#include <stdbool.h>

17+ years passed since standardized in ISO, 8 years since we added
AC_HEADER_STDBOOL to configure.in.  I'm quite confident that it's
already safe to use <stdbool.h>.

I understand that when we introduced AC_HEADER_STDBOOL, <stdbool.h>
was remain not included because C standard and SVR4 curses conflicted
miserably back then (#1).  Though I believe such situation has been
fixed already(#2), I'm afraid of your operating system might ship a
proprietary curses that still conflicts with the standard. So to avoid
potential problem, we limit the inclusion to our internal use only.

#1 : 1997 version of SUSv2 said bool is "defined though typedef" in
     <curses.h>, while C99 said bool is a macro, plus in C++ bool is a
     keyword.  AFASIK the curses library has never been a part of
     POSIX.

#2 : In reality ncurses and NetBSD curses both just follow C99 to
     include <stdbool.h> from <curses.h>.  I think C99 is now widely
     adopted.

----

	* internal.h: #include <stdbool.h> if present.  That is
	  believed to be the case for 99.9% systems that lives today.
	  Non-C99, non-C++ situations are intentionally left
	  undefined, advised by Motohiro Kosaki.  If you have such
	  compiler, please fill the definition appropriately.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57460 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

internal.h

@@ -23,6 +23,19 @@ extern "C" {
 #endif
 #endif
 
+#ifdef HAVE_STDBOOL_H
+# include <stdbool.h>
+#endif
+
+#ifndef __bool_true_false_are_defined
+# ifndef __cplusplus
+#  error :FIXME: You are the first one who use pre-C99 compiler.
+#  error :FIXME: Please add appropriate definition here.
+#  error :FIXME: This part is intentionally left undefined,
+#  error :FIXME: because the author no longer have such environment.
+# endif
+#endif
+
 #define LIKELY(x) RB_LIKELY(x)
 #define UNLIKELY(x) RB_UNLIKELY(x)