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1.1 root 1: Info file gcc.info, produced by Makeinfo, -*- Text -*- from input
2: file gcc.texinfo.
3:
4: This file documents the use and the internals of the GNU compiler.
5:
6: Copyright (C) 1988, 1989, 1990 Free Software Foundation, Inc.
7:
8: Permission is granted to make and distribute verbatim copies of
9: this manual provided the copyright notice and this permission notice
10: are preserved on all copies.
11:
12: Permission is granted to copy and distribute modified versions of
13: this manual under the conditions for verbatim copying, provided also
14: that the sections entitled "GNU General Public License" and "Protect
15: Your Freedom--Fight `Look And Feel'" are included exactly as in the
16: original, and provided that the entire resulting derived work is
17: distributed under the terms of a permission notice identical to this
18: one.
19:
20: Permission is granted to copy and distribute translations of this
21: manual into another language, under the above conditions for modified
22: versions, except that the sections entitled "GNU General Public
23: License" and "Protect Your Freedom--Fight `Look And Feel'" and this
24: permission notice may be included in translations approved by the
25: Free Software Foundation instead of in the original English.
26:
27:
28: File: gcc.info, Node: Config, Prev: Machine Macros, Up: Top
29:
30: The Configuration File
31: **********************
32:
33: The configuration file `xm-MACHINE.h' contains macro definitions
34: that describe the machine and system on which the compiler is running.
35: Most of the values in it are actually the same on all machines that
36: GNU CC runs on, so large parts of all configuration files are
37: identical. But there are some macros that vary:
38:
39: `FAILURE_EXIT_CODE'
40: A C expression for the status code to be returned when the
41: compiler exits after serious errors.
42:
43: `SUCCESS_EXIT_CODE'
44: A C expression for the status code to be returned when the
45: compiler exits without serious errors.
46:
47: `USE_C_ALLOCA'
48: Define this macro to indicate that the compiler is running with
49: the `alloca' implemented in C. This version of `alloca' can be
50: found in the file `alloca.c'; to use it, you must also alter the
51: `Makefile' variable `ALLOCA'.
52:
53: This macro, unlike most, describes the machine that the compiler
54: is running on, rather than the one the compiler is compiling for.
55: Therefore, it should be set in the `xm-MACHINE.h' file rather
56: than in the `tm-MACHINE.h' file.
57:
58: If you do define this macro, you should probably do it as follows:
59:
60: #ifndef __GNUC__
61: #define USE_C_ALLOCA
62: #else
63: #define alloca __builtin_alloca
64: #endif
65:
66: so that when the compiler is compiled with GNU CC it uses the
67: more efficient built-in `alloca' function.
68:
69: In addition, configuration files for system V define `bcopy',
70: `bzero' and `bcmp' as aliases. Some files define `alloca' as a macro
71: when compiled with GNU CC, in order to take advantage of the benefit
72: of GNU CC's built-in `alloca'.
73:
74:
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