How to test for duplicate error messages

[Volker Reichelt]

Hi,

I've got some questions regarding duplicate error messages in the testsuite:

How do I test that an error mesage isn't emitted twice
(like in g++.dg/parse/dtor2.C )?

I could only find g++.dg/other/error8.C which isn't working as expected
IMHO. The last three lines read

  // The duplicated error messages are xfailed for now (tracked in the PR)
  // { dg-bogus "" "duplicate error messages" { target *-*-* } 8 }
  // { dg-bogus "" "duplicate error messages" { target *-*-* } 9 }

But
* the tests do PASS (it's not an XPASS!)
* the PR was closed
* trying to copy such a line to g++.dg/parse/dtor2.C didn't work
  (I got PASS although there's a duplicate message).

So the questions are:
* How to check for duplicate error messages?
* How to fix g++.dg/other/error8.C ?

Regards,
Volker