[boost] Re: [wave] cw-8.3 segfault..

From: David Abrahams (dave_at_[hidden])
Date: 2005-05-17 10:22:15

Hartmut Kaiser <hartmut.kaiser_at_[hidden]> writes:

>  
> David Abrahams wrote:
>
>> > This I don't understand anymore. The code in question is:
>> >
>> >     some_spirit_grammar g;
>> >     boost::spirit::pt_parse(it, end, g);
>> >
>> > the programm crashes inside pt_parse because of g == 0xcccccccc 
>> > (destroyed object), where pt_parse takes 'g' by const reference. 
>> > Initially 'g' was defined as a function local static 
>> instance, which 
>> > I've removed now because I had the suspicion CW8.x couldn't 
>> handle that correctly.
>> >
>> > Any clues?
>> > Regards Hartmut
>> 
>> Are you running into the CW 8.3 "CRTP bug" where casting to a 
>> derived class reference can induce a copy?
>
> That's possible, since Spirit passes the parser<> base class around and
> casts it to the correct derived class (type supplied through CRTP) when
> needed. Is there a known workaround?

Yes, use 

  *static_cast<Derived*>(this) 

instead of

  static_cast<Derived&>(*this)

> OTOH all the Spirit tests should fail if this assumption is correct.

I wouldn't count on it.  Temporaries can be deceptive.  The memory may
remain valid after destruction.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com