-# if defined __SUNPRO_C && (__SUNPRO_C < 0x550 || __STDC__ == 1)
- /* Avoid stupid "warning: _Bool is a keyword in ISO C99". */
-# define _Bool signed char
+typedef bool _Bool;
+# endif
+#else
+# if !defined __GNUC__
+ /* If @HAVE__BOOL@:
+ Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
+ the built-in _Bool type is used. See
+ http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
+ http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
+ http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
+ Similar bugs are likely with other compilers as well; this file
+ wouldn't be used if <stdbool.h> was working.
+ So we override the _Bool type.
+ If !@HAVE__BOOL@:
+ Need to define _Bool ourselves. As 'signed char' or as an enum type?
+ Use of a typedef, with SunPRO C, leads to a stupid
+ "warning: _Bool is a keyword in ISO C99".
+ Use of an enum type, with IRIX cc, leads to a stupid
+ "warning(1185): enumerated type mixed with another type".
+ The only benefit of the enum type, debuggability, is not important
+ with these compilers. So use 'signed char' and no typedef. */
+# define _Bool signed char