Re: [boost] Deleter's nothrow copy-constructor

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-09-23 06:24:24

From: "David Abrahams" <dave_at_[hidden]>
> The smart pointers docs say:
>
> The requirement that the copy constructor of D does not throw is too
> strong. It will be removed when some core language issues are resolved
> (cv-qualified function types, partial ordering clarifications.)]
>
> Can you explain where that requirement comes from?

The requirement comes from the pass by value. If the copy constructor
throws, the pointer is leaked. Removing the requirement requires a pass by
(const) reference. The problems are that (1) pass by value conveniently
changes functions (function references) to function pointers (this has to be
performed manually otherwise and some compilers may not be able to do it)
and (2) const references don't currently (per the standard) bind to
functions. This can be solved (I think) but it requires an overload set that
breaks on many compilers due to 14.5.5.2 problems (and of course it will
break on compilers that don't do partial ordering at all.)

I'll revisit the issue eventually, but it's not currently a priority.