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 #ifndef MSDOS
  63 char **environ;
  64 #endif
  65
  66 #ifndef static
  67 /* On systems where the static storage class is usable, this function
  68    should be declared as static.  Otherwise, the static keyword has
  69    been defined to be something else, and code for those systems must
  70    take care of this declaration appropriately.  */
  71 static start1 ();
  72 #endif
  73
  74 #ifdef CRT0_DUMMIES
  75
  76 /* Define symbol "start": here; some systems want that symbol.  */
  77 asm("   .text           ");
  78 asm("   .globl start    ");
  79 asm("   start:          ");
  80
  81 _start ()
  82 {
  83 /* On vax, nothing is pushed here  */
  84   start1 ();
  85 }
  86
  87 static
  88 start1 (CRT0_DUMMIES argc, xargv)
  89      int argc;
  90      char *xargv;
  91 {
  92   register char **argv = &xargv;
  93   environ = argv + argc + 1;
  94
  95   if ((char *)environ == xargv)
  96     environ--;
  97   exit (main (argc, argv, environ));
  98
  99   /* Refer to `start1' so GCC will not think it is never called
 100      and optimize it out.  */
 101   (void) &start1;
 102 }
 103 #else /* not CRT0_DUMMIES */
 104
 105 /* This is a kludge.  Now that the CRT0_DUMMIES mechanism above exists,
 106    most of these machines could use the vax code above
 107    with some suitable definition of CRT0_DUMMIES.
 108    Then the symbol m68k could be flushed.
 109    But I don't want to risk breaking these machines
 110    in a version 17 patch release, so that change is being put off.  */
 111
 112 #ifdef m68k                     /* Can't do it all from C */
 113         asm ("  global  _start");
 114         asm ("  text");
 115         asm ("_start:");
 116         asm ("  comm    splimit%,4");
 117         asm ("  global  exit");
 118         asm ("  text");
 119         asm ("  mov.l   %d0,splimit%");
 120         asm ("  jsr     start1");
 121         asm ("  mov.l   %d0,(%sp)");
 122         asm ("  jsr     exit");
 123         asm ("  mov.l   &1,%d0");       /* d0 = 1 => exit */
 124         asm ("  trap    &0");
 125
 126 /* ignore takes care of skipping the a6 value pushed in start.  */
 127 static
 128 start1 (argc, xargv)
 129      int argc;
 130      char *xargv;
 131 {
 132   register char **argv = &xargv;
 133   environ = argv + argc + 1;
 134
 135   if ((char *)environ == xargv)
 136     environ--;
 137   exit (main (argc, argv, environ));
 138 }
 139
 140 #endif /* m68k */
 141
 142 #endif /* not CRT0_DUMMIES */
 143
 144 #ifdef __sparc__
 145 asm (".global __start");
 146 asm (".text");
 147 asm ("__start:");
 148 asm ("  mov     0, %fp");
 149 asm ("  ld      [%sp + 64], %o0");
 150 asm ("  add     %sp, 68, %o1");
 151 asm ("  sll     %o0, 2, %o2");
 152 asm ("  add     %o2, 4, %o2");
 153 asm ("  add     %o1, %o2, %o2");
 154 asm ("  sethi   %hi(_environ), %o3");
 155 asm ("  st      %o2, [%o3+%lo(_environ)]");
 156 asm ("  andn    %sp, 7, %sp");
 157 asm ("  call    _main");
 158 asm ("  sub     %sp, 24, %sp");
 159 asm ("  call    __exit");
 160 asm ("  nop");
 161
 162 #endif /* __sparc__ */
 163
 164 #if __FreeBSD__ == 2
 165 char *__progname;
 166 #endif
 167
 168 /* arch-tag: 4025c2fb-d6b1-4d29-b1b6-8100b6bd1e74
 169    (do not change this comment) */