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Re: [PATCH] libio: Flush stream at freopen (BZ#21037)
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Tue, 8 Aug 2017 10:52:49 -0300
- Subject: Re: [PATCH] libio: Flush stream at freopen (BZ#21037)
- Authentication-results: sourceware.org; auth=none
- References: <1499977587-28794-1-git-send-email-adhemerval.zanella@linaro.org>
Ping.
On 13/07/2017 17:26, Adhemerval Zanella wrote:
> As POSIX states [1] a freopen call should first flush the stream as
> if by a call fflush. C99 (n1256) and C11 (n1570) only states the
> function should first close any file associated with the specific
> stream. Although current implementation only follow C specification,
> current BSD and other libc implementation (musl) are in sync with
> POSIX and fflush the stream.
>
> This patch change freopen{64} to fflush the stream before actually
> reopening it (or returning if the stream does not support reopen).
> It also changes the Linux implementation to avoid a dynamic
> allocation on 'fd_to_filename'.
>
> Checked on x86_64-linux-gnu.
>
> From Florian's comment, this is intended for 2.27. This patch should
> be applied on top on 'libio: Fix open_memstream fflush (NULL) (BZ#21735)' [2].
>
> [BZ #21037]
> * libio/freopen.c (freopen): Sync stream before reopen and adjust to
> new fd_to_filename interface.
> * libio/freopen64.c (freopen64): Likewise.
> * sysdeps/generic/fd_to_filename.h (fd_to_filename): Change signature.
> * sysdeps/unix/sysv/linux/fd_to_filename.h (fd_to_filename): Likewise
> and remove internal dynamic allocation.
> * libio/Makefile (tests): Add tst-memstream5 and tst-wmemstream5.
> * libio/tst-memstream.h (FPUTS): New macro.
> * libio/tst-memstream4.c: New file.
> * libio/tst-wmemstream4.c: Likewise.
>
> [1] http://pubs.opengroup.org/onlinepubs/9699919799/
> [2] https://sourceware.org/ml/libc-alpha/2017-07/msg00548.html
> ---
> ChangeLog | 14 ++++++++
> libio/Makefile | 3 +-
> libio/freopen.c | 33 ++++++++++-------
> libio/freopen64.c | 30 ++++++++++------
> libio/tst-memstream.h | 2 ++
> libio/tst-memstream5.c | 62 ++++++++++++++++++++++++++++++++
> libio/tst-wmemstream5.c | 20 +++++++++++
> sysdeps/generic/fd_to_filename.h | 6 ++--
> sysdeps/unix/sysv/linux/fd_to_filename.h | 31 +++++-----------
> 9 files changed, 151 insertions(+), 50 deletions(-)
> create mode 100644 libio/tst-memstream5.c
> create mode 100644 libio/tst-wmemstream5.c
>
> diff --git a/libio/Makefile b/libio/Makefile
> index 6ee809a..8adf2d8 100644
> --- a/libio/Makefile
> +++ b/libio/Makefile
> @@ -58,8 +58,9 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc \
> tst-mmap2-eofsync tst-mmap-offend bug-fopena+ bug-wfflush \
> bug-ungetc2 bug-ftell bug-ungetc3 bug-ungetc4 tst-fopenloc2 \
> tst-memstream1 tst-memstream2 tst-memstream3 tst-memstream4 \
> + tst-memstream5 \
> tst-wmemstream1 tst-wmemstream2 tst-wmemstream3 tst-wmemstream4 \
> - bug-memstream1 bug-wmemstream1 \
> + tst-wmemstream5 bug-memstream1 bug-wmemstream1 \
> tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos tst-fseek \
> tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \
> tst-ftell-append tst-fputws
> diff --git a/libio/freopen.c b/libio/freopen.c
> index 980523a..505e77d 100644
> --- a/libio/freopen.c
> +++ b/libio/freopen.c
> @@ -24,28 +24,38 @@
> This exception applies to code released by its copyright holders
> in files containing the exception. */
>
> -#include "libioP.h"
> -#include "stdio.h"
> +#include <stdio.h>
> #include <fcntl.h>
> #include <stdlib.h>
> #include <unistd.h>
>
> -#include <shlib-compat.h>
