Re: OSAtomic built-in operations
Re: OSAtomic built-in operations
- Subject: Re: OSAtomic built-in operations
- From: Dave Keck <email@hidden>
- Date: Mon, 07 May 2012 01:00:14 -0400
>> union {
>> int32_t s;
>> uint32_t u;
>> } atomicvar;
>> atomicvar.u = 0;
>> OSAtomicCompareAndSwap32(0, 1, &atomicvar.s);
>> OSAtomicOr32Orig(0, &atomicvar.u);
>
> I've seen this technique in other places. Why is that better than just casting pointer types? Like this:
>
> int32_t s;
> uint32_t u;
>
> u = *(uint32_t*) &s;
Indeed -- and my understanding is C only guarantees that the most
recently-assigned member of a union to be valid. So if the OP is
worried about correctness, it would seem the union approach doesn't
help.
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