[Kde-bindings] Fwd: Qyoto/Kimono: A 64 bit unsafe function, build trouble on Debian unstable

[Richard Dale]

On Sunday 27 May 2007, Arno Rehn wrote:
>                 qint64 key = (qint64) o->ptr;
>                 return (int) ((key >> (8 * sizeof(int) - 1)) ^ key);
Well I tried a quick experiment, and I'm not sure the result has the same 
bytes as the original 'o->ptr' when there are 32 bits to a pointer and for 
ints:

#include <stdio.h>
int main(int argc, char * argv[]) {
    int before_calc = 0xAABBCCDD;
    long long key = (long long) before_calc;
    int after_calc =  (int) ((key >> (8 * sizeof(int) - 1)) ^ key);
    printf("before calc: 0x%8.8x after_calc: 0x%8.8x\n", before_calc, 
after_calc);
    printf("key: 0x%16.16x\n", key);
    return 0;
}

gives:
before calc: 0xaabbccdd after_calc: 0x55443322
key: 0x00000000aabbccdd

But there may be something wrong with the test. 

I think we should just '&' with 0xFFFFFFF to get the bottom 32 bits when 
pointers are 32 bits, and use the above calc when they are 64 bits:

    if (sizeof(void*) > sizeof(int)) {
        qint64 key = (qint64) o->ptr;
        return (int) ((key >> (8 * sizeof(int) - 1)) ^ key);
    } else {
        return (int) (o->ptr & 0xFFFFFFFF);
    }

Does this code compile on a 64 bit machine though?

-- Richard