Re: Fw: GCC interpretation of C11 atomics (DR 459)

[Ruslan Nikolaev via gcc]

> 1) your proposal would make gcc non-conforming to iso c unless it changes how 
> static const objects are emitted.
I do not think, ISO C requires to put const objects to .rodata. And it is 
easily solved by not placing it there for _Atomic objects that cannot be safely 
loaded from read-only memory.

> 2) the two implementations are not abi compatible, the choice is already 
> made, changing it is an abi break.
Since current implementations redirects to libatomic anyway, almost nothing 
should break. The only case it will break -- if somebody erroneously used 
atomic_load for 128-bit type on read-only memory (which is, again, not 
guaranteed by the standard). In practice, this case almost non-existent. The 
worst that may happen -- you will a segfault right away.

> 3) Torvald pointed out further considerations such as users expecting 
> lock-free atomic loads to be faster than stores.

Is it even true? Is it faster to use some global lock (implemented through RMW) 
than a single RMW operation? If you use this global lock, you will not get 
loads faster than stores.