Re: [xmlvm-dev] byte sign

[Arno P. <ar...@pu...>]

A byte is a signed 8 bit value that needs to be sign-extended to 32
bits when loaded into a register.

Arno

On Apr 5, 2011, at 3:30 PM, Panayotis Katsaloulis
<pan...@pa...> wrote:

>
> On Apr 5, 2011, at 8:49 PM, Arno Puder wrote:
>
>>
>> things are a little trickier. According to section 2.4.1 of the Java
>> Specs: "The integral types are byte, short, int, and long, whose values
>> are 8-bit, 16-bit, 32-bit, and 64-bit signed two's-complement integers,
>> respectively, and char, whose values are 16-bit unsigned integers
>> representing Unicode characters"
>>
>> Then in Section 3.11.1 of the Java spec it says: "Note that most
>> instructions in Table 3.2 do not have forms for the integral types byte,
>> char, and short. None have forms for the boolean type. Compilers encode
>> loads of literal values of types byte and short using Java virtual
>> machine instructions that sign-extend those values to values of type int
>> at compile time or run time. Loads of literal values of types boolean
>> and char are encoded using instructions that zero-extend the literal to
>> a value of type int at compile time or run time."
>>
>> So, you are correct that a byte is a signed 8-bit value, however it
>> needs to be properly sign extended. In the C backend I already use
>> typedef's consistently, so it should be easy to fix. The Objective-C
>> backend is not as cleanly implemented.
>>
>> Arno
>>
>
>
> So, the problem remains, should "byte" be a signed or unsigned char under ObjC backend, and especially in the Byte methods?
> My understanding is that it is sometimes a signed integer, but in any case, it is *not* an unsigned char.
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