safety: null checks

ag0aep6g anonymous at
Mon Nov 23 01:26:15 UTC 2020

On Monday, 23 November 2020 at 00:50:03 UTC, Ola Fosheim Grostad 
> Well, the spec said that the value should be valid, which null 
> by definition should not have, then the example comment 
> mentioned a well defined crash which is a contradiction in 
> terms.
> So the spec is unsound.

I wrote that part of the spec. My intent was to define null as a 
safe value. For other pointer-like types I wrote: "A [thing] is 
safe when it is `null` or [whatever]". Please feel free to add 
that phrase for pointers, too, or adjust the text in any other 
way that makes it more clear that null is a safe value.

> What you would require from a high level language is that 
> dereferencing null pointers is caught either at compile time or 
> at runtime. But that is slow on some platforms. So this is just 
> an example of the implementation being the spec, and actual 
> document does not make sense in a general setting.

The reference implementation treats null as a safe value. Yes, 
that can imply additional checks at run time. That's what Walter 
chose, for better or worse.

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