size_t + ptrdiff_t

[Manu]

On 19 February 2012 17:09, Stewart Gordon <smjg_1998 at yahoo.com> wrote:

> On 19/02/2012 14:59, Manu wrote:
>
>> Okay, so it came up a couple of times, but the questions is, what are we
>> going to do about it?
>>
>> size_t and ptrdiff_t are incomplete, and represent non-complimentary
>> signed/unsigned
>> halves of the requirement.
>> There are TWO types needed, register size, and pointer size. Currently,
>> these are assumed
>> to be the same, which is a false assumption.
>>
>
> The whole point of size_t and ptrdiff_t is that they are integer types
> that span the address space.  So that the size of an allocated block of
> memory (and consequently, the number of elements in an array) is bound to
> fit in a size_t, and the displacement between two memory locations is bound
> to fit in a ptrdiff_t.
>
> What would this "register size" type you are proposing be for, exactly?
>

You also need a type that knows the native word size of the machine, not
just a pointer width. If size_t should be the pointer size, then there
needs to be some other type that specifies the register width of the
architecture.


> <snip>
>
>  There is also the problem that there is lots of code written using the
>> incorrect types.
>>
> <snip>
>
> Like what?
>

There is code that assumes size_t is the width of the pointer, and other
code that assumes size_t is the width of the native int. Only one of those
is correct, whichever you declare it to be, and another type needs to be
invented to define the other.
It is common that pointers are the same width as the int regs, but there
are many architectures where it's not true.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puremagic.com/pipermail/digitalmars-d/attachments/20120219/07e9c77c/attachment-0001.html>