Re: [RFA] Remove VEC from breakpoint

[Simon Marchi <simark@simark.ca>]

On 2018-07-09 12:21 AM, Tom Tromey wrote:
> Tom> I'm going to take another attempt at it, using a hack to get the
> Tom> configure logging output into the file that's visible in buildbot,
> Tom> since I didn't see a way to fetch the config.log.
> 
> That didn't take long:
> 
> https://gdb-build.sergiodj.net/builders/Debian-s390x-native-gdbserver-m64/builds/5859/steps/compile%20gdb/logs/stdio
> 
> I don't know what is going on here, but basically the test case passes
> fine in configure, but causes problems in the build.
> 
> configure's test is:
> 
>     struct Bar { virtual ~Bar() {} }; Bar getbar();
>     int
>     main ()
>     {
>     const Bar& b = getbar();
>       ;
>       return 0;
>     }
> 
> But the real code is:
> 
>   scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
> 
> If you have any ideas, I'd appreciate it.  Perhaps it's really some
> different bug.  This only seems to affect the s390 builders.
> 
> Tom
> 

Hi Tom,

I reduced the case to this:

  struct scoped_restore_base {};

  struct scoped_restore_tmpl : public scoped_restore_base {
    ~scoped_restore_tmpl() {}
  };

  void func() {
    const scoped_restore_base & save_inferior_ptid = scoped_restore_tmpl();
  }

The type of "save_inferior_ptid" seems important.  If it's a reference to the
child class, we don't get the warning with g++ 4.9.  So your configure test would
need to have that.  g++ 4.9 is available in Debian 8, which you can easily run in
a docker container.

root@9305ed73237c:/gdb/gdb# g++ --version
g++ (Debian 4.9.2-10+deb8u1) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

root@9305ed73237c:/gdb/gdb# g++ -std=gnu++11 -Werror -c -o repro.o -Wunused-variable  repro2.cpp
repro2.cpp: In function 'void func()':
repro2.cpp:8:31: error: unused variable 'save_inferior_ptid' [-Werror=unused-variable]
   const scoped_restore_base & save_inferior_ptid = scoped_restore_tmpl();
                               ^
cc1plus: all warnings being treated as errors

Simon