|  | # Check compiler characteristics (e.g. type sizes, PRIxx macros, ...) | 
|  |  | 
|  | # If types $1 and $2 are compatible, perform action $3 | 
|  | AC_DEFUN([AC_TYPES_COMPATIBLE], | 
|  | [AC_TRY_COMPILE([#include <stddef.h>], [$1 v1 = 0; $2 v2 = 0; return (&v1 - &v2)], $3)]) | 
|  |  | 
|  | define(AC_PRIUS_COMMENT, [printf format code for printing a size_t and ssize_t]) | 
|  |  | 
|  | AC_DEFUN([AC_COMPILER_CHARACTERISTICS], | 
|  | [AC_CACHE_CHECK(AC_PRIUS_COMMENT, ac_cv_formatting_prius_prefix, | 
|  | [AC_TYPES_COMPATIBLE(unsigned int, size_t, | 
|  | ac_cv_formatting_prius_prefix=; ac_cv_prius_defined=1) | 
|  | AC_TYPES_COMPATIBLE(unsigned long, size_t, | 
|  | ac_cv_formatting_prius_prefix=l; ac_cv_prius_defined=1) | 
|  | AC_TYPES_COMPATIBLE(unsigned long long, size_t, | 
|  | ac_cv_formatting_prius_prefix=ll; ac_cv_prius_defined=1 | 
|  | )]) | 
|  | if test -z "$ac_cv_prius_defined"; then | 
|  | ac_cv_formatting_prius_prefix=z; | 
|  | fi | 
|  | AC_DEFINE_UNQUOTED(PRIuS, "${ac_cv_formatting_prius_prefix}u", AC_PRIUS_COMMENT) | 
|  | AC_DEFINE_UNQUOTED(PRIxS, "${ac_cv_formatting_prius_prefix}x", AC_PRIUS_COMMENT) | 
|  | AC_DEFINE_UNQUOTED(PRIdS, "${ac_cv_formatting_prius_prefix}d", AC_PRIUS_COMMENT) | 
|  | ]) |