1 files changed, 27 insertions, 0 deletions
diff --git a/test/Modules/macro-redefinition.cpp b/test/Modules/macro-redefinition.cpp
new file mode 100644
index 0000000000000..7b1c7b6586242
--- /dev/null
+++ b/test/Modules/macro-redefinition.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -fmodules -x c++-module-map %s -fmodule-name=__usr_include -verify
+// RUN: %clang_cc1 -fmodules -x c++-module-map %s -fmodule-name=__usr_include -verify -DIMPORT
+
+module __usr_include {
+  module stddef {}
+  module stdlib {}
+}
+
+#pragma clang module contents
+
+// expected-no-diagnostics
+
+#pragma clang module begin __usr_include.stddef
+  #define NULL 0
+#pragma clang module end
+
+#pragma clang module begin __usr_include.stdlib
+  #ifdef IMPORT
+    #pragma clang module import __usr_include.stddef
+  #else
+    #pragma clang module begin __usr_include.stddef
+      #define NULL 0
+    #pragma clang module end
+  #endif
+
+  void *f() { return NULL; } // ok, NULL is visible here
+#pragma clang module end