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.
/////////////////////
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");
