Wed Sep 2 23:42:58 2020 UTC ()

make(1): document the value restrictions for Boolean variables

The previous lenient rule came from the sprite.h header that was not
specific to make.  To avoid confusion, only the expected values should
be stored in a Boolean variable.  To help find obvious violations and
inconsistencies, there are different possibilities for the Boolean type,
during development.

In C there is no way to actually enforce this restriction at runtime.
It would be possible in C++, but the code is not ready to be compiled
with a C++ compiler.


(rillig)

diff -r1.136 -r1.137 src/usr.bin/make/make.h

--- src/usr.bin/make/make.h 2020/09/02 04:08:54	1.136
+++ src/usr.bin/make/make.h 2020/09/02 23:42:58	1.137

 @@ -1,14 +1,14 @@
-/*	$NetBSD: make.h,v 1.136 2020/09/02 04:08:54 rillig Exp $	*/
+/*	$NetBSD: make.h,v 1.137 2020/09/02 23:42:58 rillig Exp $	*/
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
+ *
  * This code is derived from software contributed to Berkeley by
  * Adam de Boor.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -120,39 +120,41 @@
 #define	MAKE_ATTR_DEAD		__volatile
 #else
 #define	MAKE_ATTR_DEAD		/* delete */
 #endif
 #if MAKE_GNUC_PREREQ(2, 7)
 #define MAKE_ATTR_PRINTFLIKE(fmtarg, firstvararg)	\
 	    __attribute__((__format__ (__printf__, fmtarg, firstvararg)))
 #else
 #define MAKE_ATTR_PRINTFLIKE(fmtarg, firstvararg)	/* delete */
 #endif
 /*
- * A boolean type is defined as an integer, not an enum. This allows a
+ * A boolean type is defined as an integer, not an enum, for historic reasons.
- * boolean argument to be an expression that isn't strictly 0 or 1 valued.
+ * The only allowed values are the constants TRUE and FALSE (1 and 0).
  */
 #ifdef USE_DOUBLE_BOOLEAN
 /* During development, to find type mismatches in function declarations. */
 typedef double Boolean;
 #elif defined(USE_UCHAR_BOOLEAN)
 /* During development, to find code that depends on the exact value of TRUE or
  * that stores other values in Boolean variables. */
 typedef unsigned char Boolean;
 #define TRUE ((unsigned char)0xFF)
 #define FALSE ((unsigned char)0x00)
 #elif defined(USE_ENUM_BOOLEAN)
 typedef enum { FALSE, TRUE} Boolean;
 #else
 typedef int Boolean;
 #endif
 #ifndef TRUE
 #define TRUE	1
 #endif /* TRUE */
 #ifndef FALSE
 #define FALSE	0
 #endif /* FALSE */
 #include "lst.h"
 #include "enum.h"
 #include "hash.h"