implicit ubyte casting

Jeremie Pelletier jeremiep at
Fri Oct 2 06:56:42 PDT 2009

Don wrote:
> Saaa wrote:
>> Jeremie Pelletier wrote
>>> Saaa wrote:
>>>> I think is very bug-prone, isn't it obvious iub should be -5?
>>>> ubyte ub = 5;
>>>> int iub = -ub; // iub now is 251
>>>> What is the reasoning to do it this way?
>>> Minus toggles the most significant bit, be it on a signed or unsigned 
>>> type. When converting it to an int, the byte being signed or unsigned 
>>> does make a difference: when unsigned the number is copied as is, 
>>> when signed the most significant bit (bit 7) is shifted to the most 
>>> significant bit of the int (bit 31).
>>> Its therefore pretty standard logic, no warning is given since the 
>>> entire ubyte range fits within an int
>>> Jeremie
>> Thanks, but it is not that I do not know how it occurs more that
>> I should have asked whether people use this kind of logic.
>> For me it resulted in annoying bug like this:
>> for(int i = nloop;i<10;i++);//ubyte nloop is created quite a few lines 
>> above.
> This has been discussed before, and it really should be an error.
> It's reasonable to implicitly cast between integral types of different 
> size, and also signed<->unsigned, but performing both within the same 
> expression is almost always a bug. It should not be possible without an 
> explicit cast.

I know VC++ shouts a warning everytime signed and unsigned integrals are 
mixed, maybe that's the road D should take too.

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