Re: Division in loop

[Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx>]

Randi Botse wrote:

> Thanks Glynn for let me know that the void* pointer arithmetic is
> undefined, and gcc automatically cast it to char* pointer... is this
> because void* doesn't have a size?

Technically, it's because the standard says that it's undefined.

Pointer arithmetic is defined in terms of pointers to array elements,
e.g. if you have:

	int foo[N];
	int *p = &foo[A];
	int *q = p+B;
	int *r = &foo[A+B];

then r==q. But you can't have an array of "void", so pointer
arithmetic on void* isn't meaningful.

> im curious when i do sizeof(void*),
> my machine tell me sizeof(void*) is 4kb... i thnk when i do (void* +
> 1) that's means "4 kb after void*"?....

The result of sizeof is in bytes (technically, "char"s; sizeof(char)
is guaranteed to be 1).

The result of "sizeof" applied to any pointer type will typically be 4
bytes on 32-bit systems or 8 bytes on 64-bit systems. Although it's
possible for pointers to different types to have different sizes, it's
rare.

> i run the code in GNOME terminal, that's means stdout connected to xterm?

No, to Gnome terminal; xterm is similar.

It's possible that the behaviour which you experience is a property of
the terminal emulator. You might try running the program on a
different terminal emulator, or on a VT, to see if the same problem
occurs there.

-- 
Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx>
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