PR c/49706

	* doc/invoke.texi: Document -Wlogical-not-parentheses.
c-family/
	* c-common.c (warn_logical_not_parentheses): New function.
	* c-common.h (warn_logical_not_parentheses): Declare.
	* c.opt (Wlogical-not-parentheses): New option.
c/
	* c-typeck.c (parser_build_binary_op): Warn when logical not is used
	on the left hand side operand of a comparison. 
cp/
	* parser.c (cp_parser_binary_expression): Warn when logical not is
	used on the left hand side operand of a comparison.
testsuite/
	* c-c++-common/pr49706.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@211255 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 36 insertions, 0 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index c6a041a037e..07bcdab2e4c 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,10 @@
+2014-06-05  Marek Polacek  <polacek@redhat.com>
+
+	PR c/49706
+	* c-common.c (warn_logical_not_parentheses): New function.
+	* c-common.h (warn_logical_not_parentheses): Declare.
+	* c.opt (Wlogical-not-parentheses): New option.
+
 2014-06-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c/30020
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 07a17981642..fb6c61204c3 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -1722,6 +1722,29 @@ warn_logical_operator (location_t location, enum tree_code code, tree type,
     }
 }
 
+/* Warn about logical not used on the left hand side operand of a comparison.
+   This function assumes that the LHS is inside of TRUTH_NOT_EXPR.
+   Do not warn if the LHS or RHS is of a boolean or a vector type.  */
+
+void
+warn_logical_not_parentheses (location_t location, enum tree_code code,
+			      tree lhs, tree rhs)
+{
+  if (TREE_CODE_CLASS (code) != tcc_comparison)
+    return;
+  if (TREE_TYPE (lhs) == NULL_TREE
+      || TREE_TYPE (rhs) == NULL_TREE)
+    ;
+  else if (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE
+	   || TREE_CODE (TREE_TYPE (rhs)) == BOOLEAN_TYPE
+	   || VECTOR_TYPE_P (TREE_TYPE (lhs))
+	   || VECTOR_TYPE_P (TREE_TYPE (rhs)))
+    return;
+
+  warning_at (location, OPT_Wlogical_not_parentheses,
+	      "logical not is only applied to the left hand side of "
+	      "comparison");
+}
 
 /* Warn if EXP contains any computations whose results are not used.
    Return true if a warning is printed; false otherwise.  LOCUS is the
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 0d34004e4ff..83d5dee30e0 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -772,6 +772,8 @@ extern void overflow_warning (location_t, tree);
 extern bool warn_if_unused_value (const_tree, location_t);
 extern void warn_logical_operator (location_t, enum tree_code, tree,
 				   enum tree_code, tree, enum tree_code, tree);
+extern void warn_logical_not_parentheses (location_t, enum tree_code, tree,
+					  tree);
 extern void check_main_parameter_types (tree decl);
 extern bool c_determine_visibility (tree);
 extern bool vector_types_compatible_elements_p (tree, tree);
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 5d36a80408d..76e67d78ac7 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -490,6 +490,10 @@ Wlogical-op
 C ObjC C++ ObjC++ Var(warn_logical_op) Init(0) Warning 
 Warn when a logical operator is suspiciously always evaluating to true or false
 
+Wlogical-not-parentheses
+C ObjC C++ ObjC++ Var(warn_logical_not_paren) Warning
+Warn when logical not is used on the left hand side operand of a comparison
+
 Wlong-long
 C ObjC C++ ObjC++ Var(warn_long_long) Init(-1) Warning
 Do not warn about using \"long long\" when -pedantic