Implement support for the -undef command line option, patch by
Roman Divacky! PR5363


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85932 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Preprocessor/macro_undef.c b/test/Preprocessor/macro_undef.c
new file mode 100644
index 0000000..4507cdd
--- /dev/null
+++ b/test/Preprocessor/macro_undef.c
@@ -0,0 +1,4 @@
+// RUN: clang-cc -dM -undef -Dfoo=1 -E %s | FileCheck %s
+
+// CHECK-NOT: #define __clang__
+// CHECK: #define foo 1