Re: [boost] [smart_ptr] shared_from_this

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-03-26 11:24:18

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On Wednesday 26 March 2008 11:08 am, Daniel Frey wrote:
> But shared_from_this() requires that there must exist at least one
> shared_ptr instance that owns the object, which means that the
> use_count() is always guaranteed to be >0, hence the exception is never
> thrown by shared_ptr's ctor.

The exception is thrown if the user violates the requirement.  Actually, on 
the svn trunk the requirement is looser, shared_from_this can be called 
before a shared_ptr has taken ownership (the docs haven't been updated to 
reflect that though).  It's still possible to throw though, if the object 
outlives the shared_ptrs that own it.

> Oh, and the ctor of shared_ptr therefore *can* throw something else than
> std::bad_alloc, right?

Yes, and it says so in the constructor's documentation.  I'm not familiar with 
the precise rules of C++ language specification-ese, so I don't know if the 
blanket statement about the classes' "functions" in the intro also applies to 
constructors?

- -- 
Frank
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