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PATCH RFA: More -Wparentheses checks for C++
- From: Ian Lance Taylor <iant at google dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: 28 Dec 2006 14:26:06 -0800
- Subject: PATCH RFA: More -Wparentheses checks for C++
In my earlier patch adding support for -Wparentheses to the C++
frontend, I forgot about the case of a class with a conversion to
bool. Assignments of instances of such a class do not follow the
c_common_truthvalue_conversion path used by assignments of builtin
types.
This patch adds support for this. It adds -Wparentheses warnings for
bool b = a = b;
bool fn(C a, C b) { return a = b; }
where a and b have class type. These warnings already exist when a
and b are builtin types.
Tested with a C/C++ bootstrap and gcc/libstdc++-v3 testsuite run on
i686-pc-linux-gnu.
OK for mainline?
Ian
gcc/ChangeLog:
2006-12-28 Ian Lance Taylor <iant@google.com>
* c-common.c (c_common_truthvalue_conversion): When warning about
using an assignment as a truth value, set TREE_NO_WARNING.
gcc/cp/ChangeLog:
2006-12-28 Ian Lance Taylor <iant@google.com>
* semantics.c (maybe_convert_cond): Optionally warn when using an
assignment as a condition.
* typeck.c (convert_for_assignment): Optionally warn about
assigning the result of an assignment to a bool.
gcc/testsuite/ChangeLog:
2006-12-28 Ian Lance Taylor <iant@google.com>
* g++.dg/warn/Wparentheses-22.C: New test.
* g++.dg/warn/Wparentheses-23.C: New test.
Index: gcc/cp/typeck.c
===================================================================
--- gcc/cp/typeck.c (revision 120236)
+++ gcc/cp/typeck.c (working copy)
@@ -6306,6 +6306,17 @@ convert_for_assignment (tree type, tree
errtype);
}
+ /* If -Wparentheses, warn about a = b = c when a has type bool. */
+ if (warn_parentheses
+ && type == boolean_type_node
+ && TREE_CODE (rhs) == MODIFY_EXPR
+ && !TREE_NO_WARNING (rhs))
+ {
+ warning (OPT_Wparentheses,
+ "suggest parentheses around assignment used as truth value");
+ TREE_NO_WARNING (rhs) = 1;
+ }
+
return perform_implicit_conversion (strip_top_quals (type), rhs);
}
Index: gcc/cp/semantics.c
===================================================================
--- gcc/cp/semantics.c (revision 120236)
+++ gcc/cp/semantics.c (working copy)
@@ -587,6 +587,16 @@ maybe_convert_cond (tree cond)
/* Do the conversion. */
cond = convert_from_reference (cond);
+
+ if (TREE_CODE (cond) == MODIFY_EXPR
+ && !TREE_NO_WARNING (cond)
+ && warn_parentheses)
+ {
+ warning (OPT_Wparentheses,
+ "suggest parentheses around assignment used as truth value");
+ TREE_NO_WARNING (cond) = 1;
+ }
+
return condition_conversion (cond);
}
Index: gcc/c-common.c
===================================================================
--- gcc/c-common.c (revision 120236)
+++ gcc/c-common.c (working copy)
@@ -2726,9 +2726,13 @@ c_common_truthvalue_conversion (tree exp
break;
case MODIFY_EXPR:
- if (!TREE_NO_WARNING (expr))
- warning (OPT_Wparentheses,
- "suggest parentheses around assignment used as truth value");
+ if (!TREE_NO_WARNING (expr)
+ && warn_parentheses)
+ {
+ warning (OPT_Wparentheses,
+ "suggest parentheses around assignment used as truth value");
+ TREE_NO_WARNING (expr) = 1;
+ }
break;
default:
Index: gcc/testsuite/g++.dg/warn/Wparentheses-22.C
===================================================================
--- gcc/testsuite/g++.dg/warn/Wparentheses-22.C (revision 0)
+++ gcc/testsuite/g++.dg/warn/Wparentheses-22.C (revision 0)
@@ -0,0 +1,109 @@
+// { dg-do compile }
+// { dg-options "-Wparentheses" }
+
+// Warnings for assignments used as truth-values when using classes.
+// Like Wparentheses-1.C, but with a class.
+
+int foo (int);
+
+class C
+{
+ public:
+ C()
+ : b(0)
+ { }
+
+ // Use default assignment constructor.
+
+ // Provide conversion to bool so that an instance of this class will
+ // work as a condition.
