[boost] [smart_ptr] enable_shared_from_this enhancement

From: Frank Mori Hess (fmhess_at_[hidden])
Date: 2008-03-17 01:36:34

I'm curious a patch to boost::enable_shared_from_this that makes 
shared_from_this() work inside constructors would be considered?

The implementation I've got in mind (haven't actually tried it yet) would 
work as follows.  I'd add two shared_ptrs to enable_shared_from_this, call 
them "internal_shared" and "external_shared".  external_shared would be 
assigned the external shared_ptr which first takes ownership of *this.  
internal_shared would be initialized with the "this" pointer, and a custom 
deleter which would reset external_shared.  internal_shared would be reset 
right after external_shared is initialized (when an external shared_ptr 
takes ownership of *this).  Any calls to shared_from_this() that occur 
prior to an external shared_ptr taking ownership of *this (such as in the 
constructor) would get a copy of internal_shared.

So the idea is, external_shared would keep the object alive as long as any 
copies of internal_shared that got made in the constructor are still 
around.

-- 
Frank