./:

	* c-common.c (c_common_truthvalue_conversion): When warning about
	using an assignment as a truth value, set TREE_NO_WARNING.
cp/:
	* 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.
testsuite/:
	* g++.dg/warn/Wparentheses-22.C: New test.
	* g++.dg/warn/Wparentheses-23.C: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@120348 138bc75d-0d04-0410-961f-82ee72b054a4

8 files changed, 281 insertions, 6 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 78b8ce8314c..30e9a20759a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2006-01-02  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.
+
 2007-01-02  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>
 
 	PR middle-end/7651
diff --git a/gcc/c-common.c b/gcc/c-common.c
index 0658141dadc..cca1490a9d5 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -1,6 +1,6 @@
 /* Subroutines shared by all languages that are variants of C.
    Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-   2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+   2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -2726,9 +2726,13 @@ c_common_truthvalue_conversion (tree expr)
       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:
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 16da3ee0aa1..abc7a71d7fc 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2006-01-02  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.
+
 2007-01-02  Douglas Gregor  <doug.gregor@gmail.com>
 
 	* pt.c (canonical_template_parms): Correct typo in comment.
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 41d2be9817c..5b8906eb020 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3,7 +3,7 @@
    building RTL.  These routines are used both during actual parsing
    and during the instantiation of template functions.
 
-   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
+   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
    Free Software Foundation, Inc.
    Written by Mark Mitchell (mmitchell@usa.net) based on code found
    formerly in parse.y and pt.c.
@@ -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);
 }
 
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 7e8b785b3eb..6c05b9fe1f1 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -1,6 +1,7 @@
 /* Build expressions with type checking for C++ compiler.
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
+   Free Software Foundation, Inc.
    Hacked by Michael Tiemann (tiemann@cygnus.com)
 
 This file is part of GCC.
@@ -6365,6 +6366,17 @@ convert_for_assignment (tree type, tree rhs,
 		 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);
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e2e3d3dbb05..5f17a946fe6 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-01-02  Ian Lance Taylor  <iant@google.com>
+
+	* g++.dg/warn/Wparentheses-22.C: New test.
+	* g++.dg/warn/Wparentheses-23.C: New test.
+
 2007-01-02  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>
 
 	PR middle-end/7651
diff --git a/gcc/testsuite/g++.dg/warn/Wparentheses-22.C b/gcc/testsuite/g++.dg/warn/Wparentheses-22.C
new file mode 100644
index 00000000000..395953dd446
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-22.C
@@ -0,0 +1,111 @@
+// { 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);
+  if (C(a))
+    foo (28);
+}
+
+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);
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wparentheses-23.C b/gcc/testsuite/g++.dg/warn/Wparentheses-23.C
new file mode 100644
index 00000000000..755c574d0f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-23.C
@@ -0,0 +1,121 @@
+// { 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);
+  if (C(a))
+    foo (28);
+}
+
+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);