Cut down on extraneous "constant in conditional context" warnings when

lint encounters expressions like do { ... } while (0); and if (1) ...
We use these idioms frequently in our tree for scoping purposes and we
deem them to be safe.  Now lint will not warn if it encounters a constant
in a conditional context when the expression consists only of a constant
(with no operators) and the constant is 0 or 1.  This means that lint
will not warn for "if (1)" but will warn for "if (2)" and will also
continue to warn for "if (foo && 1)".  This cuts down the vast majority
of these warnings while still preserving the ability to catch bugs.

2 files changed, 15 insertions, 9 deletions

diff --git a/usr.bin/xlint/lint1/externs1.h b/usr.bin/xlint/lint1/externs1.h
index 0d7f2fe9a14..22e9e30a837 100644
--- a/usr.bin/xlint/lint1/externs1.h
+++ b/usr.bin/xlint/lint1/externs1.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: externs1.h,v 1.7 2005/12/10 18:42:45 cloder Exp $	*/
+/*	$OpenBSD: externs1.h,v 1.8 2005/12/12 23:35:59 cloder Exp $	*/
 /*	$NetBSD: externs1.h,v 1.7 1995/10/02 17:31:39 jpo Exp $	*/
 
 /*
@@ -205,6 +205,7 @@ extern	void	expr(tnode_t *, int, int);
 extern	void	chkmisc(tnode_t *, int, int, int, int, int, int);
 extern	int	conaddr(tnode_t *, sym_t **, ptrdiff_t *);
 extern	strg_t	*catstrg(strg_t *, strg_t *);
+extern	void	displexpr(tnode_t *, int);
 
 /*
  * func.c
diff --git a/usr.bin/xlint/lint1/tree.c b/usr.bin/xlint/lint1/tree.c
index 677ef807664..54b7c8545d4 100644
--- a/usr.bin/xlint/lint1/tree.c
+++ b/usr.bin/xlint/lint1/tree.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tree.c,v 1.22 2005/12/10 18:42:45 cloder Exp $	*/
+/*	$OpenBSD: tree.c,v 1.23 2005/12/12 23:35:59 cloder Exp $	*/
 /*	$NetBSD: tree.c,v 1.12 1995/10/02 17:37:57 jpo Exp $	*/
 
 /*
@@ -33,7 +33,7 @@
  */
 
 #ifndef lint
-static char rcsid[] = "$OpenBSD: tree.c,v 1.22 2005/12/10 18:42:45 cloder Exp $";
+static char rcsid[] = "$OpenBSD: tree.c,v 1.23 2005/12/12 23:35:59 cloder Exp $";
 #endif
 
 #include <stdlib.h>
@@ -79,7 +79,6 @@ static	tnode_t	*chkfarg(type_t *, tnode_t *);
 static	tnode_t	*parg(int, type_t *, tnode_t *);
 static	int	chkdbz(op_t, tnode_t *);
 static	void	nulleff(tnode_t *);
-static	void	displexpr(tnode_t *, int);
 static	void	chkaidx(tnode_t *, int);
 static	void	chkcomp(op_t, tnode_t *, tnode_t *);
 static	void	precconf(tnode_t *);
@@ -672,9 +671,10 @@ build(op_t op, tnode_t *ln, tnode_t *rn)
 	if (mp->m_tctx) {
 		if (ln->tn_op == CON ||
 		    ((mp->m_binary && op != QUEST) && rn->tn_op == CON)) {
-			if (hflag && !ccflg)
+			if (hflag && !ccflg) {
 				/* constant in conditional context */
 				warning(161);
+			}
 		}
 	}
 
@@ -3321,9 +3321,14 @@ expr(tnode_t *tn, int vctx, int tctx)
 			/* assignment in conditional context */
 			warning(159);
 	} else if (tn->tn_op == CON) {
-		if (hflag && tctx && !ccflg)
-			/* constant in conditional context */
-			warning(161);
+		if (hflag && tctx && !ccflg) {
+			if (isityp(tn->tn_type->t_tspec) &&
+			    tn->tn_val->v_quad != 0 &&
+			    tn->tn_val->v_quad != 1) {
+				/* constant in conditional context */
+				warning(161);
+			}
+		}
 	}
 	if (!modtab[tn->tn_op].m_sideeff) {
 		/*
@@ -3386,7 +3391,7 @@ nulleff(tnode_t *tn)
  * Dump an expression to stdout
  * only used for debugging
  */
-static void
+void
 displexpr(tnode_t *tn, int offs)
 {
 	u_quad_t uq;