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-rw-r--r--lib/AST/ASTContext.cpp23
1 files changed, 19 insertions, 4 deletions
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 468c7f47657d..93bdaafc2ac6 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -9814,10 +9814,25 @@ 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;