[cfe-commits] r124236 - in /cfe/trunk: include/clang/Sema/Overload.h lib/Sema/SemaOverload.cpp test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp
Douglas Gregor
dgregor at apple.com
Tue Jan 25 14:19:32 PST 2011
Author: dgregor
Date: Tue Jan 25 16:19:32 2011
New Revision: 124236
URL: http://llvm.org/viewvc/llvm-project?rev=124236&view=rev
Log:
Speculatively implement a tweak to the C++0x overload resolution rules
for reference binding (C++ [over.rank.ics]p3b1sb4), so that we prefer
the binding of an lvalue reference to a function lvalue over the
binding of an rvalue reference. This change resolves the ambiguity
with std::forward and lvalue references to function types in a way
that seems consistent with the original rvalue references proposal.
My proposed wording for this change is shown in
isBetterReferenceBindingKind(); we'll try to get this change adopted
in the C++0x working paper as well.
Modified:
cfe/trunk/include/clang/Sema/Overload.h
cfe/trunk/lib/Sema/SemaOverload.cpp
cfe/trunk/test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp
Modified: cfe/trunk/include/clang/Sema/Overload.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Overload.h?rev=124236&r1=124235&r2=124236&view=diff
==============================================================================
--- cfe/trunk/include/clang/Sema/Overload.h (original)
+++ cfe/trunk/include/clang/Sema/Overload.h Tue Jan 25 16:19:32 2011
@@ -133,24 +133,30 @@
/// Deprecated - Whether this the deprecated conversion of a
/// string literal to a pointer to non-const character data
/// (C++ 4.2p2).
- bool DeprecatedStringLiteralToCharPtr : 1;
+ unsigned DeprecatedStringLiteralToCharPtr : 1;
/// IncompatibleObjC - Whether this is an Objective-C conversion
/// that we should warn about (if we actually use it).
- bool IncompatibleObjC : 1;
+ unsigned IncompatibleObjC : 1;
/// ReferenceBinding - True when this is a reference binding
/// (C++ [over.ics.ref]).
- bool ReferenceBinding : 1;
+ unsigned ReferenceBinding : 1;
/// DirectBinding - True when this is a reference binding that is a
/// direct binding (C++ [dcl.init.ref]).
- bool DirectBinding : 1;
-
- /// RRefBinding - True when this is a reference binding of an rvalue
- /// reference to an rvalue (C++0x [over.ics.rank]p3b4).
- bool RRefBinding : 1;
+ unsigned DirectBinding : 1;
+ /// \brief Whether this is an lvalue reference binding (otherwise, it's
+ /// an rvalue reference binding).
+ unsigned IsLvalueReference : 1;
+
+ /// \brief Whether we're binding to a function lvalue.
+ unsigned BindsToFunctionLvalue : 1;
+
+ /// \brief Whether we're binding to an rvalue.
+ unsigned BindsToRvalue : 1;
+
/// FromType - The type that this conversion is converting
/// from. This is an opaque pointer that can be translated into a
/// QualType.
Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=124236&r1=124235&r2=124236&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
+++ cfe/trunk/lib/Sema/SemaOverload.cpp Tue Jan 25 16:19:32 2011
@@ -170,7 +170,9 @@
DeprecatedStringLiteralToCharPtr = false;
ReferenceBinding = false;
DirectBinding = false;
- RRefBinding = false;
+ IsLvalueReference = true;
+ BindsToFunctionLvalue = false;
+ BindsToRvalue = false;
CopyConstructor = 0;
}
@@ -2324,6 +2326,33 @@
return ImplicitConversionSequence::Indistinguishable;
}
+/// \brief Determine whether one of the given reference bindings is better
+/// than the other based on what kind of bindings they are.
+static bool isBetterReferenceBindingKind(const StandardConversionSequence &SCS1,
+ const StandardConversionSequence &SCS2) {
+ // C++0x [over.ics.rank]p3b4:
+ // -- S1 and S2 are reference bindings (8.5.3) and neither refers to an
+ // implicit object parameter of a non-static member function declared
+ // without a ref-qualifier, and *either* S1 binds an rvalue reference
+ // to an rvalue and S2 binds an lvalue reference *or S1 binds an
+ // lvalue reference to a function lvalue and S2 binds an rvalue
+ // reference*.
+ //
+ // FIXME: Rvalue references. We're going rogue with the above edits,
+ // because the semantics in the current C++0x working paper (N3225 at the
+ // time of this writing) break the standard definition of std::forward
+ // and std::reference_wrapper when dealing with references to functions.
+ // Proposed wording changes submitted to CWG for consideration.
+ //
+ // FIXME: Rvalue references. We don't know if we're dealing with the
+ // implicit object parameter, or if the member function in this case has a
+ // ref qualifier. (Of course, we don't have ref qualifiers yet.)
