Presently, no. There are operations, such as with semaphores, where this sort
of functionality might be used but has been left unspecified as many CPUs don't
support exchanges; for most older ones only loads and stores are atomic, and
the volatile modifier and sigatomic_t types are geared to be used this way.
Without direct hardware support, on those systems some aspects of c11s
stdatomic interfaces get a performance and code size penalty to emulate
robustly; possibly why it's an optional header entirely.
On Friday, February 14, 2020 Danny Niu wrote:
As asked, is there an CMPXGCHG-like function in the standard?
I tried looking for keywords such as cmp, comp, ch, but
nothing turned up in the system interfaces list.
The C language introduced atomic functions in C11 though.
