Suppose I have
aligned uint8_t vars[2] = {0x00, 0x00};
Thread 1:
CAS((uint16_t *)vars, 0x0000, 0x0001);
Thread 2:
store(&vars[0], 0x01);
x = load(&vars[1]);
Assume big endian. Is the outcome [CAS succeeds, x = 0] possible?
[fixed example]
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Accessing uint8_t as uint16_t is undefined. You could define it as uint16_t and access it as char though. However, there's no proper memory model / semantics for old style atomics. You need to use C++11 atomics and they don't support what you want to do in any well defined way.
You could define it as std::atomic_uint16_t but then I don't think it's well-defined to store / load into that as a char pointer. Even if it was, I don't think it fits into their memory model. There's definitely no way to mix different sizes of atomic operations for u8 and u16.
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Yeah, that’s pretty much what I thought. Any idea if I’m right that this will work on real hardware? (Assume I just use inline assembly for the loads/stores to skirt questions about UB.)
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