+ return (!SCS1.IsLvalueReference && SCS1.BindsToRvalue &&
+ SCS2.IsLvalueReference) ||
+ (SCS1.IsLvalueReference && SCS1.BindsToFunctionLvalue &&
+ !SCS2.IsLvalueReference);
+}
+
/// CompareStandardConversionSequences - Compare two standard
/// conversion sequences to determine whether one is better than the
/// other or if they are indistinguishable (C++ 13.3.3.2p3).
@@ -2429,18 +2458,12 @@
return QualCK;
if (SCS1.ReferenceBinding && SCS2.ReferenceBinding) {
- // C++0x [over.ics.rank]p3b4:
- // -- S1 and S2 are reference bindings (8.5.3) and neither refers to an
- // implicit object parameter of a non-static member function declared
- // without a ref-qualifier, and S1 binds an rvalue reference to an
- // rvalue and S2 binds an lvalue reference.
- // FIXME: Rvalue references. We don't know if we're dealing with the
- // implicit object parameter, or if the member function in this case has a
- // ref qualifier. (Of course, we don't have ref qualifiers yet.)
- if (SCS1.RRefBinding != SCS2.RRefBinding)
- return SCS1.RRefBinding ? ImplicitConversionSequence::Better
- : ImplicitConversionSequence::Worse;
-
+ // Check for a better reference binding based on the kind of bindings.
+ if (isBetterReferenceBindingKind(SCS1, SCS2))
+ return ImplicitConversionSequence::Better;
+ else if (isBetterReferenceBindingKind(SCS2, SCS1))
+ return ImplicitConversionSequence::Worse;
+
// C++ [over.ics.rank]p3b4:
// -- S1 and S2 are reference bindings (8.5.3), and the types to
// which the references refer are the same type except for
@@ -2966,7 +2989,9 @@
ICS.Standard.setToType(2, T1);
ICS.Standard.ReferenceBinding = true;
ICS.Standard.DirectBinding = true;
- ICS.Standard.RRefBinding = isRValRef && InitCategory.isRValue();
+ ICS.Standard.IsLvalueReference = !isRValRef;
+ ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
+ ICS.Standard.BindsToRvalue = false;
ICS.Standard.CopyConstructor = 0;
// Nothing more to do: the inaccessibility/ambiguity check for
@@ -3036,7 +3061,9 @@
ICS.Standard.DirectBinding =
S.getLangOptions().CPlusPlus0x ||
(InitCategory.isPRValue() && !T2->isRecordType());
- ICS.Standard.RRefBinding = isRValRef && InitCategory.isRValue();
+ ICS.Standard.IsLvalueReference = !isRValRef;
+ ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
+ ICS.Standard.BindsToRvalue = InitCategory.isRValue();
ICS.Standard.CopyConstructor = 0;
return ICS;
}
@@ -3114,10 +3141,14 @@
// Of course, that's still a reference binding.
if (ICS.isStandard()) {
ICS.Standard.ReferenceBinding = true;
- ICS.Standard.RRefBinding = isRValRef;
+ ICS.Standard.IsLvalueReference = !isRValRef;
+ ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
+ ICS.Standard.BindsToRvalue = true;
} else if (ICS.isUserDefined()) {
ICS.UserDefined.After.ReferenceBinding = true;
- ICS.UserDefined.After.RRefBinding = isRValRef;
+ ICS.Standard.IsLvalueReference = !isRValRef;
+ ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
+ ICS.Standard.BindsToRvalue = true;
}
return ICS;
@@ -3212,7 +3243,11 @@
ICS.Standard.setAllToTypes(ImplicitParamType);
ICS.Standard.ReferenceBinding = true;
ICS.Standard.DirectBinding = true;
- ICS.Standard.RRefBinding = false;
+
+ // FIXME: Rvalue references.
+ ICS.Standard.IsLvalueReference = true;
+ ICS.Standard.BindsToFunctionLvalue = false;
+ ICS.Standard.BindsToRvalue = false;
return ICS;
}
Modified: cfe/trunk/test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp?rev=124236&r1=124235&r2=124236&view=diff
==============================================================================
--- cfe/trunk/test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp (original)
+++ cfe/trunk/test/CXX/over/over.match/over.match.best/over.ics.rank/p3-0x.cpp Tue Jan 25 16:19:32 2011
@@ -50,10 +50,10 @@
};
namespace FunctionReferencesOverloading {
- template<typename T> int &f(typename remove_reference<T>::type&); // expected-note{{candidate function [with T = int (&)(int)]}}
- template<typename T> float &f(typename remove_reference<T>::type&&); // expected-note{{candidate function [with T = int (&)(int)]}}
+ template<typename T> int &f(typename remove_reference<T>::type&);
+ template<typename T> float &f(typename remove_reference<T>::type&&);
void test_f(int (&func_ref)(int)) {
- f<int (&)(int)>(func_ref); // expected-error{{call to 'f' is ambiguous}}
+ int &ir = f<int (&)(int)>(func_ref);
}
}
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