diff mbox

[C++] PR 52174 aka DR 1423

Message ID 538DFE15.3020800@oracle.com
State New
Headers show

Commit Message

Paolo Carlini June 3, 2014, 4:55 p.m. UTC 
Hi,

On 06/03/2014 05:41 PM, Jason Merrill wrote:
> On 06/03/2014 11:24 AM, Paolo Carlini wrote:
>> +      if (NULLPTR_TYPE_P (from) && (flags & LOOKUP_ONLYCONVERTING))
>> +        conv->bad_p = true;
>
> Thanks.  What kind of error message do we get with this change? Would 
> adding something to convert_like_real provide a more helpful diagnostic?
We get the default:

invalid conversion from ‘std::nullptr_t’ to ‘bool’ [-fpermissive]

Maybe something like the below then?!?

Thanks,
Paolo.

/////////////////////

Comments

Jason Merrill June 3, 2014, 5:22 p.m. UTC | #1 
OK, thanks.

Jason
diff mbox

Patch

Index: gcc/cp/call.c
===================================================================
--- gcc/cp/call.c	(revision 211162)
+++ gcc/cp/call.c	(working copy)
@@ -1311,10 +1311,10 @@  standard_conversion (tree to, tree from, tree expr
     {
       /* [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
 		  && 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, t
 	    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)
Index: gcc/testsuite/g++.dg/cpp0x/nullptr17.C
===================================================================
--- gcc/testsuite/g++.dg/cpp0x/nullptr17.C	(revision 211162)
+++ gcc/testsuite/g++.dg/cpp0x/nullptr17.C	(working copy)
@@ -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" }
 }
Index: gcc/testsuite/g++.dg/cpp0x/nullptr31.C
===================================================================
--- gcc/testsuite/g++.dg/cpp0x/nullptr31.C	(revision 0)
+++ gcc/testsuite/g++.dg/cpp0x/nullptr31.C	(working copy)
@@ -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" }
Index: gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C
===================================================================
--- gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C	(revision 0)
+++ gcc/testsuite/g++.dg/cpp0x/sfinae-nullptr1.C	(working copy)
@@ -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, "");
Index: libstdc++-v3/testsuite/20_util/is_assignable/value.cc
===================================================================
--- libstdc++-v3/testsuite/20_util/is_assignable/value.cc	(revision 211151)
+++ libstdc++-v3/testsuite/20_util/is_assignable/value.cc	(working copy)
@@ -174,7 +174,7 @@  static_assert(!std::is_assignable<bool&, SE>::valu
 static_assert(std::is_assignable<bool&, void*>::value, "Error");
 static_assert(std::is_assignable<bool&, int B::*>::value, "Error");
 static_assert(std::is_assignable<bool&, void*>::value, "Error");
-static_assert(std::is_assignable<bool&, std::nullptr_t>::value, "Error");
+static_assert(!std::is_assignable<bool&, std::nullptr_t>::value, "Error");
 
 static_assert(std::is_assignable<std::nullptr_t&,
 std::nullptr_t>::value, "Error");