MS compatibility: always emit dllexported in-class initialized static data members (PR20140)

This makes us emit dllexported in-class initialized static data members (which
are treated as definitions in MSVC), even when they're not referenced.

It also makes their special linkage reflected in the GVA linkage instead of
getting massaged in CodeGen.

Differential Revision: http://reviews.llvm.org/D4563

llvm-svn: 213304

1 files changed, 14 insertions, 1 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 5c271f027fe..bccdae91d2e 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -4781,6 +4781,12 @@ CharUnits ASTContext::getObjCEncodingTypeSize(QualType type) const {
   return sz;
 }
 
+bool ASTContext::isMSStaticDataMemberInlineDefinition(const VarDecl *VD) const {
+  return getLangOpts().MSVCCompat && VD->isStaticDataMember() &&
+         VD->getType()->isIntegralOrEnumerationType() &&
+         !VD->getFirstDecl()->isOutOfLine() && VD->getFirstDecl()->hasInit();
+}
+
 static inline 
 std::string charUnitsToString(const CharUnits &CU) {
   return llvm::itostr(CU.getQuantity());
@@ -7849,6 +7855,12 @@ static GVALinkage basicGVALinkageForVariable(const ASTContext &Context,
                                                : StaticLocalLinkage;
   }
 
+  // MSVC treats in-class initialized static data members as definitions.
+  // By giving them non-strong linkage, out-of-line definitions won't
+  // cause link errors.
+  if (Context.isMSStaticDataMemberInlineDefinition(VD))
+    return GVA_DiscardableODR;
+
   switch (VD->getTemplateSpecializationKind()) {
   case TSK_Undeclared:
   case TSK_ExplicitSpecialization:
@@ -7934,7 +7946,8 @@ bool ASTContext::DeclMustBeEmitted(const Decl *D) {
   const VarDecl *VD = cast<VarDecl>(D);
   assert(VD->isFileVarDecl() && "Expected file scoped var");
 
-  if (VD->isThisDeclarationADefinition() == VarDecl::DeclarationOnly)
+  if (VD->isThisDeclarationADefinition() == VarDecl::DeclarationOnly &&
+      !isMSStaticDataMemberInlineDefinition(VD))
     return false;
 
   // Variables that can be needed in other TUs are required.