src/ecrt0.c

   1 /* C code startup routine.
   2    Copyright (C) 1985, 1986, 1992, 2001, 2002, 2003, 2004,
   3                  2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software: you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation, either version 3 of the License, or
  10 (at your option) any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* The standard Vax 4.2 Unix crt0.c cannot be used for Emacs
  22    because it makes `environ' an initialized variable.
  23    It is easiest to have a special crt0.c on all machines
  24    though I don't know whether other machines actually need it.  */
  25
  26 /* On the vax and 68000, in BSD4.2 and USG5.2,
  27    this is the data format on startup:
  28   (vax) ap and fp are unpredictable as far as I know; don't use them.
  29   sp ->  word containing argc
  30          word pointing to first arg string
  31          [word pointing to next arg string]... 0 or more times
  32          0
  33 Optionally:
  34          [word pointing to environment variable]... 1 or more times
  35          ...
  36          0
  37 And always:
  38          first arg string
  39          [next arg string]... 0 or more times
  40 */
  41
  42 #ifdef emacs
  43 #include <config.h>
  44 #endif
  45
  46 /*              ********  WARNING ********
  47     Do not insert any data definitions before data_start!
  48     Since this is the first file linked, the address of the following
  49     variable should correspond to the start of initialized data space.
  50     On some systems this is a constant that is independent of the text
  51     size for shared executables.  On others, it is a function of the
  52     text size. In short, this seems to be the most portable way to
  53     discover the start of initialized data space dynamically at runtime,
  54     for either shared or unshared executables, on either swapping or
  55     virtual systems.  It only requires that the linker allocate objects
  56     in the order encountered, a reasonable model for most Unix systems.
  57     Similarly, note that the address of _start() should be the start
  58     of text space.   Fred Fish, UniSoft Systems Inc.  */
  59
  60 int data_start = 0;
  61
  62 char **environ;
  63
  64 static start1 ();
  65
  66 /* Define symbol "start": here; some systems want that symbol.  */
  67 asm("   .text           ");
  68 asm("   .globl start    ");
  69 asm("   start:          ");
  70
  71 _start ()
  72 {
  73 /* On vax, nothing is pushed here  */
  74   start1 ();
  75 }
  76
  77 static
  78 start1 (bogus_fp, argc, xargv)
  79      int argc;
  80      char *xargv;
  81 {
  82   register char **argv = &xargv;
  83   environ = argv + argc + 1;
  84
  85   if ((char *)environ == xargv)
  86     environ--;
  87   exit (main (argc, argv, environ));
  88
  89   /* Refer to `start1' so GCC will not think it is never called
  90      and optimize it out.  */
  91   (void) &start1;
  92 }
  93
  94 /* arch-tag: 4025c2fb-d6b1-4d29-b1b6-8100b6bd1e74
  95    (do not change this comment) */