"Jeff Williams" <jwilliams@mfchelp.com> wrote in message news:20040820121228.RIND12967.fep02.biz.rr.com@[127.0.0.1]...

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Date: Thu, 19 Aug 2004 21:09:07 -0400 From: "Joe Gottman" <jgottman@carolina.rr.com> Subject: [boost] shared_ptr feature request: void_pointer_cast

I know this isn't the best time to request a new feature, but I just had an idea for an extremely useful new function for shared_ptr. It is common to use a shared_ptr<void> in places where a void * would otherwise be used. While a void * can point to anything, there is no safe way to determine at run-time what type it originally pointed to. Casting it to the wrong type can result in undefined behavior.

How is this idea any different that just using boost::shared_ptr<boost::any> ?

shared_ptr<void> is interoperable with shared_ptr<X> for all non-const X. If you want to use shared_ptr<boost::any>, whoever creates the original shared_ptr has to declare it as type shared_ptr<boost::any>. With shared_ptr<void> you can take a type-safe shared_ptr<int> (which may have been created by third-party code), pass it to non-type-safe code that uses shared_ptr<void>, then later regain type safety by using void_pointer_cast. Joe Gottman.