c++ - Compare and exchange weak an atomic variable -

i have code (updated correct union-struct ordering):

union {     struct {          short b;          short c;     };      std::atomic<int> d; } 

and want swap both b , c (hence atomic d) value zero, using compare_exchange_weak(). have this:

a a; . . . std::atomic<int32_t> x = a.d.load(std::memory_order_relaxed); int32_t valtoreplace = 0;  return a.d.compare_exchange_weak(valtoreplace, x, std::memory_order_release, std::memory_order_relaxed); 

how do this? argument compare_exchange_weak(), x, cannot atomic- confused?

the local variable x shouldn't atomic. there's no reason be, , can't used argument compare_exchange_weak, expects regular value.

i won't comment on whatever you're trying union, since makes no sense me.