Index: include/clang/AST/Decl.h =================================================================== --- include/clang/AST/Decl.h +++ include/clang/AST/Decl.h @@ -1778,11 +1778,26 @@ SourceRange getSourceRange() const override LLVM_READONLY; - /// \brief Returns true if the function has a body (definition). The - /// function body might be in any of the (re-)declarations of this - /// function. The variant that accepts a FunctionDecl pointer will - /// set that function declaration to the actual declaration - /// containing the body (if there is one). + // Function definitions. + // + // A function declaration may be: + // - a non defining declaration, + // - a definition. A function may be defined because: + // - it has a body, or will have it in the case of late parsing. + // - it has an uninstantiated body. The body does not exist because the + // function is not used yet, but the declaration is considered a + // definition and does not allow other definition of this function. + // - it does not have a user specified body, but it does not allow + // redefinition, because it is deleted/defaulted or is defined through + // some other mechanism (alias, ifunc). + + /// Returns true if the function has a body. + /// + /// The function body might be in any of the (re-)declarations of this + /// function. The variant that accepts a FunctionDecl pointer will set that + /// function declaration to the actual declaration containing the body (if + /// there is one). + /// bool hasBody(const FunctionDecl *&Definition) const; bool hasBody() const override { @@ -1794,9 +1809,12 @@ /// not require any specific codegen. bool hasTrivialBody() const; - /// isDefined - Returns true if the function is defined at all, including - /// a deleted definition. Except for the behavior when the function is - /// deleted, behaves like hasBody. + /// Returns true if the function has a definition that does not need to be + /// instantiated. + /// + /// The variant that accepts a FunctionDecl pointer will set that function + /// declaration to the declaration that is a definition (if there is one). + /// bool isDefined(const FunctionDecl *&Definition) const; virtual bool isDefined() const { @@ -1840,9 +1858,8 @@ hasDefiningAttr(); } - /// doesThisDeclarationHaveABody - Returns whether this specific - /// declaration of the function has a body - that is, if it is a non- - /// deleted definition. + /// Returns whether this specific declaration of the function has a body. + /// bool doesThisDeclarationHaveABody() const { return Body || IsLateTemplateParsed; } Index: lib/Sema/SemaDecl.cpp =================================================================== --- lib/Sema/SemaDecl.cpp +++ lib/Sema/SemaDecl.cpp @@ -11886,9 +11886,31 @@ const FunctionDecl *EffectiveDefinition, SkipBodyInfo *SkipBody) { const FunctionDecl *Definition = EffectiveDefinition; + if (!Definition && + !FD->isDefined(Definition) + && FD->getDeclContext()->isFileContext()) { + // If this is a friend function defined in a class template, it does not + // have a body until it is used, nevertheless it is a definition. The + // following code must produce redefinition error: + // + // template struct C20 { friend void func_20() {} }; + // C20 c20i; + // void func_20() {} + // + for (auto I : FD->redecls()) { + if (I != FD && !I->isInvalidDecl() && + I->getFriendObjectKind() != Decl::FOK_None) { + if (FunctionDecl *Original = I->getInstantiatedFromMemberFunction()) { + if (Original->isThisDeclarationADefinition()) { + Definition = I; + break; + } + } + } + } + } if (!Definition) - if (!FD->isDefined(Definition)) - return; + return; if (canRedefineFunction(Definition, getLangOpts())) return; Index: lib/Sema/SemaTemplateInstantiateDecl.cpp =================================================================== --- lib/Sema/SemaTemplateInstantiateDecl.cpp +++ lib/Sema/SemaTemplateInstantiateDecl.cpp @@ -1804,45 +1804,24 @@ // apply to non-template function declarations and definitions also apply // to these implicit definitions. if (D->isThisDeclarationADefinition()) { - // Check for a function body. - const FunctionDecl *Definition = nullptr; - if (Function->isDefined(Definition) && - Definition->getTemplateSpecializationKind() == TSK_Undeclared) { - SemaRef.Diag(Function->getLocation(), diag::err_redefinition) - << Function->getDeclName(); - SemaRef.Diag(Definition->getLocation(), diag::note_previous_definition); - } - // Check for redefinitions due to other instantiations of this or - // a similar friend function. - else for (auto R : Function->redecls()) { - if (R == Function) - continue; - - // If some prior declaration of this function has been used, we need - // to instantiate its definition. - if (!QueuedInstantiation && R->isUsed(false)) { - if (MemberSpecializationInfo *MSInfo = - Function->getMemberSpecializationInfo()) { - if (MSInfo->getPointOfInstantiation().isInvalid()) { - SourceLocation Loc = R->getLocation(); // FIXME - MSInfo->setPointOfInstantiation(Loc); - SemaRef.PendingLocalImplicitInstantiations.push_back( - std::make_pair(Function, Loc)); - QueuedInstantiation = true; - } - } - } - - // If some prior declaration of this function was a friend with an - // uninstantiated definition, reject it. - if (R->getFriendObjectKind()) { - if (const FunctionDecl *RPattern = - R->getTemplateInstantiationPattern()) { - if (RPattern->isDefined(RPattern)) { - SemaRef.Diag(Function->getLocation(), diag::err_redefinition) - << Function->getDeclName(); - SemaRef.Diag(R->getLocation(), diag::note_previous_definition); - break; + SemaRef.CheckForFunctionRedefinition(Function); + if (!Function->isInvalidDecl()) { + for (auto R : Function->redecls()) { + if (R == Function) + continue; + + // If some prior declaration of this function has been used, we need + // to instantiate its definition. + if (!QueuedInstantiation && R->isUsed(false)) { + if (MemberSpecializationInfo *MSInfo = + Function->getMemberSpecializationInfo()) { + if (MSInfo->getPointOfInstantiation().isInvalid()) { + SourceLocation Loc = R->getLocation(); // FIXME + MSInfo->setPointOfInstantiation(Loc); + SemaRef.PendingLocalImplicitInstantiations.push_back( + std::make_pair(Function, Loc)); + QueuedInstantiation = true; + } } } } Index: test/SemaCXX/friend2.cpp =================================================================== --- test/SemaCXX/friend2.cpp +++ test/SemaCXX/friend2.cpp @@ -101,6 +101,34 @@ friend void func_12(int x = 0); // expected-error{{friend declaration specifying a default argument must be the only declaration}} }; +// Friend function with uninstantiated body is still a definition. + +template struct C20 { + friend void func_20() {} // expected-note{{previous definition is here}} +}; +C20 c20i; +void func_20() {} // expected-error{{redefinition of 'func_20'}} + +template struct C21a { + friend void func_21() {} // expected-note{{previous definition is here}} +}; +template struct C21b { + friend void func_21() {} // expected-error{{redefinition of 'func_21'}} +}; +C21a c21ai; +C21b c21bi; // expected-note{{in instantiation of template class 'C21b' requested here}} + +template struct C22a { + friend void func_22() {} // expected-note{{previous definition is here}} +}; +template struct C22b { + friend void func_22(); +}; +C22a c22ai; +C22b c22bi; +void func_22() {} // expected-error{{redefinition of 'func_22'}} + + namespace pr22307 {