Getting action on your favorite D issues

[Avrina]

On Saturday, 6 June 2020 at 15:36:07 UTC, Patrick Schluter wrote:
> On Saturday, 6 June 2020 at 14:34:11 UTC, Avrina wrote:
>> On Saturday, 6 June 2020 at 10:09:07 UTC, Patrick Schluter 
>> wrote:
>>> On Friday, 5 June 2020 at 23:53:28 UTC, H. S. Teoh wrote:
>>>> Output:
>>>> -----------------
>>>> dead
>>>> -----------------
>>>>
>>>> Truly, DMD's backend is in the bright future of strange and 
>>>> wonderful quantum effects, whereas LDC is clearly still 
>>>> stuck in the antiquated classical past. ;-)
>>>>
>>> Sorry, but undefined behaviour is undefined behaviour. The 
>>> dmd code generator is not at fault here.
>>
>> With statements like this I always feel like people don't 
>> understand what "undefined behavior" means.
>>
>> All the void initializer does is not initialize the memory of 
>> the bool. DMD is testing more than a single bit for a type 
>> that is only a single bit, it flip flops between testing a 
>> byte and testing a bit. That is most definitely a bug in the 
>> DMD backend.
>
> Then it is also a bug in llvm and gcc as they generate the code 
> under exactly the same assumption that a bool is 1 or 0 (and 
> that in C, C++ and D).
> Only in contexts where there is int promotion is all the word 
> checked.

No, that's why LDC doesn't have the same issue. D is suppose to 
be better than C and C++, so saying its broken in C and C++ so D 
should be broken too isn't a very convincing argument.

The issue is that DMD isn't consistent. Like I said before, it 
flip flops between checking a single bit and 8 bits.


> This has nothing to do with the D frontend, #pure or whatnot. 
> It's a pure backend code generation assumption.
> If the frontend violates that assumption, it is an issue of the 
> frontend.

Which is why I said its an issue with the backend.

>>
>> Just to bring up an old debate, this has been argued to not be 
>> a bug and is defined behavior and *will not* be changed.
>>
>>   void foo(bool);
>>   void foo(byte);
>>
>>   foo(0); // calls bool
>>   foo(1); // calls bool
>>   foo(2); // calls byte
>
> This has nothing to do with the issue at hand.
> This it's a technical choice. It might be surprising, it is 
> very likely a wrong choice, but it is not violation of the 
> assumption of the backend (even if it a violation of the 
> programmer).

I know it doesn't. The point was that book is treated as a 1-bit 
integer, and DMDs backend treats it like a byte (sometimes).