+ operator bool() const
+ { return b != 0; }
+
+ private:
+ int b;
+};
+
+C a, b, c;
+bool d;
+
+void
+bar (void)
+{
+ if (a = b) // { dg-warning "assignment" "correct warning" }
+ foo (0);
+ if ((a = b))
+ foo (1);
+ if (a = a) // { dg-warning "assignment" "correct warning" }
+ foo (2);
+ if ((a = a))
+ foo (3);
+ if (b = c) // { dg-warning "assignment" "correct warning" }
+ foo (4);
+ else
+ foo (5);
+ if ((b = c))
+ foo (6);
+ else
+ foo (7);
+ if (b = b) // { dg-warning "assignment" "correct warning" }
+ foo (8);
+ else
+ foo (9);
+ if ((b = b))
+ foo (10);
+ else
+ foo (11);
+ while (c = b) // { dg-warning "assignment" "correct warning" }
+ foo (12);
+ while ((c = b))
+ foo (13);
+ while (c = c) // { dg-warning "assignment" "correct warning" }
+ foo (14);
+ while ((c = c))
+ foo (15);
+ do foo (16); while (a = b); // { dg-warning "assignment" "correct warning" }
+ do foo (17); while ((a = b));
+ do foo (18); while (a = a); // { dg-warning "assignment" "correct warning" }
+ do foo (19); while ((a = a));
+ for (;c = b;) // { dg-warning "assignment" "correct warning" }
+ foo (20);
+ for (;(c = b);)
+ foo (21);
+ for (;c = c;) // { dg-warning "assignment" "correct warning" }
+ foo (22);
+ for (;(c = c);)
+ foo (23);
+ d = a = b; // { dg-warning "assignment" "correct warning" }
+ foo (24);
+ d = (a = b);
+ foo (25);
+ d = a = a; // { dg-warning "assignment" "correct warning" }
+ foo (26);
+ d = (a = a);
+ foo (27);
+}
+
+bool
+bar1 (void)
+{
+ return a = b; // { dg-warning "assignment" "correct warning" }
+}
+
+bool
+bar2 (void)
+{
+ return (a = b);
+}
+
+bool
+bar3 (void)
+{
+ return a = a; // { dg-warning "assignment" "correct warning" }
+}
+
+bool
+bar4 (void)
+{
+ return (a = a);
+}
Index: gcc/testsuite/g++.dg/warn/Wparentheses-23.C
===================================================================
--- gcc/testsuite/g++.dg/warn/Wparentheses-23.C (revision 0)
+++ gcc/testsuite/g++.dg/warn/Wparentheses-23.C (revision 0)
@@ -0,0 +1,117 @@
+// { dg-do compile }
+// { dg-options "-Wparentheses" }
+
+// Template version of Wparentheses-22.C.
+
+int foo (int);
+
+class C
+{
+ public:
+ C()
+ : b(0)
+ { }
+
+ // Use default assignment constructor.
+
+ // Provide conversion to bool so that an instance of this class will
+ // work as a condition.
+ operator bool() const
+ { return b != 0; }
+
+ private:
+ int b;
+};
+
+C a, b, c;
+bool d;
+
+template<class T>
+void
+bar (T)
+{
+ if (a = b) // { dg-warning "assignment" "correct warning" }
+ foo (0);
+ if ((a = b))
+ foo (1);
+ if (a = a) // { dg-warning "assignment" "correct warning" }
+ foo (2);
+ if ((a = a))
+ foo (3);
+ if (b = c) // { dg-warning "assignment" "correct warning" }
+ foo (4);
+ else
+ foo (5);
+ if ((b = c))
+ foo (6);
+ else
+ foo (7);
+ if (b = b) // { dg-warning "assignment" "correct warning" }
+ foo (8);
+ else
+ foo (9);
+ if ((b = b))
+ foo (10);
+ else
+ foo (11);
+ while (c = b) // { dg-warning "assignment" "correct warning" }
+ foo (12);
+ while ((c = b))
+ foo (13);
+ while (c = c) // { dg-warning "assignment" "correct warning" }
+ foo (14);
+ while ((c = c))
+ foo (15);
+ do foo (16); while (a = b); // { dg-warning "assignment" "correct warning" }
+ do foo (17); while ((a = b));
+ do foo (18); while (a = a); // { dg-warning "assignment" "correct warning" }
+ do foo (19); while ((a = a));
+ for (;c = b;) // { dg-warning "assignment" "correct warning" }
+ foo (20);
+ for (;(c = b);)
+ foo (21);
+ for (;c = c;) // { dg-warning "assignment" "correct warning" }
+ foo (22);
+ for (;(c = c);)
+ foo (23);
+ d = a = b; // { dg-warning "assignment" "correct warning" }
+ foo (24);
+ d = (a = b);
+ foo (25);
+ d = a = a; // { dg-warning "assignment" "correct warning" }
+ foo (26);
+ d = (a = a);
+ foo (27);
+}
+
+template<class T>
+bool
+bar1 (T)
+{
+ return a = b; // { dg-warning "assignment" "correct warning" }
+}
+
+template<class T>
+bool
+bar2 (T)
+{
+ return (a = b);
+}
+
+template<class T>
+bool
+bar3 (T)
+{
+ return a = a; // { dg-warning "assignment" "correct warning" }
+}
+
+template<class T>
+bool
+bar4 (T)
+{
+ return (a = a);
+}
+
+template void bar<int> (int); // { dg-warning "instantiated" }
+template bool bar1<int> (int); // { dg-warning "instantiated" }
+template bool bar2<int> (int);
+template bool bar3<int> (int); // { dg-warning "instantiated" }
+template bool bar4<int> (int);