Subject: Re: [boost] [smart_ptr] Interest in the missing smart pointer (that can target the stack)
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2016-01-29 16:27:01
On Fri, Jan 29, 2016 at 11:24 AM, Rob Stewart <rob.stewart_at_[hidden]>
wrote:
> I understand that full well. The example that Emil presented can easily
> lead to having shared_ptrs that refer to release stack memory.
>
My original example was:
{
foo local;
shared_ptr<foo> pl(&local,null_deleter());
....
do_something(p);
....
assert(pl.unique());
}
What if I change it to:
int main()
{
foo local;
shared_ptr<foo> pl(&local,null_deleter());
....
do_something(p);
....
assert(pl.unique());
}
Does it look less scary now?
It seems that you guys look at this as "why would do_something take a
shared_ptr if it can't keep a copy of it". Being able to retain a copy of
the shared_ptr is one reason, yes. The other reason is that do_something
needs to make sure that the object doesn't expire before it returns, which
in this case it doesn't.
Further, what if do_something is declared as:
void do_something( weak_ptr<foo> const & );
Now it's not that it'll keep shared_ptr references after it returns, but
it'll be creating and destroying shared_ptrs as needed, to make sure that
the object doesn't expire while it's being used. Which, again, in this case
it doesn't.
Emil