Index: clang/docs/analyzer/checkers.rst
===================================================================
--- clang/docs/analyzer/checkers.rst
+++ clang/docs/analyzer/checkers.rst
@@ -319,13 +319,20 @@
 """""""""""""""""""""""""""""
 Checks std::string operations.
 
+The current implementation is very limited. It only checks if the cstring
+pointer from which the ``std::string`` object is constructed is ``NULL`` or not.
+If it cannot reason about the nullness of the pointer it will assume that it
+was non-null to satisfy the precondition of the constructor.
+
+One should never construct ``std::strings`` from ``NULL`` pointers.
+
 .. code-block:: cpp
 
  #include <string>
 
  void f(const char *p) {
    if (!p) {
-     std::string msg(p); // warn: p is NULL
+     std::string msg(p); // warn: The parameter must not be null
    }
  }