Merge templated static member variables, fixes http://llvm.org/pr26179.

Patch by Vassil Vassilev!
Reviewed by Richard Smith.

llvm-svn: 258524

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -2595,8 +2595,24 @@ static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
   // Variables with the same type and linkage match.
   if (VarDecl *VarX = dyn_cast<VarDecl>(X)) {
     VarDecl *VarY = cast<VarDecl>(Y);
-    return (VarX->getLinkageInternal() == VarY->getLinkageInternal()) &&
-      VarX->getASTContext().hasSameType(VarX->getType(), VarY->getType());
+    if (VarX->getLinkageInternal() == VarY->getLinkageInternal()) {
+      ASTContext &C = VarX->getASTContext();
+      if (C.hasSameType(VarX->getType(), VarY->getType()))
+        return true;
+
+      // We can get decls with different types on the redecl chain. Eg.
+      // template <typename T> struct S { static T Var[]; }; // #1
+      // template <typename T> T S<T>::Var[sizeof(T)]; // #2
+      // Only? happens when completing an incomplete array type. In this case
+      // when comparing #1 and #2 we should go through their elements types.
+      const ArrayType *VarXTy = C.getAsArrayType(VarX->getType());
+      const ArrayType *VarYTy = C.getAsArrayType(VarY->getType());
+      if (!VarXTy || !VarYTy)
+        return false;
+      if (VarXTy->isIncompleteArrayType() || VarYTy->isIncompleteArrayType())
+        return C.hasSameType(VarXTy->getElementType(), VarYTy->getElementType());
+    }
+    return false;
   }
 
   // Namespaces with the same name and inlinedness match.

clang/test/Modules/Inputs/PR26179/A.h

@@ -0,0 +1,4 @@
+#include "basic_string.h"
+#include "B.h"
+
+int *p = a;

clang/test/Modules/Inputs/PR26179/B.h

@@ -0,0 +1,2 @@
+#include "basic_string.h"
+extern int a[5];

clang/test/Modules/Inputs/PR26179/basic_string.h

@@ -0,0 +1,14 @@
+#ifndef _GLIBCXX_STRING
+#define _GLIBCXX_STRING 1
+
+template<typename T>
+struct basic_string {
+  static T _S_empty_rep_storage[];
+};
+
+template<typename T>
+T basic_string<T>::_S_empty_rep_storage[sizeof(T)];
+
+extern int a[];
+
+#endif

clang/test/Modules/Inputs/PR26179/module.modulemap

@@ -0,0 +1,9 @@
+module A {
+  header "A.h"
+  export *
+}
+
+module B {
+  header "B.h"
+  export *
+}

clang/test/Modules/pr26179.cpp

@@ -0,0 +1,7 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -I%S/Inputs/PR26179 -verify %s
+// RUN: %clang_cc1 -fmodules -fmodule-map-file=%S/Inputs/PR26179/module.modulemap -fmodules-cache-path=%t -I%S/Inputs/PR26179 -verify %s
+
+#include "A.h"
+
+// expected-no-diagnostics