+# Prepare for substituting <stdbool.h> if it is not supported.
+
+AC_DEFUN([AM_STDBOOL_H],
+[
+ AC_REQUIRE([AC_HEADER_STDBOOL])
+
+ # Define two additional variables used in the Makefile substitution.
+
+ if test "$ac_cv_header_stdbool_h" = yes; then
+ STDBOOL_H=''
+ else
+ STDBOOL_H='stdbool.h'
+ fi
+ AC_SUBST([STDBOOL_H])
+
+ if test "$ac_cv_type__Bool" = yes; then
+ HAVE__BOOL=1
+ else
+ HAVE__BOOL=0
+ fi
+ AC_SUBST([HAVE__BOOL])
+])
+
+# This macro is only needed in autoconf <= 2.54. Newer versions of autoconf
+# have this macro built-in.
+