Re: [boost] Request for rationale

From: Gregory Dai (gregory.dai_at_[hidden])
Date: 2007-11-02 17:59:32

On 11/2/07, Mike Tegtmeyer <tegtmeye_at_[hidden]> wrote:
>
> I am often asked why shared_ptr always uses the custom deleter even when
> the pointer argument is zero. I know it is safe to delete a NULL pointer
> so this works with delete but it would seem that if the user is giving a
> custom deleter, then they are probably doing something else. ie
>
> //will crash if fread returns 0
> shared_ptr<FILE> foo(fread("foo.txt","r"),fclose);
>
> This is an easy screw-up for most new folks and the docs don't really
> explicitly point out this (I think) non-obvious behavior.
>
> One can obviously wrap the deleter with a check among numerous other
> things but I'm curious what the rationale was since this won't work "out
> of the box" with C APIs.  Can someone point me to the dialog discussing
> the design decision for this behavior so I can pass it along?

I don't think shared_ptr is designed to work on things like a FILE*. One
uses filestream or writes a simple class wrapping up the FILE*.