stdlib/putenv.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #if defined _AIX && !defined __GNUC__
  19  #pragma alloca
  20 #endif
  21
  22 #if HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #if _LIBC || HAVE_STDLIB_H
  27 # include <stdlib.h>
  28 #endif
  29 #if _LIBC || HAVE_STRING_H
  30 # include <string.h>
  31 #endif
  32
  33 #if !__GNU_LIBRARY__ && !HAVE_STRCHR
  34 # define strchr index
  35 #endif
  36
  37 #ifndef _LIBC
  38 # ifdef HAVE_ALLOCA_H
  39 #  include <alloca.h>
  40 # else
  41 #  ifdef __GNUC__
  42 #   define alloca __builtin_alloca
  43 #  else
  44 extern char *alloca ();
  45 #  endif /* __GNUC__ */
  46 # endif /* HAVE_ALLOCA_H */
  47 #endif /* _LIBC */
  48
  49
  50 /* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
  51 int
  52 putenv (char *string)
  53 {
  54   const char *const name_end = strchr (string, '=');
  55
  56   if (name_end != NULL)
  57     {
  58       char *name;
  59 #ifdef _LIBC
  60       int use_malloc = !__libc_use_alloca (name_end - string + 1);
  61       if (__builtin_expect (use_malloc, 0))
  62         {
  63           name = __strndup (string, name_end - string);
  64           if (name == NULL)
  65             return -1;
  66         }
  67       else
  68         name = strndupa (string, name_end - string);
  69 #else
  70 # define use_malloc 1
  71       name = malloc (name_end - string + 1);
  72       if (name == NULL)
  73         return -1;
  74       memcpy (name, string, name_end - string);
  75       name[name_end - string] = '\0';
  76 #endif
  77       int result = __add_to_environ (name, NULL, string, 1);
  78
  79       if (__glibc_unlikely (use_malloc))
  80         free (name);
  81
  82       return result;
  83     }
  84
  85   __unsetenv (string);
  86   return 0;
  87 }