diff options
| -rw-r--r-- | clang/lib/AST/ASTContext.cpp | 23 | ||||
| -rw-r--r-- | clang/test/CodeGenCXX/ms-constexpr-var-template.cpp | 11 |
2 files changed, 30 insertions, 4 deletions
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp index dd88c919669..29a80f17eb9 100644 --- a/clang/lib/AST/ASTContext.cpp +++ b/clang/lib/AST/ASTContext.cpp @@ -9905,10 +9905,25 @@ static GVALinkage basicGVALinkageForVariable(const ASTContext &Context, return StrongLinkage; case TSK_ExplicitSpecialization: - return Context.getTargetInfo().getCXXABI().isMicrosoft() && - VD->isStaticDataMember() - ? GVA_StrongODR - : StrongLinkage; + if (Context.getTargetInfo().getCXXABI().isMicrosoft()) { + // If this is a fully specialized constexpr variable template, pretend it + // was marked inline. MSVC 14.21.27702 headers define _Is_integral in a + // header this way, and we don't want to emit non-discardable definitions + // of these variables in every TU that includes <type_traits>. This + // behavior is non-conforming, since another TU could use an extern + // template declaration for this variable, but for constexpr variables, + // it's unlikely for a user to want to do that. This behavior can be + // removed if the headers change to explicitly mark such variable template + // specializations inline. + if (isa<VarTemplateSpecializationDecl>(VD) && VD->isConstexpr()) + return GVA_DiscardableODR; + + // Use ODR linkage for static data members of fully specialized templates + // to prevent duplicate definition errors with MSVC. + if (VD->isStaticDataMember()) + return GVA_StrongODR; + } + return StrongLinkage; case TSK_ExplicitInstantiationDefinition: return GVA_StrongODR; diff --git a/clang/test/CodeGenCXX/ms-constexpr-var-template.cpp b/clang/test/CodeGenCXX/ms-constexpr-var-template.cpp new file mode 100644 index 00000000000..a40f7aacac0 --- /dev/null +++ b/clang/test/CodeGenCXX/ms-constexpr-var-template.cpp @@ -0,0 +1,11 @@ +// RUN: %clang_cc1 -emit-llvm -triple=x86_64-windows-msvc -fms-compatibility %s -o - | FileCheck %s + +template <typename> constexpr bool _Is_integer = false; +template <> constexpr bool _Is_integer<int> = true; +template <> constexpr bool _Is_integer<char> = false; +extern "C" const bool *escape = &_Is_integer<int>; + +// CHECK: @"??$_Is_integer@H@@3_NB" = linkonce_odr dso_local constant i8 1, comdat, align 1 +// Should not emit _Is_integer<char>, since it's not referenced. +// CHECK-NOT: @"??$_Is_integer@D@@3_NB" +// CHECK: @escape = dso_local global i8* @"??$_Is_integer@H@@3_NB", align 8 |
