Rewrite globals to allow indirection in C.
[emacs.git] / src / ecrt0.c
blob7dbbd6c5ef130480046b48b14932e54f69d9b1f7
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.
5 This file is part of GNU Emacs.
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.
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.
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/>. */
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. */
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
33 Optionally:
34 [word pointing to environment variable]... 1 or more times
35 ...
37 And always:
38 first arg string
39 [next arg string]... 0 or more times
42 #ifdef emacs
43 #include <config.h>
44 #endif
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. */
60 int data_start = 0;
62 #ifdef NEED_ERRNO
63 int errno;
64 #endif
66 #ifndef MSDOS
67 char **environ;
68 #endif
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
78 #ifdef CRT0_DUMMIES
80 /* Define symbol "start": here; some systems want that symbol. */
81 asm(" .text ");
82 asm(" .globl start ");
83 asm(" start: ");
85 _start ()
87 /* On vax, nothing is pushed here */
88 start1 ();
91 static
92 start1 (CRT0_DUMMIES argc, xargv)
93 int argc;
94 char *xargv;
96 register char **argv = &xargv;
97 environ = argv + argc + 1;
99 if ((char *)environ == xargv)
100 environ--;
101 exit (main (argc, argv, environ));
103 /* Refer to `start1' so GCC will not think it is never called
104 and optimize it out. */
105 (void) &start1;
107 #else /* not CRT0_DUMMIES */
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. */
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");
130 /* ignore takes care of skipping the a6 value pushed in start. */
131 static
132 start1 (argc, xargv)
133 int argc;
134 char *xargv;
136 register char **argv = &xargv;
137 environ = argv + argc + 1;
139 if ((char *)environ == xargv)
140 environ--;
141 exit (main (argc, argv, environ));
144 #endif /* m68k */
146 #endif /* not CRT0_DUMMIES */
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");
166 #endif /* __sparc__ */
168 #if __FreeBSD__ == 2
169 char *__progname;
170 #endif
172 /* arch-tag: 4025c2fb-d6b1-4d29-b1b6-8100b6bd1e74
173 (do not change this comment) */