[clang] Set dllimport on Objective C ivar offsets (PR #107604)

[Saleem Abdulrasool via cfe-commits]

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@@ -1699,11 +1699,18 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
   llvm::Value *EmitIvarOffset(CodeGenFunction &CGF,
                               const ObjCInterfaceDecl *Interface,
                               const ObjCIvarDecl *Ivar) override {
-    const std::string Name = GetIVarOffsetVariableName(Ivar->getContainingInterface(), Ivar);
+    const ObjCInterfaceDecl *ContainingInterface =
+        Ivar->getContainingInterface();
+    const std::string Name =
+        GetIVarOffsetVariableName(ContainingInterface, Ivar);
     llvm::GlobalVariable *IvarOffsetPointer = TheModule.getNamedGlobal(Name);
-    if (!IvarOffsetPointer)
+    if (!IvarOffsetPointer) {
       IvarOffsetPointer = new llvm::GlobalVariable(TheModule, IntTy, false,
               llvm::GlobalValue::ExternalLinkage, nullptr, Name);
+      if (Ivar->getAccessControl() != ObjCIvarDecl::Private &&
+          Ivar->getAccessControl() != ObjCIvarDecl::Package)
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compnerd wrote:

What is no explicit access control specified treated as? I wonder if this should be explicitly checking for `public` or `protected` access controls instead.

https://github.com/llvm/llvm-project/pull/107604