Re: [C PATCH] Improve locinfo a bit (PR c/59846)

[Marek Polacek <polacek at redhat dot com>]

On Thu, Jan 23, 2014 at 05:50:23PM +0000, Joseph S. Myers wrote:
> On Thu, 23 Jan 2014, Marek Polacek wrote:
> 
> > shorten_compare can produce a better locinfo if we pass location
> > from {,cp_}build_binary_op to it; op0/op1 there don't have location.
> > Furthermore, I see no reason why use input_location in
> > parser_build_binary_op when we can use more accurate location.
> > 
> > I don't know if/how I can test the column info using dejagnu, so
> > no testcase attached.  But to give you an idea, instead of
> 
> The approach used is
> 
> /* { dg-warning "14:comparison is always false" } */
> 
> or similar, with the column number put at the start of the dg-error / 
> dg-warning text.

Argh, not sure how I missed that.  So with a testcase this time.

OK now?

2014-01-23  Marek Polacek  <polacek@redhat.com>

	PR c/59846
c-family/
	* c-common.c (shorten_compare): Add location_t parameter.
	* c-common.h (shorten_binary_op): Adjust declaration.
cp/
	* typeck.c (cp_build_binary_op): Pass location to shorten_compare.
c/
	* c-typeck.c (parser_build_binary_op): Use location instead of
	input_location.
	(build_binary_op): Pass location to shorten_compare.
testsuite/
	* gcc.dg/pr59846.c: New test.

--- gcc/c-family/c-common.h.mp	2014-01-23 16:19:49.936114468 +0100
+++ gcc/c-family/c-common.h	2014-01-23 19:31:26.276522298 +0100
@@ -799,7 +799,8 @@ extern tree shorten_binary_op (tree resu
 /* Subroutine of build_binary_op, used for comparison operations.
    See if the operands have both been converted from subword integer types
    and, if so, perhaps change them both back to their original type.  */
-extern tree shorten_compare (tree *, tree *, tree *, enum tree_code *);
+extern tree shorten_compare (location_t, tree *, tree *, tree *,
+			     enum tree_code *);
 
 extern tree pointer_int_sum (location_t, enum tree_code, tree, tree,
 			     bool = true);
--- gcc/c-family/c-common.c.mp	2014-01-23 16:19:49.935114463 +0100
+++ gcc/c-family/c-common.c	2014-01-23 19:31:26.279522313 +0100
@@ -3974,13 +3974,15 @@ expr_original_type (tree expr)
    of build_binary_op: OP0_PTR is &OP0, OP1_PTR is &OP1,
    RESTYPE_PTR is &RESULT_TYPE and RESCODE_PTR is &RESULTCODE.
 
+   LOC is the location of the comparison.
+
    If this function returns nonzero, it means that the comparison has
    a constant value.  What this function returns is an expression for
    that value.  */
 
 tree
-shorten_compare (tree *op0_ptr, tree *op1_ptr, tree *restype_ptr,
-		 enum tree_code *rescode_ptr)
+shorten_compare (location_t loc, tree *op0_ptr, tree *op1_ptr,
+		 tree *restype_ptr, enum tree_code *rescode_ptr)
 {
   tree type;
   tree op0 = *op0_ptr;
@@ -3989,7 +3991,6 @@ shorten_compare (tree *op0_ptr, tree *op
   int real1, real2;
   tree primop0, primop1;
   enum tree_code code = *rescode_ptr;
-  location_t loc = EXPR_LOC_OR_LOC (op0, input_location);
 
   /* Throw away any conversions to wider types
      already present in the operands.  */
--- gcc/cp/typeck.c.mp	2014-01-23 16:19:49.939114483 +0100
+++ gcc/cp/typeck.c	2014-01-23 19:31:26.312522476 +0100
@@ -4838,7 +4838,8 @@ cp_build_binary_op (location_t location,
 	  tree xop0 = op0, xop1 = op1, xresult_type = result_type;
 	  enum tree_code xresultcode = resultcode;
 	  tree val
-	    = shorten_compare (&xop0, &xop1, &xresult_type, &xresultcode);
+	    = shorten_compare (location, &xop0, &xop1, &xresult_type,
+			       &xresultcode);
 	  if (val != 0)
 	    return cp_convert (boolean_type_node, val, complain);
 	  op0 = xop0, op1 = xop1;
--- gcc/c/c-typeck.c.mp	2014-01-23 19:30:54.392378861 +0100
+++ gcc/c/c-typeck.c	2014-01-23 19:31:26.324522535 +0100
@@ -3388,11 +3388,11 @@ parser_build_binary_op (location_t locat
   /* Check for cases such as x+y<<z which users are likely
      to misinterpret.  */
   if (warn_parentheses)
-    warn_about_parentheses (input_location, code,
-			    code1, arg1.value, code2, arg2.value);
+    warn_about_parentheses (location, code, code1, arg1.value, code2,
+			    arg2.value);
 
   if (warn_logical_op)
-    warn_logical_operator (input_location, code, TREE_TYPE (result.value),
+    warn_logical_operator (location, code, TREE_TYPE (result.value),
 			   code1, arg1.value, code2, arg2.value);
 
   /* Warn about comparisons against string literals, with the exception
@@ -10854,7 +10854,8 @@ build_binary_op (location_t location, en
 	  tree xop0 = op0, xop1 = op1, xresult_type = result_type;
 	  enum tree_code xresultcode = resultcode;
 	  tree val
-	    = shorten_compare (&xop0, &xop1, &xresult_type, &xresultcode);
+	    = shorten_compare (location, &xop0, &xop1, &xresult_type,
+			       &xresultcode);
 
 	  if (val != 0)
 	    {
--- gcc/testsuite/gcc.dg/pr59846.c.mp	2014-01-23 19:34:32.790368466 +0100
+++ gcc/testsuite/gcc.dg/pr59846.c	2014-01-23 19:42:00.910793437 +0100
@@ -0,0 +1,39 @@
+/* PR c/59846 */
+/* { dg-do compile } */
+/* { dg-options "-Wlogical-op -Wtype-limits" } */
+
+_Bool
+fn1 (unsigned int p)
+{
+  return 0UL > p; /* { dg-warning "14:comparison is always false due to limited range of data type" } */
+}
+
+_Bool
+fn2 (unsigned int p)
+{
+  return 0UL <= p; /* { dg-warning "14:comparison is always true due to limited range of data type" } */
+}
+
+_Bool
+fn3 (unsigned int p)
+{
+  return p >= 0U; /* { dg-warning "12:comparison of unsigned expression >= 0 is always true" } */
+}
+
+_Bool
+fn4 (unsigned int p)
+{
+  return p < 0U; /* { dg-warning "12:comparison of unsigned expression < 0 is always false" } */
+}
+
+_Bool
+fn5 (_Bool p)
+{
+  return p || !p; /* { dg-warning "12:logical" } */
+}
+
+_Bool
+fn6 (_Bool p)
+{
+  return p && !p; /* { dg-warning "12:logical" } */
+}

	Marek