info autoconf

5.9.1 Particular Type Checks

These macros check for particular C types in ‘sys/types.h’, ‘stdlib.h’, ‘stdint.h’, ‘inttypes.h’ and others, if they exist.

The Gnulib stdint module is an alternate way to define many of these symbols; it is useful if you prefer your code to assume a C99-or-better environment. See section Gnulib.

Macro: AC_TYPE_GETGROUPS: Define GETGROUPS_T to be whichever of gid_t or int is the base type of the array argument to getgroups.

Macro: AC_TYPE_INT8_T

If ‘stdint.h’ or ‘inttypes.h’ does not define the type int8_t, define int8_t to a signed integer type that is exactly 8 bits wide and that uses two's complement representation, if such a type exists. If you are worried about porting to hosts that lack such a type, you can use the results of this macro in C89-or-later code as follows:

#if HAVE_STDINT_H
# include <stdint.h>
#endif
#if defined INT8_MAX || defined int8_t
 code using int8_t
#else
 complicated alternative using >8-bit 'signed char'
#endif

Macro: AC_TYPE_INT16_T: This is like AC_TYPE_INT8_T, except for 16-bit integers.

Macro: AC_TYPE_INT32_T: This is like AC_TYPE_INT8_T, except for 32-bit integers.

Macro: AC_TYPE_INT64_T: This is like AC_TYPE_INT8_T, except for 64-bit integers.

Macro: AC_TYPE_INTMAX_T: If ‘stdint.h’ or ‘inttypes.h’ defines the type intmax_t, define HAVE_INTMAX_T. Otherwise, define intmax_t to the widest signed integer type.

Macro: AC_TYPE_INTPTR_T: If ‘stdint.h’ or ‘inttypes.h’ defines the type intptr_t, define HAVE_INTPTR_T. Otherwise, define intptr_t to a signed integer type wide enough to hold a pointer, if such a type exists.

Macro: AC_TYPE_LONG_DOUBLE

If the C compiler supports a working long double type, define HAVE_LONG_DOUBLE. The long double type might have the same range and precision as double.

This macro is obsolescent, as current C compilers support long double. New programs need not use this macro.

Macro: AC_TYPE_LONG_DOUBLE_WIDER: If the C compiler supports a working long double type with more range or precision than the double type, define HAVE_LONG_DOUBLE_WIDER.

Macro: AC_TYPE_LONG_LONG_INT: If the C compiler supports a working long long int type, define HAVE_LONG_LONG_INT. However, this test does not test long long int values in preprocessor #if expressions, because too many compilers mishandle such expressions. See section Preprocessor Arithmetic.

Macro: AC_TYPE_MBSTATE_T: Define HAVE_MBSTATE_T if <wchar.h> declares the mbstate_t type. Also, define mbstate_t to be a type if <wchar.h> does not declare it.

Macro: AC_TYPE_MODE_T: Define mode_t to a suitable type, if standard headers do not define it.

Macro: AC_TYPE_OFF_T: Define off_t to a suitable type, if standard headers do not define it.

Macro: AC_TYPE_PID_T: Define pid_t to a suitable type, if standard headers do not define it.

Macro: AC_TYPE_SIZE_T: Define size_t to a suitable type, if standard headers do not define it.

Macro: AC_TYPE_SSIZE_T: Define ssize_t to a suitable type, if standard headers do not define it.

Macro: AC_TYPE_UID_T: Define uid_t and gid_t to suitable types, if standard headers do not define them.

Macro: AC_TYPE_UINT8_T: If ‘stdint.h’ or ‘inttypes.h’ does not define the type uint8_t, define uint8_t to an unsigned integer type that is exactly 8 bits wide, if such a type exists. This is like AC_TYPE_INT8_T, except for unsigned integers.

Macro: AC_TYPE_UINT16_T: This is like AC_TYPE_UINT8_T, except for 16-bit integers.

Macro: AC_TYPE_UINT32_T: This is like AC_TYPE_UINT8_T, except for 32-bit integers.

Macro: AC_TYPE_UINT64_T: This is like AC_TYPE_UINT8_T, except for 64-bit integers.

Macro: AC_TYPE_UINTMAX_T: If ‘stdint.h’ or ‘inttypes.h’ defines the type uintmax_t, define HAVE_UINTMAX_T. Otherwise, define uintmax_t to the widest unsigned integer type.

Macro: AC_TYPE_UINTPTR_T: If ‘stdint.h’ or ‘inttypes.h’ defines the type uintptr_t, define HAVE_UINTPTR_T. Otherwise, define uintptr_t to an unsigned integer type wide enough to hold a pointer, if such a type exists.

Macro: AC_TYPE_UNSIGNED_LONG_LONG_INT: If the C compiler supports a working unsigned long long int type, define HAVE_UNSIGNED_LONG_LONG_INT. However, this test does not test unsigned long long int values in preprocessor #if expressions, because too many compilers mishandle such expressions. See section Preprocessor Arithmetic.

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