Why does nobody seem to think that `null` is a serious problem in D?

[Johan Engelen]

On Wednesday, 21 November 2018 at 07:47:14 UTC, Jonathan M Davis 
wrote:
>
> IMHO, requiring something in the spec like "it must segfault 
> when dereferencing null" as has been suggested before is 
> probably not a good idea is really getting too specific 
> (especially considering that some folks have argued that not 
> all architectures segfault like x86 does), but ultimately, the 
> question needs to be discussed with Walter. I did briefly 
> discuss it with him at this last dconf, but I don't recall 
> exactly what he had to say about the ldc optimization stuff. I 
> _think_ that he was hoping that there was a way to tell the 
> optimizer to just not do that kind of optimization, but I don't 
> remember for sure.

The issue is not specific to LDC at all. DMD also does 
optimizations that assume that dereferencing [*] null is UB. The 
example I gave is dead-code-elimination of a dead read of a 
member variable inside a class method, which can only be done 
either if the spec says that`a.foo()` is UB when `a` is null, or 
if `this.a` is UB when `this` is null.

[*] I notice you also use "dereference" for an execution machine 
[**] reading from a memory address, instead of the language doing 
a dereference (which may not necessarily mean a read from memory).
[**] intentional weird name for the CPU? Yes. We also have D code 
running as webassembly...

-Johan