151 lines
4.7 KiB
Diff
151 lines
4.7 KiB
Diff
commit 94251ae99edaa911f4cb8056748dca0874ea268c
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Author: Joseph Myers <josmyers@redhat.com>
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Date: Tue Jan 28 21:53:49 2025 +0000
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Make fflush (NULL) flush input files (bug 32369)
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As discussed in bug 32369 and required by POSIX, the POSIX feature
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fflush (NULL) should flush input files, not just output files. The
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POSIX requirement is that "fflush() shall perform this flushing action
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on all streams for which the behavior is defined above", and the
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definition for input files is for "a stream open for reading with an
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underlying file description, if the file is not already at EOF, and
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the file is one capable of seeking".
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Implement this requirement in glibc. (The underlying flushing
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implementation is what deals with avoiding errors for seeking on an
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unseekable file.)
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Tested for x86_64.
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diff --git a/libio/genops.c b/libio/genops.c
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index cf6985938255e70d..560cbdd587ad2240 100644
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--- a/libio/genops.c
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+++ b/libio/genops.c
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@@ -706,6 +706,13 @@ _IO_flush_all (void)
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)
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&& _IO_OVERFLOW (fp, EOF) == EOF)
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result = EOF;
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+ if (_IO_fileno (fp) >= 0
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+ && ((fp->_mode <= 0 && fp->_IO_read_ptr < fp->_IO_read_end)
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+ || (_IO_vtable_offset (fp) == 0
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+ && fp->_mode > 0 && (fp->_wide_data->_IO_read_ptr
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+ < fp->_wide_data->_IO_read_end)))
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+ && _IO_SYNC (fp) != 0)
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+ result = EOF;
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_IO_funlockfile (fp);
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run_fp = NULL;
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diff --git a/stdio-common/Makefile b/stdio-common/Makefile
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index ed358394c90f2319..0476c3777d7d21c4 100644
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--- a/stdio-common/Makefile
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+++ b/stdio-common/Makefile
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@@ -222,6 +222,7 @@ tests := \
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tst-fdopen \
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tst-fdopen2 \
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tst-ferror \
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+ tst-fflush-all-input \
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tst-fgets \
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tst-fgets2 \
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tst-fileno \
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diff --git a/stdio-common/tst-fflush-all-input.c b/stdio-common/tst-fflush-all-input.c
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new file mode 100644
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index 0000000000000000..8e3fca3a087a1699
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--- /dev/null
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+++ b/stdio-common/tst-fflush-all-input.c
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@@ -0,0 +1,94 @@
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+/* Test fflush (NULL) flushes input files (bug 32369).
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+ Copyright (C) 2025 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <stdio.h>
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+#include <stdlib.h>
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+#include <unistd.h>
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+#include <wchar.h>
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+
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+#include <support/check.h>
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+#include <support/xstdio.h>
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+#include <support/xunistd.h>
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+
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+int
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+do_test (void)
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+{
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+ FILE *temp = tmpfile ();
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+ TEST_VERIFY_EXIT (temp != NULL);
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+ fprintf (temp, "abc");
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+ TEST_COMPARE (fflush (temp), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_SET), 0);
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+ TEST_COMPARE (fgetc (temp), 'a');
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+ TEST_COMPARE (fflush (NULL), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_CUR), 1);
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+ xfclose (temp);
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+
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+ /* Likewise, but in wide mode. */
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+ temp = tmpfile ();
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+ TEST_VERIFY_EXIT (temp != NULL);
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+ fwprintf (temp, L"abc");
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+ TEST_COMPARE (fflush (temp), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_SET), 0);
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+ TEST_COMPARE (fgetwc (temp), L'a');
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+ TEST_COMPARE (fflush (NULL), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_CUR), 1);
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+ xfclose (temp);
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+
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+ /* Similar tests, but with the flush implicitly occurring on exit
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+ (in a forked subprocess). */
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+
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+ temp = tmpfile ();
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+ TEST_VERIFY_EXIT (temp != NULL);
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+ pid_t pid = xfork ();
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+ if (pid == 0)
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+ {
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+ fprintf (temp, "abc");
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+ TEST_COMPARE (fflush (temp), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_SET), 0);
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+ TEST_COMPARE (fgetc (temp), 'a');
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+ exit (EXIT_SUCCESS);
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+ }
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+ else
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+ {
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+ TEST_COMPARE (xwaitpid (pid, NULL, 0), pid);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_CUR), 1);
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+ xfclose (temp);
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+ }
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+
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+ temp = tmpfile ();
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+ TEST_VERIFY_EXIT (temp != NULL);
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+ pid = xfork ();
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+ if (pid == 0)
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+ {
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+ fwprintf (temp, L"abc");
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+ TEST_COMPARE (fflush (temp), 0);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_SET), 0);
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+ TEST_COMPARE (fgetwc (temp), L'a');
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+ exit (EXIT_SUCCESS);
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+ }
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+ else
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+ {
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+ TEST_COMPARE (xwaitpid (pid, NULL, 0), pid);
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+ TEST_COMPARE (lseek (fileno (temp), 0, SEEK_CUR), 1);
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+ xfclose (temp);
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+ }
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+
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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