Hi.
In current implementation we avoid giving "logical and/or of equal
expressions" warning for literal constant operands. The attached patch
fixes the check to make it treat const-qualified VAR_DECLs with constant
initializers the same way.
Bootstrapped and regtested on x86_64-linux. OK for trunk?
--
Regards,
Mikhail Maltsev
gcc/c-family/ChangeLog:
2015-06-19 Mikhail Maltsev <malts...@gmail.com>
PR c++/66572
* c-common.c (warn_logical_operator): Treat constant-initialized
VAR_DECLs like literal constants.
gcc/testsuite/ChangeLog:
2015-06-19 Mikhail Maltsev <malts...@gmail.com>
PR c++/66572
* c-c++-common/Wlogical-op-2.c: New test.
* g++.dg/warn/Wlogical-op-2.C: New test.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index dc2bf00..38c7be9 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -1766,9 +1766,12 @@ warn_logical_operator (location_t location, enum tree_code code, tree type,
return;
}
- /* We do not warn for constants because they are typical of macro
- expansions that test for features. */
- if (CONSTANT_CLASS_P (op_left) || CONSTANT_CLASS_P (op_right))
+ /* We do not warn for literal constants because they are typical of macro
+ expansions that test for features. Likewise, we do not warn for
+ const-qualified and constexpr variables which are initialized by constant
+ expressions, because they can come from e.g. <type_traits> or similar user
+ code. */
+ if (TREE_CONSTANT (op_left) || TREE_CONSTANT (op_right))
return;
/* This warning only makes sense with logical operands. */
diff --git a/gcc/testsuite/c-c++-common/Wlogical-op-2.c b/gcc/testsuite/c-c++-common/Wlogical-op-2.c
new file mode 100644
index 0000000..47f5c28
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wlogical-op-2.c
@@ -0,0 +1,24 @@
+/* PR c++/66572 */
+/* { dg-do compile } */
+/* { dg-options "-Wlogical-op" } */
+
+#ifndef __cplusplus
+# define bool _Bool
+# define true 1
+# define false 0
+#endif
+
+void
+no_warn ()
+{
+ const bool cst_a = true;
+ const bool cst_b = false;
+
+ if (cst_a || cst_b) {}
+ if (cst_a && cst_b) {}
+ if (true && cst_a) {}
+ if (true || cst_a) {}
+ if (false && cst_a) {}
+ if (false || cst_a) {}
+}
+
diff --git a/gcc/testsuite/g++.dg/warn/Wlogical-op-2.C b/gcc/testsuite/g++.dg/warn/Wlogical-op-2.C
new file mode 100644
index 0000000..252592c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wlogical-op-2.C
@@ -0,0 +1,59 @@
+// PR c++/66572
+// { dg-do compile }
+// { dg-options "-Wlogical-op" }
+
+#if __cplusplus >= 201103L
+# define CONSTEXPR constexpr
+#else
+# define CONSTEXPR const
+#endif
+
+struct true_type
+{
+ static CONSTEXPR bool value = true;
+};
+
+struct false_type
+{
+ static CONSTEXPR bool value = true;
+};
+
+template<typename T>
+struct is_unsigned : false_type { };
+
+template<>
+struct is_unsigned<unsigned int> : true_type { };
+
+template<typename T1, typename T2>
+bool both_are_unsigned ()
+{
+ return is_unsigned <T1>::value && is_unsigned <T2>::value;
+}
+
+template<typename T1, typename T2>
+bool one_of_is_unsigned ()
+{
+ return is_unsigned <T1>::value || is_unsigned <T2>::value;
+}
+
+void
+foo ()
+{
+ both_are_unsigned <unsigned int, unsigned int> ();
+ both_are_unsigned <int, unsigned int> ();
+ both_are_unsigned <int, int> ();
+ one_of_is_unsigned <unsigned int, unsigned int> ();
+ one_of_is_unsigned <int, unsigned int> ();
+ one_of_is_unsigned <int, int> ();
+}
+
+void
+bar (const int parm_a)
+{
+ const bool a = parm_a;
+ if (a && a) {} /* { dg-warning "logical .and. of equal expressions" } */
+ if (a || a) {} /* { dg-warning "logical .or. of equal expressions" } */
+ if (parm_a && parm_a) {} /* { dg-warning "logical .and. of equal expressions" } */
+ if (parm_a || parm_a) {} /* { dg-warning "logical .or. of equal expressions" } */
+}
+
