Mail Archives: djgpp/1996/10/14/19:51:11
In article <325FE9B3 DOT 13AB AT cs DOT com>, John M. Aldrich <fighteer AT cs DOT com> wrote:
>mrichman AT cybernex DOT net wrote:
>> Is it safe to assume that all pointer variables take up the same
>> number of bytes, or is that compiler dependent.
>16-bit compilers will use 16-bit pointers, and 32-bit compilers will use
>32-bit pointers.
Untrue; most 16-bit compilers for the x86 offer a choice of 16-bit
pointers (small model) or 24-bit pointers (stored in 32-bits as
segment:offset; large model).
Anyway, I read the question not as: "do different platforms have the same
size pointers?" (pretty obviously not true), but as "on a given
platform, will pointers to different types of objects be the same size?"
And the answer is: not necessarily--though you'll have to search long
and hard to find an exception, the standard makes no such guarantee.
>Remember, ANSI only provides that short <= int <= long, but does not
>dictate the size of int.
True, but I don't see the relevance.
>Pointers are almost always int-sized, so you can't assume anything about them.
Completely false! The size of a pointer is usually based on the size of
the address bus, the size of an int on the size of the data bus.
Most compilers for the x86 are 16-bit, and offer small and large memory
models. Since the small model is useless for all but the simplest
programs, that means that for most programs on the most common platform
in the world, pointers are not int-sized. OTOH, the question was asked
in c.o.m.djgpp for some strange reason. With djgpp, pointers *are*
int-sized, but, further, you *can* assume something about the size of
ints!! :)
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