Make __declspec(selectany) turn variable declartions into definitions.

Fixes PR23242.

llvm-svn: 235046

3 files changed, 19 insertions, 2 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 2ae73de5074..349b7b43d1a 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1926,14 +1926,14 @@ VarDecl::DefinitionKind VarDecl::isThisDeclarationADefinition(
       getTemplateSpecializationKind() != TSK_ExplicitSpecialization)
     return DeclarationOnly;
 
-  if (hasExternalStorage())
+  if (!hasAttr<SelectAnyAttr>() && hasExternalStorage())
     return DeclarationOnly;
 
   // [dcl.link] p7:
   //   A declaration directly contained in a linkage-specification is treated
   //   as if it contains the extern specifier for the purpose of determining
   //   the linkage of the declared name and whether it is a definition.
-  if (isSingleLineLanguageLinkage(*this))
+  if (!hasAttr<SelectAnyAttr>() && isSingleLineLanguageLinkage(*this))
     return DeclarationOnly;
 
   // C99 6.9.2p2:
diff --git a/clang/test/CodeGen/ms-declspecs.c b/clang/test/CodeGen/ms-declspecs.c
index 328fc835d34..985c227faa3 100644
--- a/clang/test/CodeGen/ms-declspecs.c
+++ b/clang/test/CodeGen/ms-declspecs.c
@@ -5,6 +5,10 @@ const __declspec(selectany) int x2 = 2;
 // CHECK: @x1 = weak_odr global i32 1, comdat, align 4
 // CHECK: @x2 = weak_odr constant i32 2, comdat, align 4
 
+// selectany turns extern variable declarations into definitions.
+extern __declspec(selectany) int x3;
+// CHECK: @x3 = weak_odr global i32 0, comdat, align 4
+
 struct __declspec(align(16)) S {
   char x;
 };
diff --git a/clang/test/CodeGen/ms-declspecs.cpp b/clang/test/CodeGen/ms-declspecs.cpp
new file mode 100644
index 00000000000..f77c7cb8916
--- /dev/null
+++ b/clang/test/CodeGen/ms-declspecs.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -triple i386-pc-win32 %s -emit-llvm -fms-compatibility -o - | FileCheck %s
+
+// selectany turns extern "C" variable declarations into definitions.
+extern __declspec(selectany) int x1;
+extern "C" __declspec(selectany) int x2;
+extern "C++" __declspec(selectany) int x3;
+extern "C" {
+__declspec(selectany) int x4;
+}
+// CHECK: @"\01?x1@@3HA" = weak_odr global i32 0, comdat, align 4
+// CHECK: @x2 = weak_odr global i32 0, comdat, align 4
+// CHECK: @"\01?x3@@3HA"  = weak_odr global i32 0, comdat, align 4
+// CHECK: @x4 = weak_odr global i32 0, comdat, align 4