Use stdbool.h if suitable

Using the standard bool type provided by C allows some recent compilers
and debuggers to give better diagnostics.  Also, some extension code and
third-party headers are increasingly pulling in stdbool.h, so it's
probably saner if everyone uses the same definition.

But PostgreSQL code is not prepared to handle bool of a size other than
1, so we keep our own old definition if we encounter a stdbool.h with a
bool of a different size.  (Among current build farm members, this only
applies to old macOS versions on PowerPC.)

To check that the used bool is of the right size, add a static
assertions about size of GinTernaryValue vs bool.  This is currently the
only place that assumes that bool and char are of the same size.

Discussion: https://www.postgresql.org/message-id/flat/[email protected]

1 files changed, 12 insertions, 2 deletions

diff --git a/src/include/c.h b/src/include/c.h
index 37c0c391990..107f4f6bcd7 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -255,12 +255,21 @@
  * bool
  *		Boolean value, either true or false.
  *
- * XXX for C++ compilers, we assume the compiler has a compatible
- * built-in definition of bool.
+ * Use stdbool.h if available and its bool has size 1.  That's useful for
+ * better compiler and debugger output and for compatibility with third-party
+ * libraries.  But PostgreSQL currently cannot deal with bool of other sizes;
+ * there are static assertions around the code to prevent that.
+ *
+ * For C++ compilers, we assume the compiler has a compatible built-in
+ * definition of bool.
  */
 
 #ifndef __cplusplus
 
+#if defined(HAVE_STDBOOL_H) && SIZEOF_BOOL == 1
+#include <stdbool.h>
+#else
+
 #ifndef bool
 typedef char bool;
 #endif
@@ -273,6 +282,7 @@ typedef char bool;
 #define false	((bool) 0)
 #endif
 
+#endif
 #endif							/* not C++ */