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
(see section Checking Run Time Behavior)
constto be empty. Some C compilers that do not define
const; some compilers that define
__STDC__do not completely support
const. Programs can simply use
constas 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
__inlineif it accepts one of those, otherwise define
inlineto be empty.
charis unsigned, define
__CHAR_UNSIGNED__, unless the C compiler predefines it.
long doubletype, define
HAVE_LONG_DOUBLE. Some C compilers that do not define
__STDC__do support the
long doubletype; some compilers that define
__STDC__do not support
HAVE_STRINGIZE. The stringizing operator is `#' and is found in macros such as this:
#define x(y) #y
SIZEOF_uctypeto 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
configureexits with an error message.
For example, the call
SIZEOF_INT_P to be 8 on DEC Alpha AXP systems.
intis 16 bits wide, define
INT_16_BITS. This macro is obsolete; it is more general to use `AC_CHECK_SIZEOF(int)' instead.
long intis 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 This macro is obsolete; it is more general to use `AC_CHECK_SIZEOF(long)' instead.
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