Re: [boost] [ptr_container] Questionable strong guarantee of ptr_map::insert()

Subject: Re: [boost] [ptr_container] Questionable strong guarantee of ptr_map::insert()
From: Jeffrey Bosboom (jbosboom_at_[hidden])
Date: 2009-08-25 00:12:27

Edward Diener wrote:
> Nevin ":-]" Liber wrote:
>> I believe
>> that most
>> people expect that if they pass an auto_ptr and an exception is 
>> thrown, then
>> the auto_ptr has not relinquished ownership.  Otherwise, why bother 
>> with an
>> auto_ptr at all?
> 
> I would have assumed that if I pass an auto_ptr that ownership is 
> relinquished no matter what happens later, exception or not. Is not that 
> how the copy constructor of an auto_ptr is supposed to work ?

I agree -- auto_ptr's copy constructor has move semantics, and the copy 
(move) must be made before the function is entered (arguments can be 
evaluated in any order, but there's a sequence point before entering the 
function body).

For the record, if the argument was an auto_ptr&, I would expect the 
auto_ptr to still own the resource if an exception was thrown, although 
I don't know how to implement it (moving back into the auto_ptr might 
throw too).

--Jeffrey Bosboom