Re: [boost] Proposed new RAII Library

Subject: Re: [boost] Proposed new RAII Library
From: Krzysztof Czainski (1czajnik_at_[hidden])
Date: 2012-09-17 05:13:43

2012/9/16 Peter Dimov <lists_at_[hidden]>:
> On 12-09-16 9:35 AM, Krzysztof Czainski wrote:
>>
>> So, maybe the dismiss functionality can be an external function
>> (assuming a guard can be rebound to another function):
>>
>> void do_nothing() {}
>> void dismiss( guard& ) { guard = do_nothing; }
>
>
> guard::operator=( guard const& ), if it exists, should probably execute the
> stored function before replacing it. To see why, consider:
>
> struct X
> {
>    guard g_;
>    FILE* f_;
>
>    explicit X( FILE* f ): g_( fclose, f ), f_( f ) {}
> };
>
> and think what happens in X::operator=( X const& ).
>
> dismiss() is different - it's the equivalent of auto_ptr::release (not of
> auto_ptr::op= or reset).
>
> And yes, I do see that the above example uses guard::op=( F f ), not the
> copy assignment, but it wouldn't be very consistent for the two to differ in
> such a fundamental way.

Right, I missed that.

So dismiss(g) should not be implemented in terms of operator=, but it
still can be an external function replacing the internal function with
do_nothing. But maybe this point shows, that dismiss belongs inside
class guard.

Kris