llvm-gcc treats a tentative definition with a previous

(or follow up) extern declaration with weak_import as 
an actual definition. make clang follows this behavior. 
// rdar://9538608
llvm-gcc treats an extern declaration with weak_import


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133450 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 897b01d093..fe3b3b4f7c 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2039,6 +2039,12 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
   }
   
   mergeDeclAttributes(New, Old, Context);
+  // weak_import on current declaration is applied to previous
+  // tentative definiton.
+  if (New->getAttr<WeakImportAttr>() &&
+      Old->getStorageClass() == SC_None &&
+      !Old->getAttr<WeakImportAttr>())
+    Old->addAttr(::new (Context) WeakImportAttr(SourceLocation(), Context));
 
   // Merge the types.
   MergeVarDeclTypes(New, Old);