1 files changed, 25 insertions, 2 deletions
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 973911eb840..939941a4c2d 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -8732,8 +8732,10 @@ DeclResult Sema::ActOnExplicitInstantiation(
                                        ? TSK_ExplicitInstantiationDefinition
                                        : TSK_ExplicitInstantiationDeclaration;
 
-  if (TSK == TSK_ExplicitInstantiationDeclaration) {
-    // Check for dllexport class template instantiation declarations.
+  if (TSK == TSK_ExplicitInstantiationDeclaration &&
+      !Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) {
+    // Check for dllexport class template instantiation declarations,
+    // except for MinGW mode.
     for (const ParsedAttr &AL : Attr) {
       if (AL.getKind() == ParsedAttr::AT_DLLExport) {
         Diag(ExternLoc,
@@ -8793,6 +8795,19 @@ DeclResult Sema::ActOnExplicitInstantiation(
   TemplateSpecializationKind PrevDecl_TSK
     = PrevDecl ? PrevDecl->getTemplateSpecializationKind() : TSK_Undeclared;
 
+  if (TSK == TSK_ExplicitInstantiationDefinition && PrevDecl != nullptr &&
+      Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) {
+    // Check for dllexport class template instantiation definitions in MinGW
+    // mode, if a previous declaration of the instantiation was seen.
+    for (const ParsedAttr &AL : Attr) {
+      if (AL.getKind() == ParsedAttr::AT_DLLExport) {
+        Diag(AL.getLoc(),
+             diag::warn_attribute_dllexport_explicit_instantiation_def);
+        break;
+      }
+    }
+  }
+
   if (CheckExplicitInstantiation(*this, ClassTemplate, TemplateNameLoc,
                                  SS.isSet(), TSK))
     return true;
@@ -8949,6 +8964,14 @@ DeclResult Sema::ActOnExplicitInstantiation(
       dllExportImportClassTemplateSpecialization(*this, Def);
     }
 
+    // In MinGW mode, export the template instantiation if the declaration
+    // was marked dllexport.
+    if (PrevDecl_TSK == TSK_ExplicitInstantiationDeclaration &&
+        Context.getTargetInfo().getTriple().isWindowsGNUEnvironment() &&
+        PrevDecl->hasAttr<DLLExportAttr>()) {
+      dllExportImportClassTemplateSpecialization(*this, Def);
+    }
+
     // Set the template specialization kind. Make sure it is set before
     // instantiating the members which will trigger ASTConsumer callbacks.
     Specialization->setTemplateSpecializationKind(TSK);