Re: [PATCH] libio: Flush stream at freopen (BZ#21037)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

Ping (x2).

On 08/08/2017 10:52, Adhemerval Zanella wrote:
> 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;
>>  }
>>