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 #ifdef NEED_ERRNO
  63 int errno;
  64 #endif
  65
  66 #ifndef MSDOS
  67 char **environ;
  68 #endif
  69
  70 #ifndef static
  71 /* On systems where the static storage class is usable, this function
  72    should be declared as static.  Otherwise, the static keyword has
  73    been defined to be something else, and code for those systems must
  74    take care of this declaration appropriately.  */
  75 static start1 ();
  76 #endif
  77
  78 #ifdef CRT0_DUMMIES
  79
  80 /* Define symbol "start": here; some systems want that symbol.  */
  81 asm("   .text           ");
  82 asm("   .globl start    ");
  83 asm("   start:          ");
  84
  85 _start ()
  86 {
  87 /* On vax, nothing is pushed here  */
  88   start1 ();
  89 }
  90
  91 static
  92 start1 (CRT0_DUMMIES argc, xargv)
  93      int argc;
  94      char *xargv;
  95 {
  96   register char **argv = &xargv;
  97   environ = argv + argc + 1;
  98
  99   if ((char *)environ == xargv)
 100     environ--;
 101   exit (main (argc, argv, environ));
 102
 103   /* Refer to `start1' so GCC will not think it is never called
 104      and optimize it out.  */
 105   (void) &start1;
 106 }
 107 #else /* not CRT0_DUMMIES */
 108
 109 /* This is a kludge.  Now that the CRT0_DUMMIES mechanism above exists,
 110    most of these machines could use the vax code above
 111    with some suitable definition of CRT0_DUMMIES.
 112    Then the symbol m68k could be flushed.
 113    But I don't want to risk breaking these machines
 114    in a version 17 patch release, so that change is being put off.  */
 115
 116 #ifdef m68k                     /* Can't do it all from C */
 117         asm ("  global  _start");
 118         asm ("  text");
 119         asm ("_start:");
 120         asm ("  comm    splimit%,4");
 121         asm ("  global  exit");
 122         asm ("  text");
 123         asm ("  mov.l   %d0,splimit%");
 124         asm ("  jsr     start1");
 125         asm ("  mov.l   %d0,(%sp)");
 126         asm ("  jsr     exit");
 127         asm ("  mov.l   &1,%d0");       /* d0 = 1 => exit */
 128         asm ("  trap    &0");
 129
 130 /* ignore takes care of skipping the a6 value pushed in start.  */
 131 static
 132 start1 (argc, xargv)
 133      int argc;
 134      char *xargv;
 135 {
 136   register char **argv = &xargv;
 137   environ = argv + argc + 1;
 138
 139   if ((char *)environ == xargv)
 140     environ--;
 141   exit (main (argc, argv, environ));
 142 }
 143
 144 #endif /* m68k */
 145
 146 #endif /* not CRT0_DUMMIES */
 147
 148 #ifdef __sparc__
 149 asm (".global __start");
 150 asm (".text");
 151 asm ("__start:");
 152 asm ("  mov     0, %fp");
 153 asm ("  ld      [%sp + 64], %o0");
 154 asm ("  add     %sp, 68, %o1");
 155 asm ("  sll     %o0, 2, %o2");
 156 asm ("  add     %o2, 4, %o2");
 157 asm ("  add     %o1, %o2, %o2");
 158 asm ("  sethi   %hi(_environ), %o3");
 159 asm ("  st      %o2, [%o3+%lo(_environ)]");
 160 asm ("  andn    %sp, 7, %sp");
 161 asm ("  call    _main");
 162 asm ("  sub     %sp, 24, %sp");
 163 asm ("  call    __exit");
 164 asm ("  nop");
 165
 166 #endif /* __sparc__ */
 167
 168 #if __FreeBSD__ == 2
 169 char *__progname;
 170 #endif
 171
 172 /* arch-tag: 4025c2fb-d6b1-4d29-b1b6-8100b6bd1e74
 173    (do not change this comment) */