Warn on empty non-compound selection statements, such as "if (foo);".

- "empty body of the if statement",
- "empty body of the else statement".

millert@ thought it's useful.

2 files changed, 40 insertions, 10 deletions

diff --git a/usr.bin/xlint/lint1/cgram.y b/usr.bin/xlint/lint1/cgram.y
index 19d5ae34346..5229ff64376 100644
--- a/usr.bin/xlint/lint1/cgram.y
+++ b/usr.bin/xlint/lint1/cgram.y
@@ -1,5 +1,5 @@
 %{
-/*	$OpenBSD: cgram.y,v 1.22 2007/09/08 17:49:18 cloder Exp $	*/
+/*	$OpenBSD: cgram.y,v 1.23 2011/05/31 22:00:07 martynas Exp $	*/
 /*	$NetBSD: cgram.y,v 1.8 1995/10/02 17:31:35 jpo Exp $	*/
 
 /*
@@ -34,7 +34,7 @@
  */
 
 #ifndef lint
-static char rcsid[] = "$OpenBSD: cgram.y,v 1.22 2007/09/08 17:49:18 cloder Exp $";
+static char rcsid[] = "$OpenBSD: cgram.y,v 1.23 2011/05/31 22:00:07 martynas Exp $";
 #endif
 
 #include <stdlib.h>
@@ -56,6 +56,11 @@ int	blklev;
  */
 int	mblklev;
 
+/*
+ * Is the statement empty?
+ */
+int	estmnt;
+
 static	int	toicon(tnode_t *);
 static	void	idecl(sym_t *, int);
 static	void	ignuptorp(void);
@@ -1181,15 +1186,26 @@ direct_abs_decl:
 	;
 
 stmnt:
-	  labeled_stmnt
+	  labeled_stmnt {
+		estmnt = 0;
+	  }
 	| expr_stmnt
-	| comp_stmnt
-	| selection_stmnt
-	| iteration_stmnt
+	| comp_stmnt {
+		estmnt = 0;
+	  }
+	| selection_stmnt {
+		estmnt = 0;
+	  }
+	| iteration_stmnt {
+		estmnt = 0;
+	  }
 	| jump_stmnt {
+		estmnt = 0;
 		ftflg = 0;
 	  }
-	| asm_stmnt
+	| asm_stmnt {
+		estmnt = 0;
+	  }
 	;
 
 labeled_stmnt:
@@ -1262,9 +1278,11 @@ stmnt_list:
 expr_stmnt:
 	  expr T_SEMI {
 		expr($1, 0, 0);
+		estmnt = 0;
 		ftflg = 0;
 	  }
 	| T_SEMI {
+		estmnt = 1;
 		ftflg = 0;
 	  }
 	;
@@ -1277,6 +1295,11 @@ selection_stmnt:
 	| if_without_else T_ELSE {
 		if2();
 	  } stmnt {
+		if (estmnt) {
+			/* empty body of the else statement */
+			warning(316);
+		}
+
 		if3(1);
 	  }
 	| if_without_else T_ELSE error {
@@ -1291,7 +1314,12 @@ selection_stmnt:
 	;
 
 if_without_else:
-	  if_expr stmnt
+	  if_expr stmnt {
+		if (estmnt) {
+			/* empty body of the if statement */
+			warning(315);
+		}
+	  }
 	| if_expr error
 	;
 
diff --git a/usr.bin/xlint/lint1/err.c b/usr.bin/xlint/lint1/err.c
index c2daa730e8c..a5ac6a31bdd 100644
--- a/usr.bin/xlint/lint1/err.c
+++ b/usr.bin/xlint/lint1/err.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: err.c,v 1.26 2006/06/02 17:38:59 cloder Exp $	*/
+/*	$OpenBSD: err.c,v 1.27 2011/05/31 22:00:07 martynas Exp $	*/
 /*	$NetBSD: err.c,v 1.8 1995/10/02 17:37:00 jpo Exp $	*/
 
 /*
@@ -33,7 +33,7 @@
  */
 
 #ifndef lint
-static char rcsid[] = "$OpenBSD: err.c,v 1.26 2006/06/02 17:38:59 cloder Exp $";
+static char rcsid[] = "$OpenBSD: err.c,v 1.27 2011/05/31 22:00:07 martynas Exp $";
 #endif
 
 /* number of errors found */
@@ -369,6 +369,8 @@ const	char *msgs[] = {
 	"suspicious operator for sizeof: %s",			      /* 312 */
 	"conversion of %s() return value from '%s' to '%s'",	      /* 313 */
 	"hexadecimal float constants are illegal in traditional C",   /* 314 */
+	"empty body of the if statement",			      /* 315 */
+	"empty body of the else statement",			      /* 316 */
 };
 
 /*