Just a friendly reminder about using arrays in boolean conditions

[Steven Schveighoffer]

On Saturday, 23 November 2024 at 00:57:01 UTC, kdevel wrote:
> On Sunday, 17 November 2024 at 22:17:18 UTC, Steven 
> Schveighoffer wrote:
>> On Sunday, 17 November 2024 at 21:50:18 UTC, kdevel wrote:
>>> My question is: Is it possible that a valid D program gets 
>>> into a
>>> state where an array has ptr == null and length > 0? If so, 
>>> how?
>>
>> Yes, the compiler uses it:
>>
>> ```d
>> [...]
>>     auto i = typeid(S).initializer;
>> [...]
>> ```
>
> Issue 20722 - typeid(X).initializer() breaks safety
> https://issues.dlang.org/show_bug.cgi?id=20722

Indeed, I don't think this should be considered safe. I don't 
know how much code would break to change it to system.

But this is beside the point that I was trying to make -- that 
this scenario does actually ahppen.

You can think of it as a storage of a pointer, which if null 
means "all are zero", and a length, which is the number of bytes 
in the initializer.

It is used in places where only TypeInfo is available. I believe 
this is mostly for AA and array runtime, and nothing else. 
Eventually we will be able to remove these dependencies.

-Steve