Vincent Torri <vincent.torri at gmail.com> wrote:
> with a code similar to that one:
>
> int i = 2;
> int j = 2;
> void *a = &i;
> void *b = &j;
> unsigned long delta = a - b;
>
> the compiler is displaying the warning "pointer to void or function used in
> arithmetic". Why is it doing so whe computing an offset ? I know that adding
> or substracting an offset to a void pointer is illegal, but when calculating
> an offset, using typed or void pointers is exactly the same.
A "void" is an "object" of unknown/unspecified size.
Pointer arithmetics for:
delta = a - b;
- means a and b need to be objects of the same type
- the differentce between the numerical values in a and
b is computed
- the result is divided by sizeof (a)
Did you ever try to use sizeof (void) in your code?
How do you like to divide by an unknown number?
A correct C-compiler does not print a warning but an error message and
aborts compilation. What the sun compiler currently does is a courtesy
to GCC users as GCC treats sizeof (void) == 1 which is in conflict with
the C-standard. If the Sun compiler would work correctly and abort here,
a lot of (broken) OSS software could not be compiled.
J?rg
--
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