C Language, Long as array/pointer address

Rui M. Perei
#1 / 4

Long as array/pointer address

I'd like to do the following:

long index = 10;;
char *string = "This is a test string";

printf("%c\n", string[index]);
printf("%c\n", *(string + index));

but when I compile the above in a 16bit compiler (haven't tried it on a
32bit compiler), the compiler apparently casts the index to int in the
two printf lines. Are array/pointer indexes int according to the ANSI
standard?

Any way to access arrays with long indexes? e.g. string[66000]?
--

Thu, 28 Aug 1997 07:58:00 GMT

Mike Rubenstein Phoenix Contra
#2 / 4

Long as array/pointer address

Quote:

> I'd like to do the following:
> long index = 10;;
> char *string = "This is a test string";
> printf("%c\n", string[index]);
> printf("%c\n", *(string + index));
> but when I compile the above in a 16bit compiler (haven't tried it on a
> 32bit compiler), the compiler apparently casts the index to int in the
> two printf lines. Are array/pointer indexes int according to the ANSI
> standard?

The standard allows any integral type. However, the compiler is allowed to
use magic. In many 16 bit implementations objects larger than can be
indexed with a 16 bit integer are not supported or are supported only in
some non-standard way (e.g., far in most PC compilers). If the compiler knows
that the object cannot be large enough to need a long for indexing it may
optimize by converting to int (or, for that matter, to char) when it does
the calculation.

--
Mike Rubenstein

Thu, 04 Sep 1997 09:03:22 GMT

Jim Tri
#3 / 4

Long as array/pointer address

-=> Quoting Rui M. Pereira to All <=-

RMP> but when I compile the above in a 16bit compiler (haven't tried it on
RMP> a 32bit compiler), the compiler apparently casts the index to int in
RMP> the two printf lines. Are array/pointer indexes int according to the
RMP> ANSI standard?

RMP> Any way to access arrays with long indexes? e.g. string[66000]?

The problem is not that the index is cast to an int, the problem is that
on a 16bit machine, POINTERS ARE 16 BITS! The only ways to do it are
1) declare the pointers as far and do segment manipulation
2) declare the pointers as huge

Follow-ups to comp.os.msdos.programmers

Just a Thought,
Jim Trigg

... If it wasn't for C, we would be using BASI, PASAL and OBOL!
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Sun, 07 Sep 1997 07:59:00 GMT