c++ - Syntax for converting expired weak_ptr<T> to shared_ptr<T> -

from i've read, shared_ptr<t> not de-allocated until both strong references , weak references dropped.

i understand shared object considered expired when there no more strong references it. standard lock() function of weak_ptr<t> therefore fails in such case because object considered 'expired'.

however, if deleter of shared pointer overridden such managed object not deleted, should valid generated shared_ptr<t> weak_ptr<t> - cannot find right syntax this.

std::shared_ptr<int> s_ptr(new(42), d()); std::weak_ptr<int) w_ptr(s_ptr); s_ptr.reset();  s_ptr = std::shared_ptr<int>(w_ptr, false); 

edit

to clarify bit further, i'm trying construct object pool of re-usable shared_ptr<t>. reason behind because every use of shared_ptr results in 1 or more heap memory allocations. i've added deleter every shared_ptr<t> stores weak_ptr<t> reference such deleter gets called should able re-add pool of available shared_ptr<t> objects (with managed object intact). keeping weak_ptr<t> stored inside shared_ptr<t>'s deleter, therefore shouldn't stop deleter being called.

the end goal obtain smart pointer doesn't consisant heap allocation - or @ least small number.

from i've read, shared_ptr not de-allocated until both strong references , weak references dropped.

wrong. std::shared_ptr has 2 blocks - control block contains reference counts, etc, block actual data.

when shared count goes 0, data block (usually) deallocated. why illegal make std::shared_ptr expired std::weak_ptr.

on note, why ever want functionality? ruins entire point of std::weak_ptr, able "store" pointer object stored std::shared_ptr without incrementing reference count. if want that, please use std::shared_ptr