DR 1423 PR c++/52174

gcc/cp
2014-06-03  Paolo Carlini  <paolo.carlini@oracle.com>

	DR 1423
	PR c++/52174
	* call.c (standard_conversion): Convert nullptr to bool only
	in case of direct-initialization.
	(convert_like_real): Provide informative error message.

gcc/testsuite
2014-06-03  Paolo Carlini  <paolo.carlini@oracle.com>

	DR 1423
	PR c++/52174
	* g++.dg/cpp0x/nullptr31.C: New.
	* g++.dg/cpp0x/sfinae-nullptr1.C: Likewise.
	* g++.dg/cpp0x/nullptr17.C: Update.

libstdc++-v3
2014-06-03  Paolo Carlini  <paolo.carlini@oracle.com>

	DR 1423
	PR c++/52174
	* testsuite/20_util/is_assignable/value.cc: Update.

From-SVN: r211195

6 files changed, 63 insertions, 7 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2fa1549f..9a22842 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2014-06-03  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	DR 1423
+	PR c++/52174
+	* call.c (standard_conversion): Convert nullptr to bool only
+	in case of direct-initialization.
+	(convert_like_real): Provide informative error message.
+
 2014-06-03  Marek Polacek  <polacek@redhat.com>
 
 	PR c/60439
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index b60bab7..75a6a4a 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -1311,10 +1311,10 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
     {
       /* [conv.bool]
 
-	  An rvalue of arithmetic, unscoped enumeration, pointer, or
-	  pointer to member type can be converted to an rvalue of type
-	  bool. ... An rvalue of type std::nullptr_t can be converted
-	  to an rvalue of type bool;  */
+	  A prvalue of arithmetic, unscoped enumeration, pointer, or pointer
+	  to member type can be converted to a prvalue of type bool. ...
+	  For direct-initialization (8.5 [dcl.init]), a prvalue of type
+	  std::nullptr_t can be converted to a prvalue of type bool;  */
       if (ARITHMETIC_TYPE_P (from)
 	  || UNSCOPED_ENUM_P (from)
 	  || fcode == POINTER_TYPE
@@ -1328,6 +1328,8 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
 		  && conv->rank < cr_pbool)
 	      || NULLPTR_TYPE_P (from))
 	    conv->rank = cr_pbool;
+	  if (NULLPTR_TYPE_P (from) && (flags & LOOKUP_ONLYCONVERTING))
+	    conv->bad_p = true;
 	  return conv;
 	}
 
@@ -6062,6 +6064,14 @@ convert_like_real (conversion *convs, tree expr, tree fn, int argnum,
 	    expr = CONSTRUCTOR_ELT (expr, 0)->value;
 	}
 
+      /* Give a helpful error if this is bad because a conversion to bool
+	 from std::nullptr_t requires direct-initialization.  */
+      if (NULLPTR_TYPE_P (TREE_TYPE (expr))
+	  && TREE_CODE (totype) == BOOLEAN_TYPE)
+	complained = permerror (loc, "converting to %qT from %qT requires "
+				"direct-initialization",
+				totype, TREE_TYPE (expr));
+
       for (; t ; t = next_conversion (t))
 	{
 	  if (t->kind == ck_user && t->cand->reason)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c409d99..d3af148 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2014-06-03  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	DR 1423
+	PR c++/52174
+	* g++.dg/cpp0x/nullptr31.C: New.
+	* g++.dg/cpp0x/sfinae-nullptr1.C: Likewise.
+	* g++.dg/cpp0x/nullptr17.C: Update.
+
 2014-06-03  Marek Polacek  <polacek@redhat.com>
 
 	PR c/60439
diff --git a/gcc/testsuite/g++.dg/cpp0x/nullptr17.C b/gcc/testsuite/g++.dg/cpp0x/nullptr17.C
index 96fea44..616cd67 100644
--- a/gcc/testsuite/g++.dg/cpp0x/nullptr17.C
+++ b/gcc/testsuite/g++.dg/cpp0x/nullptr17.C
@@ -1,6 +1,7 @@
 // { dg-do compile { target c++11 } }
 
-// Test that bool is a better overload match than int
+// Used to test that bool is a better overload match than int
+// Updated for DR 1423
 
 template <typename T, typename U> struct tType_equal;
 template <typename T> struct tType_equal<T, T> { typedef void type; };
@@ -16,7 +17,7 @@ bool i( bool );
 void test_i()
 {
   // Overload to bool, not int
-  type_equal<bool>(i(nullptr));
+  type_equal<bool>(i(nullptr));  // { dg-error "direct" }
   decltype(nullptr) mynull = 0;
-  type_equal<bool>(i(mynull));
+  type_equal<bool>(i(mynull));   // { dg-error "direct" }
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/nullptr31.C b/gcc/testsuite/g++.dg/cpp0x/nullptr31.C
new file mode 100644
index 0000000..01b8339
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nullptr31.C
@@ -0,0 +1,11 @@
+// DR 1423, PR c++/52174
+// { dg-do compile { target c++11 } }
+
+bool b1 = nullptr;  // { dg-error "direct" }
+
+bool b2(nullptr);
+bool b3{nullptr};
+
+int  i1 = nullptr;  // { dg-error "cannot convert" }
+int  i2(nullptr);   // { dg-error "cannot convert" }
+int  i3{nullptr};   // { dg-error "cannot convert" }
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C b/gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C
new file mode 100644
index 0000000..7f3c5c4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C
@@ -0,0 +1,18 @@
+// DR 1423, PR c++/52174
+// { dg-do compile { target c++11 } }
+
+template<class T>
+T&& make();
+
+template<class T>
+void sink(T);
+
+template<class T1, class T2,
+  class = decltype(sink<T2>(make<T1>()))
+>
+auto f(int) -> char(&)[1];
+
+template<class, class>
+auto f(...) -> char(&)[2];
+
+static_assert(sizeof(f<decltype(nullptr), bool>(0)) != 1, "");