Re: Gnulib's freopen replacement and MinGW

On 05/05/2012 05:18 AM, Eli Zaretskii wrote:
> Diffutils 3.2 call xfreopen with its first argument NULL, expecting
> the underlying reopen to handle this.  However, the MS runtime does
> not implement the Posix semantics of such a call,

POSIX says that such a call is implementation-defined, so technically,
mingw DOES implement the POSIX semantics (by defining that it is
unsupported).  However, you are correct that it is annoying, and
something that gnulib could work around for easier coding.

> The following change fixes this:
> 
> 2012-05-05  Eli Zaretskii  <[email protected]>
> 
> 	* lib/freopen.c [_WIN32]: Include io.h and fcntl.h.
> 	(rpl_freopen) [_WIN32]: If the first argument is NULL, call
> 	_setmode to switch STREAM to either binary or text mode, as
> 	specified by MODE.
> 
> --- lib/freopen.c~0	2011-09-02 01:35:11.000000000 +0300
> +++ lib/freopen.c	2012-05-05 13:46:36.389000000 +0300
> @@ -37,11 +37,23 @@ orig_freopen (const char *filename, cons
>  
>  #include <string.h>
>  
> +#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
> +#include <io.h>
> +#include <fcntl.h>
> +#endif
> +
>  FILE *
>  rpl_freopen (const char *filename, const char *mode, FILE *stream)
>  {
>  #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
> -  if (filename != NULL && strcmp (filename, "/dev/null") == 0)
> +  if (filename == NULL)
> +    {
> +      if (strchr (mode, 'b'))
> +	return _setmode (_fileno (stream), _O_BINARY) == -1 ? NULL : stream;
> +      else
> +	return _setmode (_fileno (stream), _O_TEXT) == -1 ? NULL : stream;

Shouldn't we be doing some sanity checking, as in ensuring that a
read-only stream is not being reopened with 'w', or a write-only stream
is not being reopened with 'r'?  Also, shouldn't we be honoring 'w' vs.
'a' and adjusting the underlying fd's O_APPEND bit accordingly?

-- 
Eric Blake   [email protected]    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Public key at http://people.redhat.com/eblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQEcBAEBCAAGBQJPp8OQAAoJEKeha0olJ0NqEsEH/iDl9q8/7zJbz7kULqUFqwhg
6wEJaDoOV3kzE5PVanqKSUKQRioYSjVECXdpkoog86ZNReQhiEtYPHU0Mi0ZMqua
2kUfPuuDhbnlLqDBhCldTd+/iIl5WG3AoFqwXjVJZsSV5G5Mr7NOZqlwn0GQisXo
u57x01+0oiscItyNxmPtD7rFMSjDypxQ5ym+jley8LITkAJVPIsJbfHbOCNexrFl
EvZKhY7VjDdplgvK3+aOLn+3UYxs3g0jJkk66I0LH804XH34lC4K2lwfaeRG1Vzz
cCSvIVgGaWz4IB9pQSJ1COr+cPsVbUcasu3rBJWpGE61wBbMp10cOQHMGMw8QJw=
=TIY1
-----END PGP SIGNATURE-----