posix/execl.c

   1 /* Copyright (C) 1991, 92, 94, 97, 98, 99 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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 #include <stackinfo.h>
  26
  27 #ifndef HAVE_GNU_LD
  28 # define __environ      environ
  29 #endif
  30
  31 /* Execute PATH with all arguments after PATH until
  32    a NULL pointer and environment from `environ'.  */
  33 int
  34 execl (const char *path, const char *arg, ...)
  35 {
  36   size_t argv_max = 1024;
  37   const char **argv = alloca (argv_max * sizeof (const char *));
  38   unsigned int i;
  39   va_list args;
  40
  41   argv[0] = arg;
  42
  43   va_start (args, arg);
  44   i = 0;
  45   while (argv[i++] != NULL)
  46     {
  47       if (i == argv_max)
  48         {
  49           const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));
  50
  51 #ifndef _STACK_GROWS_UP
  52           if ((char *) nptr + argv_max == (char *) argv)
  53             {
  54               /* Stack grows down.  */
  55               argv = (const char **) memcpy (nptr, argv,
  56                                              i * sizeof (const char *));
  57               argv_max += i;
  58             }
  59           else
  60 #endif
  61 #ifndef _STACK_GROWS_DOWN
  62             if ((char *) argv + i == (char *) nptr)
  63             /* Stack grows up.  */
  64             argv_max += i;
  65           else
  66 #endif
  67             /* We have a hole in the stack.  */
  68             argv = (const char **) memcpy (nptr, argv,
  69                                            i * sizeof (const char *));
  70         }
  71
  72       argv[i] = va_arg (args, const char *);
  73     }
  74   va_end (args);
  75
  76   return __execve (path, (char *const *) argv, __environ);
  77 }