Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -7508,6 +7508,10 @@
                                   SourceLocation WeakNameLoc,
                                   SourceLocation AliasNameLoc);
 
+  /// HandleDeferredPragmaRedefineExtname - Deferred handling of
+  // '\#pragma redefine_extname' for given declration.
+  template <typename T> void HandleDeferredPragmaRedefineExtname(T *Decl);
+
   /// ActOnPragmaWeakAlias - Called on well formed \#pragma weak ident = ident.
   void ActOnPragmaWeakAlias(IdentifierInfo* WeakName,
                             IdentifierInfo* AliasName,
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -5946,14 +5946,9 @@
 
     NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),
                                                 Context, Label, 0));
-  } else if (!ExtnameUndeclaredIdentifiers.empty()) {
-    llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
-      ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
-    if (I != ExtnameUndeclaredIdentifiers.end()) {
-      NewVD->addAttr(I->second);
-      ExtnameUndeclaredIdentifiers.erase(I);
-    }
-  }
+  // Deferred handling of "redefine_extname" pragma.
+  } else
+    HandleDeferredPragmaRedefineExtname(NewVD);
 
   // Diagnose shadowed variables before filtering for scope.
   if (D.getCXXScopeSpec().isEmpty())
@@ -7468,14 +7463,9 @@
     StringLiteral *SE = cast<StringLiteral>(E);
     NewFD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0), Context,
                                                 SE->getString(), 0));
-  } else if (!ExtnameUndeclaredIdentifiers.empty()) {
-    llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
-      ExtnameUndeclaredIdentifiers.find(NewFD->getIdentifier());
-    if (I != ExtnameUndeclaredIdentifiers.end()) {
-      NewFD->addAttr(I->second);
-      ExtnameUndeclaredIdentifiers.erase(I);
-    }
-  }
+  // Deferred handling of "redefine_extname" pragma.
+  } else
+    HandleDeferredPragmaRedefineExtname(NewFD);
 
   // Copy the parameter declarations from the declarator D to the function
   // declaration NewFD, if they are available.  First scavenge them into Params.
@@ -14266,6 +14256,24 @@
     (void)ExtnameUndeclaredIdentifiers.insert(std::make_pair(Name, Attr));
 }
 
+template<typename T>
+void Sema::HandleDeferredPragmaRedefineExtname(T *Decl) {
+  if (ExtnameUndeclaredIdentifiers.empty())
+    return;
+
+  // Declaration is not suitable for pragma redefine_extname
+  if (!(Decl->getDeclContext()->isTranslationUnit() || Decl->isExternC()) ||
+      !Decl->hasExternalFormalLinkage())
+    return;
+
+  llvm::DenseMap<IdentifierInfo *, AsmLabelAttr *>::iterator I =
+      ExtnameUndeclaredIdentifiers.find(Decl->getIdentifier());
+  if (I != ExtnameUndeclaredIdentifiers.end()) {
+    Decl->addAttr(I->second);
+    ExtnameUndeclaredIdentifiers.erase(I);
+  }
+}
+
 void Sema::ActOnPragmaWeakID(IdentifierInfo* Name,
                              SourceLocation PragmaLoc,
                              SourceLocation NameLoc) {
Index: test/CodeGen/redefine_extname.c
===================================================================
--- test/CodeGen/redefine_extname.c
+++ test/CodeGen/redefine_extname.c
@@ -13,3 +13,14 @@
 // CHECK:   call i32 @real()
 // Check that this also works with variables names
 // CHECK:   load i32, i32* @alias
+
+// This is a case when redefenition is deferred *and* we have a local of the
+// same name. PR23923.
+#pragma redefine_extname foo bar
+int f() {
+  int foo = 0;
+  return foo;
+}
+extern int foo() { return 1; }
+// CHECK: define i32 @bar()
+