From 747836e5c79b5e12fe9cfb9b724dc4edeb115419 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Thu, 14 Feb 2013 03:31:26 +0000
Subject: [PATCH] Partially revert r175117 so that we don't break assumptions
 about how static functions in extern "C" contexts are mangled. Should fix the
 bootstrap.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175132 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/ItaniumMangle.cpp     | 9 +++++++++
 lib/Sema/SemaOverload.cpp     | 8 ++++++++
 test/CodeGenCXX/c-linkage.cpp | 8 +++-----
 test/SemaCXX/linkage2.cpp     | 8 ++++----
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index e9a3b03483..1f95a2fee0 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -381,6 +381,15 @@ bool ItaniumMangleContext::shouldMangleDeclName(const NamedDecl *D) {
     // mangling.
     if (!FD->getDeclName().isIdentifier() || L == CXXLanguageLinkage)
       return true;
+
+    // FIXME: Users assume they know the mangling of static functions
+    // declared in extern "C" contexts, so we cannot always mangle them.
+    // As an improvement, maybe we could mangle them only if they are actually
+    // overloaded.
+    const DeclContext *DC = FD->getDeclContext();
+    if (!DC->isRecord() &&
+        FD->getFirstDeclaration()->getDeclContext()->isExternCContext())
+      return false;
   }
 
   // Otherwise, no mangling is done outside C++ mode.
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 9bba5f6c78..20fb7a768b 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -974,6 +974,14 @@ static bool canBeOverloaded(const FunctionDecl &D) {
   if (D.isMain())
     return false;
 
+  // FIXME: Users assume they know the mangling of static functions
+  // declared in extern "C" contexts. For now just disallow overloading these
+  // functions so that we can avoid mangling them.
+  const DeclContext *DC = D.getDeclContext();
+  if (!DC->isRecord() &&
+      D.getFirstDeclaration()->getDeclContext()->isExternCContext())
+    return false;
+
   return true;
 }
 
diff --git a/test/CodeGenCXX/c-linkage.cpp b/test/CodeGenCXX/c-linkage.cpp
index a0a496d09e..c31ad43860 100644
--- a/test/CodeGenCXX/c-linkage.cpp
+++ b/test/CodeGenCXX/c-linkage.cpp
@@ -15,12 +15,10 @@ extern "C" {
 extern "C" {
   static void test2_f() {
   }
-  // CHECK: define internal void @_Z7test2_fv
-  static void test2_f(int x) {
-  }
-  // CHECK: define internal void @_Z7test2_fi
+  // This is not required by the standard, but users assume they know
+  // the mangling of static functions in extern "C" contexts.
+  // CHECK: define internal void @test2_f(
   void test2_use() {
     test2_f();
-    test2_f(42);
   }
 }
diff --git a/test/SemaCXX/linkage2.cpp b/test/SemaCXX/linkage2.cpp
index 2cee581b49..744741b7ca 100644
--- a/test/SemaCXX/linkage2.cpp
+++ b/test/SemaCXX/linkage2.cpp
@@ -12,12 +12,12 @@ namespace test1 {
   }
 }
 
-// This is OK. Both test2_f don't have language linkage since they have
-// internal linkage.
+// FIXME: This should be OK. Both test2_f don't have language linkage since they
+// have internal linkage.
 extern "C" {
-  static void test2_f() {
+  static void test2_f() { // expected-note {{previous definition is here}}
   }
-  static void test2_f(int x) {
+  static void test2_f(int x) { // expected-error {{conflicting types for 'test2_f'}}
   }
 }
 
-- 
2.40.0