From 0d923af49270ef4beb5d479dac5bda80fc0082ef Mon Sep 17 00:00:00 2001 From: Richard Smith Date: Fri, 26 Apr 2019 01:51:07 +0000 Subject: [PATCH] Add missing diagnostic for explicit instantiation declarations naming internal linkage entities. Such constructs are ill-formed by [temp.explicit]p13. We make a special exception to permit an invalid construct used by libc++ in some build modes: its header declares some functions with the internal_linkage attribute and then (meaninglessly) provides explicit instantiation declarations for them. Luckily, Clang happens to effectively ignore the explicit instantiation declaration when generating code in this case, and this change codifies that behavior. This reinstates part of r359048, reverted in r359076. (The libc++ issue triggering the rollback has been addressed.) llvm-svn: 359259 --- clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 + clang/lib/Sema/SemaTemplate.cpp | 66 +++++++++++++++++------- clang/test/CXX/drs/dr0xx.cpp | 7 ++- clang/test/SemaCXX/PR10177.cpp | 3 +- clang/test/SemaCXX/libcxx_valarray_hack.cpp | 32 ++++++++++++ 5 files changed, 84 insertions(+), 26 deletions(-) create mode 100644 clang/test/SemaCXX/libcxx_valarray_hack.cpp diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 238c9ee..059183d 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -4384,6 +4384,8 @@ def err_explicit_instantiation_of_typedef : Error< "explicit instantiation of typedef %0">; def err_explicit_instantiation_storage_class : Error< "explicit instantiation cannot have a storage class">; +def err_explicit_instantiation_internal_linkage : Error< + "explicit instantiation declaration of %0 with internal linkage">; def err_explicit_instantiation_not_known : Error< "explicit instantiation of %0 does not refer to a function template, " "variable template, member function, member class, or static data member">; diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index 1010370..973911e 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -8619,6 +8619,29 @@ static bool CheckExplicitInstantiationScope(Sema &S, NamedDecl *D, return false; } +/// Common checks for whether an explicit instantiation of \p D is valid. +static bool CheckExplicitInstantiation(Sema &S, NamedDecl *D, + SourceLocation InstLoc, + bool WasQualifiedName, + TemplateSpecializationKind TSK) { + // C++ [temp.explicit]p13: + // An explicit instantiation declaration shall not name a specialization of + // a template with internal linkage. + if (TSK == TSK_ExplicitInstantiationDeclaration && + D->getFormalLinkage() == InternalLinkage) { + S.Diag(InstLoc, diag::err_explicit_instantiation_internal_linkage) << D; + return true; + } + + // C++11 [temp.explicit]p3: [DR 275] + // An explicit instantiation shall appear in an enclosing namespace of its + // template. + if (CheckExplicitInstantiationScope(S, D, InstLoc, WasQualifiedName)) + return true; + + return false; +} + /// Determine whether the given scope specifier has a template-id in it. static bool ScopeSpecifierHasTemplateId(const CXXScopeSpec &SS) { if (!SS.isSet()) @@ -8770,13 +8793,8 @@ DeclResult Sema::ActOnExplicitInstantiation( TemplateSpecializationKind PrevDecl_TSK = PrevDecl ? PrevDecl->getTemplateSpecializationKind() : TSK_Undeclared; - // C++0x [temp.explicit]p2: - // [...] An explicit instantiation shall appear in an enclosing - // namespace of its template. [...] - // - // This is C++ DR 275. - if (CheckExplicitInstantiationScope(*this, ClassTemplate, TemplateNameLoc, - SS.isSet())) + if (CheckExplicitInstantiation(*this, ClassTemplate, TemplateNameLoc, + SS.isSet(), TSK)) return true; ClassTemplateSpecializationDecl *Specialization = nullptr; @@ -8999,12 +9017,7 @@ Sema::ActOnExplicitInstantiation(Scope *S, SourceLocation ExternLoc, = ExternLoc.isInvalid()? TSK_ExplicitInstantiationDefinition : TSK_ExplicitInstantiationDeclaration; - // C++0x [temp.explicit]p2: - // [...] An explicit instantiation shall appear in an enclosing - // namespace of its template. [...] - // - // This is C++ DR 275. - CheckExplicitInstantiationScope(*this, Record, NameLoc, true); + CheckExplicitInstantiation(*this, Record, NameLoc, true, TSK); // Verify that it is okay to explicitly instantiate here. CXXRecordDecl *PrevDecl @@ -9235,8 +9248,7 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S, diag::ext_explicit_instantiation_without_qualified_id) << Prev << D.getCXXScopeSpec().getRange(); - // Check the scope of this explicit instantiation. - CheckExplicitInstantiationScope(*this, Prev, D.getIdentifierLoc(), true); + CheckExplicitInstantiation(*this, Prev, D.getIdentifierLoc(), true, TSK); // Verify that it is okay to explicitly instantiate here. TemplateSpecializationKind PrevTSK = Prev->getTemplateSpecializationKind(); @@ -9411,6 +9423,20 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S, return (Decl*) nullptr; } + // HACK: libc++ has a bug where it attempts to explicitly instantiate the + // functions + // valarray::valarray(size_t) and + // valarray::~valarray() + // that it declared to have internal linkage with the internal_linkage + // attribute. Ignore the explicit instantiation declaration in this case. + if (Specialization->hasAttr() && + TSK == TSK_ExplicitInstantiationDeclaration) { + if (auto *RD = dyn_cast(Specialization->getDeclContext())) + if (RD->getIdentifier() && RD->getIdentifier()->isStr("valarray") && + RD->isInStdNamespace()) + return (Decl*) nullptr; + } + ProcessDeclAttributeList(S, Specialization, D.getDeclSpec().getAttributes()); // In MSVC mode, dllimported explicit instantiation definitions are treated as @@ -9444,11 +9470,11 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S, diag::ext_explicit_instantiation_without_qualified_id) << Specialization << D.getCXXScopeSpec().getRange(); - CheckExplicitInstantiationScope(*this, - FunTmpl? (NamedDecl *)FunTmpl - : Specialization->getInstantiatedFromMemberFunction(), - D.getIdentifierLoc(), - D.getCXXScopeSpec().isSet()); + CheckExplicitInstantiation( + *this, + FunTmpl ? (NamedDecl *)FunTmpl + : Specialization->getInstantiatedFromMemberFunction(), + D.getIdentifierLoc(), D.getCXXScopeSpec().isSet(), TSK); // FIXME: Create some kind of ExplicitInstantiationDecl here. return (Decl*) nullptr; diff --git a/clang/test/CXX/drs/dr0xx.cpp b/clang/test/CXX/drs/dr0xx.cpp index 911aab1..53bd6f3 100644 --- a/clang/test/CXX/drs/dr0xx.cpp +++ b/clang/test/CXX/drs/dr0xx.cpp @@ -869,18 +869,17 @@ namespace dr68 { // dr68: yes } namespace dr69 { // dr69: yes - template static void f() {} + template static void f() {} // #dr69-f // FIXME: Should we warn here? inline void g() { f(); } - // FIXME: This should be rejected, per [temp.explicit]p11. - extern template void f(); + extern template void f(); // expected-error {{explicit instantiation declaration of 'f' with internal linkage}} #if __cplusplus < 201103L // expected-error@-2 {{C++11 extension}} #endif template struct Q {}; Q<&f > q; #if __cplusplus < 201103L - // expected-error@-2 {{internal linkage}} expected-note@-11 {{here}} + // expected-error@-2 {{internal linkage}} expected-note@#dr69-f {{here}} #endif } diff --git a/clang/test/SemaCXX/PR10177.cpp b/clang/test/SemaCXX/PR10177.cpp index 59630be..0d2e792 100644 --- a/clang/test/SemaCXX/PR10177.cpp +++ b/clang/test/SemaCXX/PR10177.cpp @@ -57,11 +57,10 @@ namespace N { } #else -// expected-no-diagnostics namespace { template extern int n; } template int g() { return n; } -namespace { extern template int n; } +namespace { extern template int n; } // expected-error {{explicit instantiation declaration of 'n' with internal linkage}} #endif diff --git a/clang/test/SemaCXX/libcxx_valarray_hack.cpp b/clang/test/SemaCXX/libcxx_valarray_hack.cpp new file mode 100644 index 0000000..03dc573 --- /dev/null +++ b/clang/test/SemaCXX/libcxx_valarray_hack.cpp @@ -0,0 +1,32 @@ +// RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify + +// This is a test for a hack in Clang that works around an issue with libc++'s +// implementation. The header contains explicit +// instantiations of functions that it declared with the internal_linkage +// attribute, which are ill-formed by [temp.explicit]p13 (and meaningless). + +#ifdef BE_THE_HEADER + +#pragma GCC system_header +namespace std { + using size_t = __SIZE_TYPE__; + template struct valarray { + __attribute__((internal_linkage)) valarray(size_t) {} + __attribute__((internal_linkage)) ~valarray() {} + }; + + extern template valarray::valarray(size_t); + extern template valarray::~valarray(); +} + +#else + +#define BE_THE_HEADER +#include "libcxx_valarray_hack.cpp" + +template struct foo { + __attribute__((internal_linkage)) void x() {}; +}; +extern template void foo::x(); // expected-error {{explicit instantiation declaration of 'x' with internal linkage}} + +#endif -- 2.7.4