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When performing copy initialization (= "implicit conversion", here) to 

a class type from itself or a derived class thereof, enumerate
constructors and permit user-defined conversions to the arguments of
those constructors. This fixes the wacky implicit conversion sequence
used in std::auto_ptr's lame emulation of move semantics.

llvm-svn: 88670
This commit is contained in:
Douglas Gregor 2009-11-13 18:44:21 +00:00
parent 07eae02fc7
commit 379d84b7ed
2 changed files with 39 additions and 6 deletions
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15
clang/lib/Sema/SemaOverload.cpp
View File

@ -1399,6 +1399,13 @@ Sema::OverloadingResult Sema::IsUserDefinedConversion(
// functions are all the converting constructors (12.3.1) of
// that class. The argument list is the expression-list within
// the parentheses of the initializer.
bool SuppressUserConversions = !UserCast;
if (Context.hasSameUnqualifiedType(ToType, From->getType()) ||
IsDerivedFrom(From->getType(), ToType)) {
SuppressUserConversions = false;
AllowConversionFunctions = false;
}
DeclarationName ConstructorName
= Context.DeclarationNames.getCXXConstructorName(
Context.getCanonicalType(ToType).getUnqualifiedType());
@ -1420,15 +1427,13 @@ Sema::OverloadingResult Sema::IsUserDefinedConversion(
Constructor->isConvertingConstructor(AllowExplicit)) {
if (ConstructorTmpl)
AddTemplateOverloadCandidate(ConstructorTmpl, false, 0, 0, &From,
1, CandidateSet,
/*SuppressUserConversions=*/!UserCast,
ForceRValue);
1, CandidateSet,
SuppressUserConversions, ForceRValue);
else
// Allow one user-defined conversion when user specifies a
// From->ToType conversion via an static cast (c-style, etc).
AddOverloadCandidate(Constructor, &From, 1, CandidateSet,
/*SuppressUserConversions=*/!UserCast,
ForceRValue);
SuppressUserConversions, ForceRValue);
}
}
}

30
clang/test/SemaCXX/conversion-function.cpp
View File

@ -1,4 +1,4 @@
// RUN: clang-cc -fsyntax-only -verify %s
// RUN: clang-cc -fsyntax-only -verify %s
class X {
public:
operator bool();
@ -93,3 +93,31 @@ void f(Yb& a) {
char ch = a; // OK. calls Yb::operator char();
}
// Test conversion + copy construction.
class AutoPtrRef { };
class AutoPtr {
// FIXME: Using 'unavailable' since we do not have access control yet.
// FIXME: The error message isn't so good.
AutoPtr(AutoPtr &) __attribute__((unavailable));
public:
AutoPtr();
AutoPtr(AutoPtrRef);
operator AutoPtrRef();
};
AutoPtr make_auto_ptr();
AutoPtr test_auto_ptr(bool Cond) {
AutoPtr p1( make_auto_ptr() );
AutoPtr p;
if (Cond)
return p; // expected-error{{incompatible type returning}}
return AutoPtr();
}