Benjamin Grange writes:
> Hi,
> the following code converts a class A which is know to be of the size
> of an int into a void*. This allow to save it in a list of void*.
> When compiled without -O3 (or 2) it works. But with -O3 or 2, on
> x86_64, the line intarray[1] = 0 is removed in the assembly output and
> it doesn't work anymore.
> Changing function topointer() into this:
> return (void *) (unsigned long)(*(((unsigned int *)&a)));
> fix the problem.
>
> So, is it a bug in gcc or does this does something bad?
> Also do you know a good way to convert an int to a pointer?
>
> Thank you.
> Ben
>
> /*----- code follows ------*/
> #include <stdio.h>
>
> void **listA;
>
> class A {
> public:
> A(int n) { x = n; }
> int x;
> };
>
> void *topointer(A a)
> {
> unsigned int intarray[2];
> intarray[0] = *(((unsigned int *)&a));
This is a bug in your code. If you really need to break the type
system by accessing an object by something other than its real type,
use a union:
union
{
A A_kludge;
unsigned int uint_kludge[2];
void *nonsense;
} kludge;
kludge.A = a;
...
Andrew.
