[clang] Properly apply attributes on explicit instantiations of static data members

[ldionne]

Summary

https://llvm.org/PR39118

[erik.pilkington]

Add some reviewers.

[aaron.ballman]

This seems reasonable to me, but I'd feel most comfortable if @rsmith also signed off on it.

[rnk]

This code dates back to rL187762, which added this check. I think it should always pass for a variable template, but it fails for an explicit instantiation of a static data member of a class template. I think it's correct to remove it.

cfe/trunk/lib/Sema/SemaTemplate.cpp

if (!R->isFunctionType()) {
     bool HasNoEffect = false;
     if (CheckSpecializationInstantiationRedecl(D.getIdentifierLoc(), TSK, Prev,
                                                PrevTSK, POI, HasNoEffect))
       return true;
 
     if (!HasNoEffect) {
       // Instantiate static data member or variable template.
       Prev->setTemplateSpecializationKind(TSK, D.getIdentifierLoc());
-      if (PrevTemplate) {
-        // Merge attributes.
-        ProcessDeclAttributeList(S, Prev, D.getDeclSpec().getAttributes());
-      }
       if (TSK == TSK_ExplicitInstantiationDefinition)
         InstantiateVariableDefinition(D.getIdentifierLoc(), Prev);
     }
 
     // Check the new variable specialization against the parsed input.
     if (PrevTemplate && Prev && !Context.hasSameType(Prev->getType(), R)) {
       Diag(T->getTypeLoc().getBeginLoc(),
            diag::err_invalid_var_template_spec_type)

cfe/trunk/test/SemaCXX/attr-on-explicit-template-instantiation.cpp

+// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
+
+// PR39118
+// Make sure that attributes are properly applied to explicit template
+// instantiations.
+
+#define HIDDEN __attribute__((__visibility__("hidden")))
+#define VISIBLE __attribute__((__visibility__("default")))
+
+namespace ns HIDDEN {
+    struct A { };
+    template <typename T> struct B { static A a; };
+    template <typename T> A B<T>::a;
+
+    // CHECK: @_ZN2ns1BIiE1aE = weak_odr global
+    // CHECK-NOT: hidden
+    template VISIBLE A B<int>::a;
+}
+
+struct C { };
+template <typename T> struct D { static C c; };
+template <typename T> C D<T>::c;
+
+// CHECK-DAG: @_ZN1DIiE1cB3TAGE
+template __attribute__((abi_tag("TAG"))) C D<int>::c;