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author | Bruno Haible <bruno@clisp.org> | 2007-04-27 10:56:51 +0000 |
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committer | Bruno Haible <bruno@clisp.org> | 2007-04-27 10:56:51 +0000 |
commit | 8a076be4c531a3d68ab4a3b9448cbdbe7f498193 (patch) | |
tree | a8c22480dca2d679b1ceb9a8acc63a445dde6516 /lib/fflush.c | |
parent | b257336e8496769a21a80072057a78d8b04fae20 (diff) | |
download | gnulib-8a076be4c531a3d68ab4a3b9448cbdbe7f498193.tar.gz |
More comments.
Diffstat (limited to 'lib/fflush.c')
-rwxr-xr-x | lib/fflush.c | 27 |
1 files changed, 22 insertions, 5 deletions
diff --git a/lib/fflush.c b/lib/fflush.c index 9361c09f3f..2d814957fa 100755 --- a/lib/fflush.c +++ b/lib/fflush.c @@ -38,11 +38,24 @@ rpl_fflush (FILE *stream) int result; off_t pos; - /* When stream is NULL, POSIX only requires flushing of output - streams. C89 guarantees behavior of output streams, and fflush - should be safe on read-write streams that are not currently - reading. */ - if (! stream || ! freading (stream)) + /* When stream is NULL, POSIX and C99 only require flushing of "output + streams and update streams in which the most recent operation was not + input", and all implementations do this. + + When stream is "an output stream or an update stream in which the most + recent operation was not input", POSIX and C99 requires that fflush + writes out any buffered data, and all implementations do this. + + When stream is, however, an input stream or an update stream in which + the most recent operation was input, POSIX and C99 specify nothing. + mingw, in particular, drops the input buffer, leaving the file descriptor + positioned at the end of the input buffer. I.e. ftell (stream) is lost. + We don't want to call the implementation's fflush in this case. + + We test ! freading (stream) here, rather than fwriting (stream), because + what we need to know is whether the stream holds a "read buffer", and on + mingw this is indicated by _IOREAD, regardless of _IOWRT. */ + if (stream == NULL || ! freading (stream)) return fflush (stream); /* POSIX does not specify fflush behavior for non-seekable input @@ -60,12 +73,16 @@ rpl_fflush (FILE *stream) result = fpurge (stream); if (result != 0) return result; + pos = lseek (fileno (stream), pos, SEEK_SET); if (pos == -1) return EOF; + /* After a successful lseek, update the file descriptor's position cache + in the stream. */ #if defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */ stream->_offset = pos; stream->_flags |= __SOFF; #endif + return 0; } |