameter to vwprintf a negative
>     value is returned, indicating an error occurred.
> 
> The vwprintf() function seem to terminate the program or block any
> printf() after it is called, or fail if a printf() was called first.
> Look at this example:
> 
>   % cat > x.c
>   #include <stdio.h>
>   #include <wchar.h>
>   #include <stdarg.h>
>   int main()
>   {
>     va_list args;
>     int i;
>   #if defined(TEST)
>     printf("started\n");
>   #endif /* TEST */
>     i = vwprintf(L"", args);
>     printf("retval: %d\n", i);
>     printf("ended\n");
>     return 0;
>   }
>   % cc -Wall x.c ; ./a.out
>   x.c: In function `main':
>   x.c:11: warning: implicit declaration of function `vwprintf'
>   % cc -DTEST -Wall x.c ; ./a.out
>   x.c: In function `main':
>   x.c:11: warning: implicit declaration of function `vwprintf'
>   started
>   retval: -1
>   ended
>   %
> 
> Is this a bug?  I'm testing on Debian/Unstable.

No, that's correct behaviour.
See e.g. ISO C99, 7.19.2:
Each stream has an orientation. After a stream is associated with an
external file, but before any operations are performed on it, the stream is
without orientation. Once a wide character input/output function has been
applied to a stream without orientation, the stream becomes a wide-oriented
stream . Similarly, once a byte input/output function has been applied to a
stream without orientation, the stream becomes a byte-oriented stream . Only
a call to the freopen function or the fwide function can otherwise alter the
orientation of a stream. (A successful call to freopen removes any
orientation.)

If you compile without -DTEST, vwprintf sets wide orientation on stdout
and so later printf on it will fail (but e.g.
wprintf(L"retval: %d\n", i); wprintf(L"ended\n");
would work).  If you compile with -DTEST, the first printf sets byte
orientation on stdout and thus vwprintf fails.

	Jakub