lib/fclose.c

   1 /* fclose replacement.
   2    Copyright (C) 2008-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <stdio.h>
  21
  22 #include <errno.h>
  23 #include <unistd.h>
  24
  25 #include "freading.h"
  26 #if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  27 # include "msvc-inval.h"
  28 #endif
  29
  30 #undef fclose
  31
  32 #if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  33 static int
  34 fclose_nothrow (FILE *fp)
  35 {
  36   int result;
  37
  38   TRY_MSVC_INVAL
  39     {
  40       result = fclose (fp);
  41     }
  42   CATCH_MSVC_INVAL
  43     {
  44       result = EOF;
  45       errno = EBADF;
  46     }
  47   DONE_MSVC_INVAL;
  48
  49   return result;
  50 }
  51 #else
  52 # define fclose_nothrow fclose
  53 #endif
  54
  55 /* Override fclose() to call the overridden fflush() or close().  */
  56
  57 int
  58 rpl_fclose (FILE *fp)
  59 {
  60   int saved_errno = 0;
  61   int fd;
  62   int result = 0;
  63
  64   /* Don't change behavior on memstreams.  */
  65   fd = fileno (fp);
  66   if (fd < 0)
  67     return fclose_nothrow (fp);
  68
  69   /* We only need to flush the file if it is not reading or if it is
  70      seekable.  This only guarantees the file position of input files
  71      if the fflush module is also in use.  */
  72   if ((!freading (fp) || lseek (fileno (fp), 0, SEEK_CUR) != -1)
  73       && fflush (fp))
  74     saved_errno = errno;
  75
  76   /* fclose() calls close(), but we need to also invoke all hooks that our
  77      overridden close() function invokes.  See lib/close.c.  */
  78 #if WINDOWS_SOCKETS
  79   /* Call the overridden close(), then the original fclose().
  80      Note about multithread-safety: There is a race condition where some
  81      other thread could open fd between our close and fclose.  */
  82   if (close (fd) < 0 && saved_errno == 0)
  83     saved_errno = errno;
  84
  85   fclose_nothrow (fp); /* will fail with errno = EBADF,
  86                           if we did not lose a race */
  87
  88 #else /* !WINDOWS_SOCKETS */
  89   /* Call fclose() and invoke all hooks of the overridden close().  */
  90
  91 # if REPLACE_FCHDIR
  92   /* Note about multithread-safety: There is a race condition here as well.
  93      Some other thread could open fd between our calls to fclose and
  94      _gl_unregister_fd.  */
  95   result = fclose_nothrow (fp);
  96   if (result == 0)
  97     _gl_unregister_fd (fd);
  98 # else
  99   /* No race condition here.  */
 100   result = fclose_nothrow (fp);
 101 # endif
 102
 103 #endif /* !WINDOWS_SOCKETS */
 104
 105   if (saved_errno != 0)
 106     {
 107       errno = saved_errno;
 108       result = EOF;
 109     }
 110
 111   return result;
 112 }