libclang: document the purpose of createNull()
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174195 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CXString.h b/tools/libclang/CXString.h
index 0495ee9..0688712 100644
--- a/tools/libclang/CXString.h
+++ b/tools/libclang/CXString.h
@@ -29,6 +29,8 @@
CXString createEmpty();
/// \brief Create a CXString object for an NULL string.
+///
+/// A NULL string should be used as an "invalid" value in case of errors.
CXString createNull();
/// \brief Create a CXString object from a C string.