jjozwiak at qualcomm.com
Tue Jul 28 16:29:15 PDT 2009
Isn't the C++ "reference" annotation
char & x;
tantamount to declaration of a pointer
char * x;
to whom NULL assignment, as detectable at compile time, is a compile-time error?
If so, is that adequately applicable?
From: webkit-dev-bounces at lists.webkit.org [webkit-dev-bounces at lists.webkit.org] On Behalf Of Maciej Stachowiak [mjs at apple.com]
Sent: Tuesday, July 28, 2009 4:19 PM
To: Peter Kasting
Cc: WebKit Development
Subject: Re: [webkit-dev] NeverNull<T>
On Jul 28, 2009, at 3:59 PM, Peter Kasting wrote:
On Tue, Jul 28, 2009 at 3:55 PM, Oliver Hunt <oliver at apple.com<mailto:oliver at apple.com>> wrote:
Personally i like the idea of having type system/compiler enforced null checking.
Note that eseidel's proposal is still a runtime check. One could use template specialization to write a class that gives a compile-time error if you try to assign NULL directly to a pointer, but I'm not enough of a template wizard to know if it could be made to catch all types of assignment (e.g. if you could catch that when a NeverNull<Foo> is initialized by an existing Foo*, that existing pointer must not contain NULL).
I don't think you can make the C++ type system prevent pointers from having null values without a runtime check. Any raw pointer expression could have a null value and this is not visible at compile time. It might be possible to prevent direct assignment of 0, which would provide at least a little bit of static checking.
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