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AC_DEFINE_INTEGER_BITS (TYPE [, CANDIDATE-TYPE]...)
1.1 (2002/03/17) Miscellaneous @ ac-archive-0.5.39
Scott Pakin <pakin@uiuc.edu>
Given a TYPE of the form "int##_t" or "uint##_t", see if the datatype TYPE is predefined. If not, then define TYPE -- both with AC_DEFINE and as a shell variable -- to the first datatype of exactly ## bits in a list of CANDIDATE-TYPEs. If none of the CANDIDATE-TYPEs contains exactly ## bits, then set the TYPE shell variable to "no".
For example, the following ensures that uint64_t is defined as a 64-bit datatype:
AC_DEFINE_INTEGER_BITS(uint64_t, unsigned long long, unsigned __int64, long)
if test "$uint64_t" = no; then
AC_MSG_ERROR([unable to continue without a 64-bit datatype])
fi
You should then put the following in your C code to ensure that all datatypes defined by AC_DEFINE_INTEGER_BITS are visible to your program:
#include "config.h"
#if HAVE_INTTYPES_H
# include <inttypes.h>
#else
# if HAVE_STDINT_H
# include <stdint.h>
# endif
#endif
AC_DEFUN([AC_DEFINE_INTEGER_BITS], [m4_define([ac_datatype_bits], [m4_translit($1, [a-zA-Z_])]) m4_define([ac_datatype_bytes], [m4_eval(ac_datatype_bits/8)]) AC_CHECK_TYPE($1, , [ AC_MSG_NOTICE([trying to find a suitable ]ac_datatype_bytes[-byte replacement for $1]) $1=no find_$1 () { _AC_DEFINE_INTEGER_BITS_HELPER($@) : } find_$1 AC_DEFINE_UNQUOTED($1, $$1, [If not already defined, then define as a datatype of *exactly* ]ac_datatype_bits[ bits.]) ]) ]) dnl Iterate over arguments $2..$N, trying to find a good match for $1. m4_define([_AC_DEFINE_INTEGER_BITS_HELPER], [ifelse($2, , , [m4_define([ac_datatype_bits], [m4_translit($1, [a-zA-Z_])]) m4_define([ac_datatype_bytes], [m4_eval(ac_datatype_bits/8)]) AC_CHECK_SIZEOF($2) if test "$AS_TR_SH(ac_cv_sizeof_$2)" -eq ac_datatype_bytes; then $1="$2" return fi _AC_DEFINE_INTEGER_BITS_HELPER($1, m4_shift(m4_shift($@))) ]) ])