> +#include <libioP.h>
> #include <fd_to_filename.h>
> -
> -#include <kernel-features.h>
> +#include <shlib-compat.h>
>
> FILE *
> freopen (const char *filename, const char *mode, FILE *fp)
> {
> - FILE *result;
> + FILE *result = NULL;
> + char fdfilename[30];
> +
> CHECK_FILE (fp, NULL);
> - if (!(fp->_flags & _IO_IS_FILEBUF))
> - return NULL;
> +
> _IO_acquire_lock (fp);
> + /* First flush the stream (failure should be ignored). */
> + _IO_SYNC (fp);
> +
> + if (!(fp->_flags & _IO_IS_FILEBUF))
> + goto end;
> +
> int fd = _IO_fileno (fp);
> - const char *gfilename = (filename == NULL && fd >= 0
> - ? fd_to_filename (fd) : filename);
> + const char *gfilename;
> + if (filename == NULL && fd >= 0)
> + gfilename = fd_to_filename (fd, fdfilename, sizeof fdfilename)
> + ? fdfilename : NULL;
> + else
> + gfilename = filename;
> +
> fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
> #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
> if (&_IO_stdin_used == NULL)
> @@ -101,9 +111,6 @@ freopen (const char *filename, const char *mode, FILE *fp)
> __close (fd);
>
> end:
> - if (filename == NULL)
> - free ((char *) gfilename);
> -
> _IO_release_lock (fp);
> return result;
> }
> diff --git a/libio/freopen64.c b/libio/freopen64.c
> index 1e56de6..28203c9 100644
> --- a/libio/freopen64.c
> +++ b/libio/freopen64.c
> @@ -24,27 +24,37 @@
> This exception applies to code released by its copyright holders
> in files containing the exception. */
>
> -#include "libioP.h"
> -#include "stdio.h"
> +#include <stdio.h>
> #include <fcntl.h>
> #include <stdlib.h>
> #include <unistd.h>
>
> +#include <libioP.h>
> #include <fd_to_filename.h>
>
> -#include <kernel-features.h>
> -
> FILE *
> freopen64 (const char *filename, const char *mode, FILE *fp)
> {
> - FILE *result;
> + FILE *result = NULL;
> + char fdfilename[30];
> +
> CHECK_FILE (fp, NULL);
> - if (!(fp->_flags & _IO_IS_FILEBUF))
> - return NULL;
> +
> _IO_acquire_lock (fp);
> + /* First flush the stream (failure should be ignored). */
> + _IO_SYNC (fp);
> +
> + if (!(fp->_flags & _IO_IS_FILEBUF))
> + goto end;
> +
> int fd = _IO_fileno (fp);
> - const char *gfilename = (filename == NULL && fd >= 0
> - ? fd_to_filename (fd) : filename);
> + const char *gfilename;
> + if (filename == NULL && fd >= 0)
> + gfilename = fd_to_filename (fd, fdfilename, sizeof fdfilename)
> + ? fdfilename : NULL;
> + else
> + gfilename = filename;
> +
> fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
> _IO_file_close_it (fp);
> _IO_JUMPS_FILE_plus (fp) = &_IO_file_jumps;
> @@ -84,8 +94,6 @@ freopen64 (const char *filename, const char *mode, FILE *fp)
> __close (fd);
>
> end:
> - if (filename == NULL)
> - free ((char *) gfilename);
> _IO_release_lock (fp);
> return result;
> }
> diff --git a/libio/tst-memstream.h b/libio/tst-memstream.h
> index ffc2a65..86ea0d7 100644
> --- a/libio/tst-memstream.h
> +++ b/libio/tst-memstream.h
> @@ -49,6 +49,7 @@ fwwrite (const void *ptr, size_t size, size_t nmemb, FILE *arq)
> # define PRINTF wprintf
> # define FWRITE fwwrite
> # define FPUTC fputwc
> +# define FPUTS fputws
> # define STRCMP wcscmp
> # define STRLEN wcslen
> #else
> @@ -58,6 +59,7 @@ fwwrite (const void *ptr, size_t size, size_t nmemb, FILE *arq)
> # define PRINTF printf
> # define FWRITE fwrite
> # define FPUTC fputc
> +# define FPUTS fputs
> # define STRCMP strcmp
> # define STRLEN strlen
> #endif
> diff --git a/libio/tst-memstream5.c b/libio/tst-memstream5.c
> new file mode 100644
> index 0000000..7c1f37c
> --- /dev/null
> +++ b/libio/tst-memstream5.c
> @@ -0,0 +1,62 @@
> +/* Test for open_memstream BZ #21037.
