[Bug c++/81239] New: std::__cxx11::string& visible in gcc warning output

["jg at jguk dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81239

            Bug ID: 81239
           Summary: std::__cxx11::string& visible in gcc warning output
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jg at jguk dot org
  Target Milestone: ---

Created attachment 41643
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41643&action=edit
Example

Hello

Can G++ just not say __cxx11 in warning example main.cpp:18:17 below ?

I noticed that with, or without -std=c++11 on gcc params, the output of
std::string for references still shows __cxx11. for const ref, it isn't shown
in the warning.  

The later warning is ok main.cpp:10:6

Warnings:

$ g++ -Wall -o main main.cpp
main.cpp: In function ‘int main()’:
main.cpp:18:17: error: too few arguments to function ‘void test_params(const
string&, std::__cxx11::string&)’
     test_params();
                 ^
main.cpp:10:6: note: declared here
 void test_params(const string & mystr1, string & out_str)
      ^



Expected:

main.cpp:18:17: error: too few arguments to function ‘void test_params(const
string&, string&)’
     test_params();