Add a comment noting that raw_os_ostream does not check for errors.

llvm-svn: 75794

llvm/include/llvm/Support/raw_ostream.h

@@ -308,7 +308,8 @@ raw_ostream &errs();
 //===----------------------------------------------------------------------===//
 
 /// raw_os_ostream - A raw_ostream that writes to an std::ostream.  This is a
-/// simple adaptor class.
+/// simple adaptor class.  It does check for I/O errors; clients should use
+/// the underlying stream to detect errors.
 class raw_os_ostream : public raw_ostream {
   std::ostream &OS;