> + Copyright (C) 2017 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#include "tst-memstream.h"
> +
> +static void
> +mcheck_abort (enum mcheck_status ev)
> +{
> + printf ("mecheck failed with status %d\n", (int) ev);
> + exit (1);
> +}
> +
> +static int
> +do_test (void)
> +{
> + mcheck_pedantic (mcheck_abort);
> +
> + /* Check if freopen proper fflush the stream. */
> + {
> + CHAR_T old[] = W("old");
> + CHAR_T *buf = old;
> + size_t size;
> +
> + FILE *fp = OPEN_MEMSTREAM (&buf, &size);
> + TEST_VERIFY_EXIT (fp != NULL);
> +
> + FPUTS (W("new"), fp);
> + /* The stream buffer pointer should be updated with only a fflush or
> + fclose. */
> + TEST_VERIFY (STRCMP (buf, old) == 0);
> +
> + /* The old stream should be fflush the stream, even for an invalid
> + streams. */
> + FILE *nfp = freopen ("invalid-file", "r", fp);
> + TEST_VERIFY (nfp == NULL);
> +
> + TEST_VERIFY (STRCMP (buf, W("new")) == 0);
> +
> + TEST_VERIFY (fclose (fp) == 0);
> +
> + free (buf);
> + }
> +
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/libio/tst-wmemstream5.c b/libio/tst-wmemstream5.c
> new file mode 100644
> index 0000000..4e87289
> --- /dev/null
> +++ b/libio/tst-wmemstream5.c
> @@ -0,0 +1,20 @@
> +/* Test for open_wmemstream BZ #21037.
> + Copyright (C) 2017 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#define TEST_WCHAR
> +#include <libio/tst-memstream5.c>
> diff --git a/sysdeps/generic/fd_to_filename.h b/sysdeps/generic/fd_to_filename.h
> index fe15f5d..db594f2 100644
> --- a/sysdeps/generic/fd_to_filename.h
> +++ b/sysdeps/generic/fd_to_filename.h
> @@ -18,8 +18,8 @@
>
> /* In general there is no generic way to query filename for an open
> file descriptor. */
> -static inline const char *
> -fd_to_filename (int fd)
> +static inline bool
> +fd_to_filename (int fd, char *buf, size_t len)
> {
> - return NULL;
> + return false;
> }
> diff --git a/sysdeps/unix/sysv/linux/fd_to_filename.h b/sysdeps/unix/sysv/linux/fd_to_filename.h
> index 414a30f..6cd0bdd 100644
> --- a/sysdeps/unix/sysv/linux/fd_to_filename.h
> +++ b/sysdeps/unix/sysv/linux/fd_to_filename.h
> @@ -16,30 +16,17 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> -#include <stdlib.h>
> -#include <string.h>
> +#include <stdio.h>
> #include <sys/stat.h>
> -#include <_itoa.h>
>
> -static inline const char *
> -fd_to_filename (int fd)
> +static inline bool
> +fd_to_filename (int fd, char *buf, size_t len)
> {
> - char *ret = malloc (30);
> + __snprintf (buf, len, "/proc/self/fd/%d", fd);
>
> - if (ret != NULL)
> - {
> - struct stat64 st;
> -
> - *_fitoa_word (fd, __stpcpy (ret, "/proc/self/fd/"), 10, 0) = '\0';
> -
> - /* We must make sure the file exists. */
> - if (__lxstat64 (_STAT_VER, ret, &st) < 0)
> - {
> - /* /proc is not mounted or something else happened. Don't
> - return the file name. */
> - free (ret);
> - ret = NULL;
> - }
> - }
> - return ret;
> + /* We must make sure the file exists. */
> + if (__lxstat64 (_STAT_VER, buf, & (struct stat64) {}) < 0)
> + /* /proc is not mounted or something else happened. */
> + return false;
> + return true;
> }
>