Eric Blake wrote:
> > You said that you got an fflush failure on mingw. Could you please
> > show a test program that failed before?
>
> The m4 test suite detected failures on mingw due to this code that got
> invoked prior to the syscmd macro, in an attempt to follow the POSIX rule
> that for seekable streams, child processes should see the stream at the
> next character left unprocessed by the parent:
>
> if (lseek (STDIN_FILENO, 0, SEEK_CUR) >= 0
> && fflush (stdin) == 0)
> {
> fseeko (stdin, 0, SEEK_CUR);
> }
>
> The failures in the m4 testsuite were due to lost data since the fflush
> discarded what was on the pipe, even though the fflush should never have
> been reached.
Thanks for explaining. I thought you were talking about the lseek call
inside fflush, not about an lseek call before it.
Since loss of data is a severe condition, I'm adding a note about it:
2007-05-28 Bruno Haible <[EMAIL PROTECTED]>
* lib/stdio_.h (fflush): More comments.
--- lib/stdio_.h 24 May 2007 16:59:21 -0000 1.27
+++ lib/stdio_.h 28 May 2007 13:52:52 -0000
@@ -270,7 +270,11 @@
# if @REPLACE_FFLUSH@
# define fflush rpl_fflush
/* Flush all pending data on STREAM according to POSIX rules. Both
- output and seekable input streams are supported. */
+ output and seekable input streams are supported.
+ Note! LOSS OF DATA can occur if fflush is applied on an input stream
+ that is _not_seekable_ or on an update stream that is _not_seekable_
+ and in which the most recent operation was input. Seekability can
+ be tested with lseek(fileno(fp),0,SEEK_CUR). */
extern int fflush (FILE *gl_stream);
# endif
#elif defined GNULIB_POSIXCHECK
