From 94251ae99edaa911f4cb8056748dca0874ea268c Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 28 Jan 2025 21:53:49 +0000 Subject: Make fflush (NULL) flush input files (bug 32369) As discussed in bug 32369 and required by POSIX, the POSIX feature fflush (NULL) should flush input files, not just output files. The POSIX requirement is that "fflush() shall perform this flushing action on all streams for which the behavior is defined above", and the definition for input files is for "a stream open for reading with an underlying file description, if the file is not already at EOF, and the file is one capable of seeking". Implement this requirement in glibc. (The underlying flushing implementation is what deals with avoiding errors for seeking on an unseekable file.) Tested for x86_64. --- libio/genops.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'libio') diff --git a/libio/genops.c b/libio/genops.c index 2197bfe7a1..e4378ca48f 100644 --- a/libio/genops.c +++ b/libio/genops.c @@ -730,6 +730,13 @@ _IO_flush_all (void) ) && _IO_OVERFLOW (fp, EOF) == EOF) result = EOF; + if (_IO_fileno (fp) >= 0 + && ((fp->_mode <= 0 && fp->_IO_read_ptr < fp->_IO_read_end) + || (_IO_vtable_offset (fp) == 0 + && fp->_mode > 0 && (fp->_wide_data->_IO_read_ptr + < fp->_wide_data->_IO_read_end))) + && _IO_SYNC (fp) != 0) + result = EOF; _IO_funlockfile (fp); run_fp = NULL; -- cgit v1.2.3