From c855ce7ab97aa25c609a5f83e19b27289fede21a Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Thu, 4 Apr 2013 04:40:17 +0000
Subject: Add hasExternalLinkageUncached back with the test that Richard
 provided, but keep the call at the current location.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178741 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/AST/Decl.h                |  4 ++++
 lib/AST/Decl.cpp                        |  4 ++++
 lib/Sema/SemaDecl.cpp                   | 14 +++++++++++++-
 test/Modules/Inputs/linkage-merge-bar.h |  0
 test/Modules/Inputs/linkage-merge-foo.h |  1 +
 test/Modules/Inputs/module.map          | 10 ++++++++++
 test/Modules/linkage-merge.cpp          |  7 +++++++
 7 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 test/Modules/Inputs/linkage-merge-bar.h
 create mode 100644 test/Modules/Inputs/linkage-merge-foo.h
 create mode 100644 test/Modules/linkage-merge.cpp

diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index 0294b9fde8..7927279ddd 100644
--- a/include/clang/AST/Decl.h
+++ b/include/clang/AST/Decl.h
@@ -219,6 +219,10 @@ public:
     return getLinkage() == ExternalLinkage;
   }
 
+  /// \brief True if this decl has external linkage. Don't cache the linkage,
+  /// because we are not finished setting up the redecl chain for the decl.
+  bool hasExternalLinkageUncached() const;
+
   /// \brief Determines the visibility of this entity.
   Visibility getVisibility() const {
     return getLinkageAndVisibility().getVisibility();
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 9505d299ab..bf807aeb1d 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -866,6 +866,10 @@ bool NamedDecl::isLinkageValid() const {
     Linkage(CachedLinkage);
 }
 
+bool NamedDecl::hasExternalLinkageUncached() const {
+  return getLVForDecl(this, LVForExplicitValue).getLinkage() == ExternalLinkage;
+}
+
 Linkage NamedDecl::getLinkage() const {
   if (HasCachedLinkage)
     return Linkage(CachedLinkage);
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 0ad539ef17..436fca35cb 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1614,7 +1614,19 @@ static void filterNonConflictingPreviousDecls(ASTContext &context,
       continue;
 
     // If either has no-external linkage, ignore the old declaration.
-    if (old->getLinkage() != ExternalLinkage || !decl->hasExternalLinkage())
+    // If this declaration would have external linkage if it were the first
+    // declaration of this name, then it may in fact be a redeclaration of
+    // some hidden declaration, so include those too. We don't need to worry
+    // about some previous visible declaration giving this declaration external
+    // linkage, because in that case, we'll mark this declaration as a redecl
+    // of the visible decl, and that decl will already be a redecl of the
+    // hidden declaration if that's appropriate.
+    //
+    // Don't cache this linkage computation, because it's not yet correct: we
+    // may later give this declaration a previous declaration which changes
+    // its linkage.
+    if (old->getLinkage() != ExternalLinkage ||
+        !decl->hasExternalLinkageUncached())
       filter.erase();
   }
 
diff --git a/test/Modules/Inputs/linkage-merge-bar.h b/test/Modules/Inputs/linkage-merge-bar.h
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/test/Modules/Inputs/linkage-merge-foo.h b/test/Modules/Inputs/linkage-merge-foo.h
new file mode 100644
index 0000000000..7ed7775122
--- /dev/null
+++ b/test/Modules/Inputs/linkage-merge-foo.h
@@ -0,0 +1 @@
+int f();
diff --git a/test/Modules/Inputs/module.map b/test/Modules/Inputs/module.map
index 595e5d8846..d20521f9c7 100644
--- a/test/Modules/Inputs/module.map
+++ b/test/Modules/Inputs/module.map
@@ -199,3 +199,13 @@ module builtin {
     header "builtin_sub.h"
   }
 }
+
+module linkage_merge {
+  explicit module foo {
+    header "linkage-merge-foo.h"
+  }
+  explicit module bar {
+    header "linkage-merge-bar.h"
+  }
+
+}
diff --git a/test/Modules/linkage-merge.cpp b/test/Modules/linkage-merge.cpp
new file mode 100644
index 0000000000..dafb0090e7
--- /dev/null
+++ b/test/Modules/linkage-merge.cpp
@@ -0,0 +1,7 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs %s
+
+#include "linkage-merge-bar.h"
+
+static int f(int);
+int f(int);
-- 
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