The Configuration File
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The configuration file `xm-MACHINE.h' contains macro definitions
that describe the machine and system on which the compiler is running,
unlike the definitions in `MACHINE.h', which describe the machine for
which the compiler is producing output. Most of the values in
`xm-MACHINE.h' are actually the same on all machines that GCC runs on,
so large parts of all configuration files are identical. But there are
some macros that vary:
`USG'
Define this macro if the host system is System V.
`VMS'
Define this macro if the host system is VMS.
`FATAL_EXIT_CODE'
A C expression for the status code to be returned when the compiler
exits after serious errors.
`SUCCESS_EXIT_CODE'
A C expression for the status code to be returned when the compiler
exits without serious errors.
`HOST_WORDS_BIG_ENDIAN'
Defined if the host machine stores words of multi-word values in
big-endian order. (GCC does not depend on the host byte ordering
within a word.)
`HOST_FLOAT_WORDS_BIG_ENDIAN'
Define this macro to be 1 if the host machine stores `DFmode',
`XFmode' or `TFmode' floating point numbers in memory with the
word containing the sign bit at the lowest address; otherwise,
define it to be zero.
This macro need not be defined if the ordering is the same as for
multi-word integers.
`HOST_FLOAT_FORMAT'
A numeric code distinguishing the floating point format for the
host machine. See `TARGET_FLOAT_FORMAT' in Note:Storage Layout
for the alternatives and default.
`HOST_BITS_PER_CHAR'
A C expression for the number of bits in `char' on the host
machine.
`HOST_BITS_PER_SHORT'
A C expression for the number of bits in `short' on the host
machine.
`HOST_BITS_PER_INT'
A C expression for the number of bits in `int' on the host machine.
`HOST_BITS_PER_LONG'
A C expression for the number of bits in `long' on the host
machine.
`ONLY_INT_FIELDS'
Define this macro to indicate that the host compiler only supports
`int' bit fields, rather than other integral types, including
`enum', as do most C compilers.
`OBSTACK_CHUNK_SIZE'
A C expression for the size of ordinary obstack chunks. If you
don't define this, a usually-reasonable default is used.
`OBSTACK_CHUNK_ALLOC'
The function used to allocate obstack chunks. If you don't define
this, `xmalloc' is used.
`OBSTACK_CHUNK_FREE'
The function used to free obstack chunks. If you don't define
this, `free' is used.
`USE_C_ALLOCA'
Define this macro to indicate that the compiler is running with the
`alloca' implemented in C. This version of `alloca' can be found
in the file `alloca.c'; to use it, you must also alter the
`Makefile' variable `ALLOCA'. (This is done automatically for the
systems on which we know it is needed.)
If you do define this macro, you should probably do it as follows:
#ifndef __GNUC__
#define USE_C_ALLOCA
#else
#define alloca __builtin_alloca
#endif
so that when the compiler is compiled with GCC it uses the more
efficient built-in `alloca' function.
`FUNCTION_CONVERSION_BUG'
Define this macro to indicate that the host compiler does not
properly handle converting a function value to a
pointer-to-function when it is used in an expression.
`MULTIBYTE_CHARS'
Define this macro to enable support for multibyte characters in the
input to GCC. This requires that the host system support the ANSI
C library functions for converting multibyte characters to wide
characters.
`POSIX'
Define this if your system is POSIX.1 compliant.
`NO_SYS_SIGLIST'
Define this if your system *does not* provide the variable
`sys_siglist'.
Some systems do provide this variable, but with a different name
such as `_sys_siglist'. On these systems, you can define
`sys_siglist' as a macro which expands into the name actually
provided.
Autoconf normally defines `SYS_SIGLIST_DECLARED' when it finds a
declaration of `sys_siglist' in the system header files. However,
when you define `sys_siglist' to a different name autoconf will
not automatically define `SYS_SIGLIST_DECLARED'. Therefore, if
you define `sys_siglist', you should also define
`SYS_SIGLIST_DECLARED'.
`USE_PROTOTYPES'
Define this to be 1 if you know that the host compiler supports
prototypes, even if it doesn't define __STDC__, or define it to be
0 if you do not want any prototypes used in compiling GCC. If
`USE_PROTOTYPES' is not defined, it will be determined
automatically whether your compiler supports prototypes by
checking if `__STDC__' is defined.
`NO_MD_PROTOTYPES'
Define this if you wish suppression of prototypes generated from
the machine description file, but to use other prototypes within
GCC. If `USE_PROTOTYPES' is defined to be 0, or the host compiler
does not support prototypes, this macro has no effect.
`MD_CALL_PROTOTYPES'
Define this if you wish to generate prototypes for the `gen_call'
or `gen_call_value' functions generated from the machine
description file. If `USE_PROTOTYPES' is defined to be 0, or the
host compiler does not support prototypes, or `NO_MD_PROTOTYPES'
is defined, this macro has no effect. As soon as all of the
machine descriptions are modified to have the appropriate number
of arguments, this macro will be removed.
`PATH_SEPARATOR'
Define this macro to be a C character constant representing the
character used to separate components in paths. The default value
is the colon character
`DIR_SEPARATOR'
If your system uses some character other than slash to separate
directory names within a file specification, define this macro to
be a C character constant specifying that character. When GCC
displays file names, the character you specify will be used. GCC
will test for both slash and the character you specify when
parsing filenames.
`OBJECT_SUFFIX'
Define this macro to be a C string representing the suffix for
object files on your machine. If you do not define this macro,
GCC will use `.o' as the suffix for object files.
`EXECUTABLE_SUFFIX'
Define this macro to be a C string representing the suffix for
executable files on your machine. If you do not define this
macro, GCC will use the null string as the suffix for object files.
`COLLECT_EXPORT_LIST'
If defined, `collect2' will scan the individual object files
specified on its command line and create an export list for the
linker. Define this macro for systems like AIX, where the linker
discards object files that are not referenced from `main' and uses
export lists.
In addition, configuration files for system V define `bcopy',
`bzero' and `bcmp' as aliases. Some files define `alloca' as a macro
when compiled with GCC, in order to take advantage of the benefit of
GCC's built-in `alloca'.