C++1y sized deallocation: if we have a use, but not a definition, of a sized

deallocation function (and the corresponding unsized deallocation function has
been declared), emit a weak discardable definition of the function that
forwards to the corresponding unsized deallocation.

This allows a C++ standard library implementation to provide both a sized and
an unsized deallocation function, where the unsized one does not just call the
sized one, for instance by putting both in the same object file within an
archive.

llvm-svn: 194055

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1406,6 +1406,12 @@ CodeGenModule::GetOrCreateLLVMFunction(StringRef MangledName,
     DeferredDeclsToEmit.push_back(DDI->second);
     DeferredDecls.erase(DDI);
 
+  // Otherwise, if this is a sized deallocation function, emit a weak definition
+  // for it at the end of the translation unit.
+  } else if (D && cast<FunctionDecl>(D)
+                      ->getCorrespondingUnsizedGlobalDeallocationFunction()) {
+    DeferredDeclsToEmit.push_back(GD);
+
   // Otherwise, there are cases we have to worry about where we're
   // using a declaration for which we must emit a definition but where
   // we might not find a top-level definition: