On Fri, Aug 26, 2016 at 11:18:46AM +0200, Richard Biener wrote:
> On Fri, Aug 26, 2016 at 10:57 AM, Marek Polacek <pola...@redhat.com> wrote:
> > On Fri, Aug 26, 2016 at 10:53:01AM +0200, Richard Biener wrote:
> >> On Thu, Aug 25, 2016 at 3:39 PM, Marek Polacek <pola...@redhat.com> wrote:
> >> > On Thu, Aug 25, 2016 at 11:17:37AM +0200, Richard Biener wrote:
> >> >> On Wed, Aug 24, 2016 at 7:43 PM, Marek Polacek <pola...@redhat.com>
> >> >> wrote:
> >> >> > The -Wlogical-not-parentheses deliberately doesn't warn when the RHS
> >> >> > has
> >> >> > boolean type. But since in C the type of a comparison is int, we need
> >> >> > to check for tcc_comparison, too.
> >> >> >
> >> >> > Bootstrapped/regtested on x86_64-linux and ppc64le-redhat-linux, ok
> >> >> > for trunk?
> >> >>
> >> >> What about using truth_value_p ()? That also includes && and || (just
> >> >> in case those
> >> >> do not have boolean type).
> >> >
> >> > You're right that I should also handle || and && (done in this patch).
> >> > But I
> >> > can't use truth_value_p because we want to warn for e.g. "!a == (a & b)".
> >>
> >> But a & b isn't truth_value_p. a && b is. Do we want to warn about
> >> !a == (a && b)?
> >
> > We don't want to warn about !a == (a && b), I think. But truth_value_p
> > returns
> > true for both TRUTH_AND_EXPR and TRUTH_ANDIF_EXPR. I find that confusing,
> > and
> > I can't use it in the current form because of that.
>
> Note that a & b would be BIT_AND_EXPR, TRUTH_AND_EXPR is just
> non-short-circuiting
> &&
Ugh, not sure what went wrong. Let's pretend this never happened.
And now the patch for real:
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2016-08-26 Marek Polacek <pola...@redhat.com>
PR c/77292
* c-common.c (warn_logical_not_parentheses): Don't warn for
a comparison or a logical operator.
* c-c++-common/Wlogical-not-parentheses-1.c: New test.
diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index 001070d..f9b7c3c 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -1481,7 +1481,8 @@ warn_tautological_cmp (location_t loc, enum tree_code
code, tree lhs, tree rhs)
/* 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 RHS is of a boolean type. */
+ Do not warn if RHS is of a boolean type, a logical operator, or
+ a comparison. */
void
warn_logical_not_parentheses (location_t location, enum tree_code code,
@@ -1489,7 +1490,8 @@ warn_logical_not_parentheses (location_t location, enum
tree_code code,
{
if (TREE_CODE_CLASS (code) != tcc_comparison
|| TREE_TYPE (rhs) == NULL_TREE
- || TREE_CODE (TREE_TYPE (rhs)) == BOOLEAN_TYPE)
+ || TREE_CODE (TREE_TYPE (rhs)) == BOOLEAN_TYPE
+ || truth_value_p (TREE_CODE (rhs)))
return;
/* Don't warn for !x == 0 or !y != 0, those are equivalent to
diff --git gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c
gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c
index e69de29..b6b4e9d 100644
--- gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c
+++ gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c
@@ -0,0 +1,26 @@
+/* PR c/77292 */
+/* { dg-do compile } */
+/* { dg-options "-Wlogical-not-parentheses" } */
+
+ /* Test that we don't warn if rhs is a comparison or a logical op. */
+
+int
+foo (int a, int b)
+{
+ int r = 0;
+ r += !a == (a < b);
+ r += !a == (a > b);
+ r += !a == (a >= b);
+ r += !a == (a <= b);
+ r += !a == (a != b);
+ r += !a == (a == b);
+ r += !a == (a || b);
+ r += !a == (a && b);
+ r += !a == (!b);
+
+ r += !a == (a ^ b); /* { dg-warning "logical not is only applied to the left
hand side of comparison" } */
+ r += !a == (a | b); /* { dg-warning "logical not is only applied to the left
hand side of comparison" } */
+ r += !a == (a & b); /* { dg-warning "logical not is only applied to the left
hand side of comparison" } */
+
+ return r;
+}
Marek
