From 5db60c2ca8308919348af0c96f98d87a888d8d7c Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Tue, 14 May 2019 10:11:33 +0000
Subject: [PATCH] Revert r360637 "PR41817: Fix regression in r359260 that
 caused the MS compatibility"

> extension allowing a "static" declaration to follow an "extern"
> declaration to stop working.

It introduced asserts for some "static-following-extern" cases, breaking the
Chromium build. See the cfe-commits thread for reproducer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360657 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/Decl.cpp                       | 41 ++++----------------------
 test/CodeGen/ms-compat-extern-static.c | 11 -------
 2 files changed, 6 insertions(+), 46 deletions(-)
 delete mode 100644 test/CodeGen/ms-compat-extern-static.c

diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 1ca66cfb5f..4e42dd7d3b 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -613,41 +613,12 @@ static LinkageInfo getExternalLinkageFor(const NamedDecl *D) {
 static StorageClass getStorageClass(const Decl *D) {
   if (auto *TD = dyn_cast<TemplateDecl>(D))
     D = TD->getTemplatedDecl();
-  if (!D)
-    return SC_None;
-
-  if (auto *VD = dyn_cast<VarDecl>(D)) {
-    // Generally, the storage class is determined by the first declaration.
-    auto SC = VD->getCanonicalDecl()->getStorageClass();
-
-    // ... except that MSVC permits an 'extern' declaration to be redeclared
-    // 'static' as an extension.
-    if (SC == SC_Extern) {
-      for (auto *Redecl : VD->redecls()) {
-        if (Redecl->getStorageClass() == SC_Static)
-          return SC_Static;
-        if (Redecl->getStorageClass() != SC_Extern &&
-            !Redecl->isLocalExternDecl() && !Redecl->getFriendObjectKind())
-          break;
-      }
-    }
-    return SC;
+  if (D) {
+    if (auto *VD = dyn_cast<VarDecl>(D))
+      return VD->getStorageClass();
+    if (auto *FD = dyn_cast<FunctionDecl>(D))
+      return FD->getStorageClass();
   }
-
-  if (auto *FD = dyn_cast<FunctionDecl>(D)) {
-    auto SC = FD->getCanonicalDecl()->getStorageClass();
-    if (SC == SC_Extern) {
-      for (auto *Redecl : FD->redecls()) {
-        if (Redecl->getStorageClass() == SC_Static)
-          return SC_Static;
-        if (Redecl->getStorageClass() != SC_Extern &&
-            !Redecl->isLocalExternDecl() && !Redecl->getFriendObjectKind())
-          break;
-      }
-    }
-    return SC;
-  }
-
   return SC_None;
 }
 
@@ -663,7 +634,7 @@ LinkageComputer::getLVForNamespaceScopeDecl(const NamedDecl *D,
   //   A name having namespace scope (3.3.6) has internal linkage if it
   //   is the name of
 
-  if (getStorageClass(D) == SC_Static) {
+  if (getStorageClass(D->getCanonicalDecl()) == SC_Static) {
     // - a variable, variable template, function, or function template
     //   that is explicitly declared static; or
     // (This bullet corresponds to C99 6.2.2p3.)
diff --git a/test/CodeGen/ms-compat-extern-static.c b/test/CodeGen/ms-compat-extern-static.c
deleted file mode 100644
index 2ad60ef7bc..0000000000
--- a/test/CodeGen/ms-compat-extern-static.c
+++ /dev/null
@@ -1,11 +0,0 @@
-// RUN: %clang_cc1 -emit-llvm %s -o - -fms-extensions -triple x86_64-windows | FileCheck %s
-
-// CHECK: @n = internal global i32 1
-extern int n;
-static int n = 1;
-int *use = &n;
-
-// CHECK: define internal void @f(
-extern void f();
-static void f() {}
-void g() { return f(); }
-- 
2.40.0