Index: llvm/include/llvm/ADT/StringRef.h
===================================================================
--- llvm/include/llvm/ADT/StringRef.h
+++ llvm/include/llvm/ADT/StringRef.h
@@ -13,6 +13,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
 #include <cassert>
 #include <cstring>
@@ -126,6 +127,18 @@
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     const char *data() const { return Data; }
 
+    /// Get a pointer to the start of the string, enforcing that it is null
+    /// terminated. This is intended to be used when the contract of the API is
+    /// to return a null terminated string.
+    const char *c_str() const {
+#if !defined(NDEBUG) || LLVM_ADDRESS_SANITIZER_BUILD ||                        \
+    LLVM_MEMORY_SANITIZER_BUILD
+      if (Data[size()] != '\0')
+        report_fatal_error("c_str() called on a non-null terminated string");
+#endif
+      return Data;
+    }
+
     /// empty - Check if the string is empty.
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool empty() const { return Length == 0; }