posix/execl.c

   1 /* Copyright (C) 1991, 1992, 1994, 1997, 1998 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 Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    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    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <alloca.h>
  20 #include <unistd.h>
  21 #include <stdarg.h>
  22 #include <stddef.h>
  23 #include <string.h>
  24
  25 #ifndef HAVE_GNU_LD
  26 # define __environ      environ
  27 #endif
  28
  29 /* Execute PATH with all arguments after PATH until
  30    a NULL pointer and environment from `environ'.  */
  31 int
  32 execl (const char *path, const char *arg, ...)
  33 {
  34   size_t argv_max = 1024;
  35   const char **argv = alloca (argv_max * sizeof (const char *));
  36   unsigned int i;
  37   va_list args;
  38
  39   argv[0] = arg;
  40
  41   va_start (args, arg);
  42   i = 0;
  43   while (argv[i++] != NULL)
  44     {
  45       if (i == argv_max)
  46         {
  47           const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));
  48
  49           if ((char *) nptr + argv_max == (char *) argv)
  50             {
  51               /* Stack grows down.  */
  52               argv = (const char **) memcpy (nptr, argv, i);
  53               argv_max += i;
  54             }
  55           else if ((char *) argv + i == (char *) nptr)
  56             /* Stack grows up.  */
  57             argv_max += i;
  58           else
  59             /* We have a hole in the stack.  */
  60             argv = (const char **) memcpy (nptr, argv, i);
  61         }
  62
  63       argv[i] = va_arg (args, const char *);
  64     }
  65   va_end (args);
  66
  67   return __execve (path, (char *const *) argv, __environ);
  68 }