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glibc  2.9
tmpnam.c
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00001 /* Copyright (C) 1991,1993,1996-1999,2000,2007 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public
00006    License as published by the Free Software Foundation; either
00007    version 2.1 of the License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; if not, write to the Free
00016    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00017    02111-1307 USA.  */
00018 
00019 #include <stdio.h>
00020 #include <string.h>
00021 
00022 static char tmpnam_buffer[L_tmpnam];
00023 
00024 /* Generate a unique filename in P_tmpdir.
00025 
00026    This function is *not* thread safe!  */
00027 char *
00028 tmpnam (char *s)
00029 {
00030   /* By using two buffers we manage to be thread safe in the case
00031      where S != NULL.  */
00032   char tmpbufmem[L_tmpnam];
00033   char *tmpbuf = s ?: tmpbufmem;
00034 
00035   /* In the following call we use the buffer pointed to by S if
00036      non-NULL although we don't know the size.  But we limit the size
00037      to L_tmpnam characters in any case.  */
00038   if (__builtin_expect (__path_search (tmpbuf, L_tmpnam, NULL, NULL, 0),
00039                      0))
00040     return NULL;
00041 
00042   if (__builtin_expect (__gen_tempname (tmpbuf, 0, __GT_NOCREATE), 0))
00043     return NULL;
00044 
00045   if (s == NULL)
00046     return (char *) memcpy (tmpnam_buffer, tmpbuf, L_tmpnam);
00047 
00048   return s;
00049 }
00050 
00051 link_warning (tmpnam,
00052              "the use of `tmpnam' is dangerous, better use `mkstemp'")