Index: clang/lib/Frontend/InitPreprocessor.cpp
===================================================================
--- clang/lib/Frontend/InitPreprocessor.cpp
+++ clang/lib/Frontend/InitPreprocessor.cpp
@@ -778,6 +778,20 @@
     }
   }
 
+  // macros to help identify the narrow and wide character sets
+  // NOTE: clang currently ignores -fexec-charset=. If this changes,
+  // then may need to change.
+  Builder.defineMacro("__clang_literal_encoding__", "\"UTF-8\"");
+  if (TI.getTypeWidth(TI.getWCharType()) >= 32) {
+    // NOTE: 32-bit wchar_t signals UTF-32. This may change if 
+    // -fwide-exec-charset= is ever supported.
+    Builder.defineMacro("__clang_wide_literal_encoding__", "\"UTF-32\"");
+  } else {
+    // NOTE: Less-than 32-bit wchar_t generally means UTF-16 (e.g., Windows, 32-bit IBM).
+    // This may change if -fwide-exec-charset= is ever supported.
+    Builder.defineMacro("__clang_wide_literal_encoding__", "\"UTF-16\"");
+  }
+
   if (LangOpts.Optimize)
     Builder.defineMacro("__OPTIMIZE__");
   if (LangOpts.OptimizeSize)
Index: clang/test/Preprocessor/init.c
===================================================================
--- clang/test/Preprocessor/init.c
+++ clang/test/Preprocessor/init.c
@@ -119,6 +119,8 @@
 // COMMON:#define __clang_minor__ {{[0-9]+}}
 // COMMON:#define __clang_patchlevel__ {{[0-9]+}}
 // COMMON:#define __clang_version__ {{.*}}
+// COMMON:#define __clang_literal_encoding__ {{.*}}
+// COMMON:#define __clang_wide_literal_encoding__ {{.*}}
 // COMMON:#define __llvm__ 1
 //
 // RUN: %clang_cc1 -E -dM -triple=x86_64-pc-win32 < /dev/null | FileCheck -match-full-lines -check-prefix C-DEFAULT %s