Unfortunately swap context requires saving and restoring the signal mask, which, at least on Linux, requires a syscall so it is going to be at least a hundred times slower than an hand rolled implementation.
Also, although not likely to be removed anytime soon from existing systems, POSIX has declared the context API obsolescent a while ago (it might actually no longer be part of the standard).
Also, although not likely to be removed anytime soon from existing systems, POSIX has declared the context API obsolescent a while ago (it might actually no longer be part of the standard).