The following macros check for C compiler or machine architecture
features. To check for characteristics not listed here, use
AC_TRY_COMPILE (see section Examining Syntax) or AC_TRY_RUN
(see section Checking Run Time Behavior)
WORDS_BIGENDIAN.
const,
define const to be empty. Some C compilers that do not define
__STDC__ do support const; some compilers that define
__STDC__ do not completely support const. Programs can
simply use const as if every C compiler supported it; for those
that don't, the `Makefile' or configuration header file will define
it as empty.
inline, do nothing.
Otherwise define inline to __inline__ or __inline
if it accepts one of those, otherwise define inline to be empty.
char is unsigned, define __CHAR_UNSIGNED__,
unless the C compiler predefines it.
long double type, define
HAVE_LONG_DOUBLE. Some C compilers that do not define
__STDC__ do support the long double type; some compilers
that define __STDC__ do not support long double.
HAVE_STRINGIZE. The stringizing operator is `#' and is
found in macros such as this:
#define x(y) #y
SIZEOF_uctype to be the size in bytes of the C (or
C++) builtin type type, e.g. `int' or `char *'. If
`type' is unknown to the compiler, it gets a size of 0. uctype
is type, with lowercase converted to uppercase, spaces changed to
underscores, and asterisks changed to `P'. If cross-compiling, the
value cross-size is used if given, otherwise configure
exits with an error message.
For example, the call
AC_CHECK_SIZEOF(int *)
defines SIZEOF_INT_P to be 8 on DEC Alpha AXP systems.
int is 16 bits wide, define INT_16_BITS.
This macro is obsolete; it is more general to use
`AC_CHECK_SIZEOF(int)' instead.
long int is 64 bits wide, define
LONG_64_BITS. This macro is obsolete; it is more general to use
`AC_CHECK_SIZEOF(long)' instead.
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