[PATCH] Start adding support for dllimport/dllexport on classes (PR11170)

[Hans Wennborg]

Thanks everyone for the review!

================
Comment at: lib/CodeGen/CGVTables.cpp:663
@@ +662,3 @@
+  } else if (RD->hasAttr<DLLImportAttr>()) {
+    // Imported functions are available externally.
+    DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
----------------
Reid Kleckner wrote:
> "Imported vtables"
Done.

================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:920
@@ +919,3 @@
+
+    if (RD->hasAttr<DLLImportAttr>())
+      VTable->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
----------------
Reid Kleckner wrote:
> This should probably also go in getAddrOfVTable.  I wonder if that explains the MinGW issue.
Done.

I guess for MinGW we'd need to add it to the Itanium ABI's getAddrOfVTable.

================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:1230
@@ -1220,1 +1229,3 @@
 
+  if (RD->hasAttr<DLLImportAttr>())
+    GV->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
----------------
Reid Kleckner wrote:
> This should be in getAddrOfVBTable.  We might want to avoid emitting available externally vbtables at -O0 and simply import them from the dll.
Done.

================
Comment at: lib/Sema/SemaDeclCXX.cpp:4385
@@ +4384,3 @@
+    NewAttr->setInherited(true);
+    Member->addAttr(NewAttr);
+
----------------
Nico Rieck wrote:
> Reid Kleckner wrote:
> > We shouldn't be adding these attributes to FieldDecls.  I suppose we want to export nested classes, though.
> I'd use a whitelist and only propagate it to methods and static data members. Nested classes aren't automatically exported or imported.
Oops, this fell out when I merged the separate function into this loop. Fixed now.

http://reviews.llvm.org/D3877