then how do other compilers/library implementations behave? you said that gcc doesn't follow the suggestion of the standard to avoid per-process states.
well gcc certainly follows the recommendation of the standard by making the *lock-free* atomics both address-free and free from process state, I don't read the standard as suggesting (or even requiring) anything for emulated atomics
in my reading the sentence `The implementation should not depend on any per- process state' is not restricted to lock-free atomics, but i am not a native speaker and i could be wrong.
cacheline sizes vary, but a compiler might optimize for a commonly used value. however i've been hit more than once by compilers, which are changing the size of structs.
under what circumstances did the sizes change? Currently I cannot imagine this *not* being an ABI violation
iirc a struct { int i; void*p}; had a size of 16 bytes or 12 bytes depending if it was packed or not. but also empty-base-class optimization should change the size of a class. cheers, tim