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Date: Wed, 21 Nov 2012 20:18:00 -0000
From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: Tom Tromey <tromey@redhat.com>, gdb@sourceware.org
Subject: Re: Will therefore GDB utilize C++ or not?
Message-ID: <20121121201805.GA1709@host2.jankratochvil.net>
References: <20120330161403.GA17891@host2.jankratochvil.net> <87aa2rjkb8.fsf@fleche.redhat.com> <4F832D5B.9030308@redhat.com> <20120409190519.GA524@host2.jankratochvil.net> <4F833D29.4050102@redhat.com> <8762cwpz3u.fsf@fleche.redhat.com> <4FBA6D04.7060804@redhat.com>
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On Mon, 21 May 2012 18:27:48 +0200, Pedro Alves wrote:
> What I meant by not that different, is, that with RAII you get
> to write something like (the dumbest version of a RAII object
> that supports canceling possible):
> 
> class my_raii_thing
> {
> private:
>    whatever_arg *arg; << moral equivalent of the cleanup args.
>    bool discarded;
> 
> public:
>    my_raii_thing (whatever_arg *p) : arg (p), discarded(false)
>    {}
> 
>    ~my_raii_thing () << moral equivalent of a cleanup function.
>    {
>       if (!discarded)
>         {
>           // whatever to release this->arg or something like that.
>         }
>    }
> 
>    void discard ()
>    {
>       discarded = true;
>    }
> };
> 
> and then do:
> 
>   my_raii_thing foo (&whatever_arg);
> 
>   if (whatnot)
>     {
>        whatever_arg.discard();
>        return SUCESS;
>     }
>   }

I find it too complicated, why not just shared_ptr:

#include <memory>
#include <iostream>
using namespace std;
class R {
public:
  R() { cout << "R new" << endl; }
  ~R() { cout << "R delete" << endl; }
  string val() { return "isR"; }
};
static shared_ptr<R> getR(bool fail) {
  auto v=shared_ptr<R>(new R());
  if (fail)
    throw fail;
  return v;
}
int main() {
  try {
    getR(true);
  } catch (...) {}
  cout << getR(false)->val() << endl;
}

R new
R delete
R new
isR
R delete


As C++11 dependency is probably too strict one can use Boost instead and as GDB
does not like external dependencies stripped down Boost can be bundled to the
sourceware repository - on normal systems sure C++11 libraries get used instead.


Jan