note that encodings could fail

docs/doxygen/overviews/string.h

@@ -236,7 +236,7 @@ arguments should take <tt>const wxString&</tt> (this makes assignment to the
 strings inside the function faster) and all functions returning strings
 should return wxString - this makes it safe to return local variables.
 
-Finally note that wxString uses the current locale encoding to convert any C string
+Note that wxString uses by default the current locale encoding to convert any C string
 literal to Unicode. The same is done for converting to and from @c std::string
 and for the return value of c_str().
 For this conversion, the @a wxConvLibc class instance is used.
@@ -248,6 +248,11 @@ is not appropriate for the current software and platform. The macro @c
 wxNO_IMPLICIT_WXSTRING_ENCODING disables all implicit conversions, and
 forces the code to explicitly indicate the encoding of all C strings.
 
+Finally note that encodings, either implicitly or explicitly selected,
+may not be able to represent all the string's characters. The result
+in this case is undefined: the string may be empty, or the
+unrepresentable characters may be missing or wrong.
+
 @code
 wxString s;
 // s = "world"; does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
@@ -255,12 +260,13 @@ s = wxString::FromAscii("world"); // Always compiles
 s = wxASCII_STR("world"); // shorthand for the above
 s = wxString::FromUTF8("world"); // Always compiles
 s = wxString("world", wxConvLibc); // Always compiles, explicit encoding
+s = wxASCII_STR("Grüße"); // Always compiles but encoding fails
 
 const char *c;
 // c = s.c_str();  does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
 // c = s.mb_str(); does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
-c = s.ToAscii(); // Always compiles
-c = s.ToUTF8(); // Always compiles
+c = s.ToAscii(); // Always compiles, encoding may fail
+c = s.ToUTF8(); // Always compiles, encoding never fails
 c = s.utf8_str(); // Alias for the above
 c = s.mb_str(wxConvLibc); // Always compiles, explicit encoding
 @endcode