ac_check_typedef

check if the given typedef-name is recognized as a type. The trick is to use a sizeof(TYPEDEF) and see if the compiler is happy with that.

this can be thought of as a mixture of AC_CHECK_TYPE(TYPEDEF,DEFAULT) and AC_CHECK_LIB(LIBRARY,FUNCTION,ACTION-IF-FOUND,ACTION-IF-NOT-FOUND)

a convenience macro AC_CHECK_TYPEDEF_ is provided that will not emit any message to the user - it just executes one of the actions.

AC_DEFUN(AC_CHECK_TYPEDEF_,
[dnl
ac_lib_var=`echo $1['_']$2 | sed 'y%./+-%__p_%'`
AC_CACHE_VAL(ac_cv_lib_$ac_lib_var,
[ eval "ac_cv_type_$ac_lib_var='not-found'"
  ac_cv_check_typedef_header=`echo ifelse([$2], , stddef.h, $2)`
  AC_TRY_COMPILE( [#include <$ac_cv_check_typedef_header>], 
	[int x = sizeof($1); x = x;],
        eval "ac_cv_type_$ac_lib_var=yes" ,
        eval "ac_cv_type_$ac_lib_var=no" )
  if test `eval echo '$ac_cv_type_'$ac_lib_var` = "no" ; then 
     ifelse([$4], , :, $4)
  else 
     ifelse([$3], , :, $3) 
  fi
])])

dnl AC_CHECK_TYPEDEF(TYPEDEF, HEADER [, ACTION-IF-FOUND,
dnl    [, ACTION-IF-NOT-FOUND ]])
AC_DEFUN(AC_CHECK_TYPEDEF,
[dnl
 AC_MSG_CHECKING([for $1 in $2])
 AC_CHECK_TYPEDEF_($1,$2,AC_MSG_RESULT(yes),AC_MSG_RESULT(no))dnl
])