From b567f63bf385a77f20f3118e9eb28734ba9f7cdd Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Thu, 31 Jul 2014 19:29:39 +0000
Subject: [PATCH] Local extern redeclarations of dllimport variables stay
 dllimport even if they don't specify the attribute

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214425 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaDecl.cpp    | 5 +++--
 test/CodeGen/dllimport.c | 8 ++++++++
 test/Sema/dllimport.c    | 4 ++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 4abbbebf80..d24cf6a7be 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5047,7 +5047,7 @@ static void checkDLLAttributeRedeclaration(Sema &S, NamedDecl *OldDecl,
   }
 
   // A redeclaration is not allowed to drop a dllimport attribute, the only
-  // exception being inline function definitions.
+  // exceptions being inline function definitions and local extern declarations.
   // NB: MSVC converts such a declaration to dllexport.
   bool IsInline = false, IsStaticDataMember = false;
   if (const auto *VD = dyn_cast<VarDecl>(NewDecl))
@@ -5057,7 +5057,8 @@ static void checkDLLAttributeRedeclaration(Sema &S, NamedDecl *OldDecl,
   else if (const auto *FD = dyn_cast<FunctionDecl>(NewDecl))
     IsInline = FD->isInlined();
 
-  if (OldImportAttr && !HasNewAttr && !IsInline && !IsStaticDataMember) {
+  if (OldImportAttr && !HasNewAttr && !IsInline && !IsStaticDataMember &&
+      !NewDecl->isLocalExternDecl()) {
     S.Diag(NewDecl->getLocation(),
            diag::warn_redeclaration_without_attribute_prev_attribute_ignored)
       << NewDecl << OldImportAttr;
diff --git a/test/CodeGen/dllimport.c b/test/CodeGen/dllimport.c
index 32ee81f859..6ed60ea1e2 100644
--- a/test/CodeGen/dllimport.c
+++ b/test/CodeGen/dllimport.c
@@ -44,6 +44,14 @@ __declspec(dllimport) extern int GlobalRedecl3;
                       extern int GlobalRedecl3; // dllimport ignored
 USEVAR(GlobalRedecl3)
 
+// Redeclaration in local context.
+// CHECK: @GlobalRedecl4 = external dllimport global i32
+__declspec(dllimport) int GlobalRedecl4;
+int functionScope() {
+  extern int GlobalRedecl4; // still dllimport
+  return GlobalRedecl4;
+}
+
 
 
 //===----------------------------------------------------------------------===//
diff --git a/test/Sema/dllimport.c b/test/Sema/dllimport.c
index 2702453b61..30ea4f3089 100644
--- a/test/Sema/dllimport.c
+++ b/test/Sema/dllimport.c
@@ -74,6 +74,7 @@ __declspec(dllimport) static int StaticGlobal; // expected-error{{'StaticGlobal'
 __declspec(dllimport) float LocalRedecl1; // expected-note{{previous definition is here}}
 __declspec(dllimport) float LocalRedecl2; // expected-note{{previous definition is here}}
 __declspec(dllimport) float LocalRedecl3; // expected-note{{previous definition is here}}
+__declspec(dllimport) float LocalRedecl4;
 void functionScope() {
   __declspec(dllimport) int LocalRedecl1; // expected-error{{redefinition of 'LocalRedecl1' with a different type: 'int' vs 'float'}}
   int *__attribute__((dllimport)) LocalRedecl2; // expected-error{{redefinition of 'LocalRedecl2' with a different type: 'int *' vs 'float'}}
@@ -84,6 +85,9 @@ void functionScope() {
   __declspec(dllimport) extern int ExternLocalVarDecl;
   __declspec(dllimport) extern int ExternLocalVarDef = 1; // expected-error{{definition of dllimport data}}
   __declspec(dllimport) static int StaticLocalVar; // expected-error{{'StaticLocalVar' must have external linkage when declared 'dllimport'}}
+
+  // Local extern redeclaration does not drop the attribute.
+  extern float LocalRedecl4;
 }
 
 
-- 
2.40.0