Hello,

Let's have a declaration:
struct sigaction sa;

For the partial expression of "sa." only sa_mask and sa_flags are proposed. No proposals for the union which contains sa_handler and sa_sigaction.
And if I enter manually "sa.sa_sigaction = NULL;" - "sa_sigaction" expression part is underlined with red.

The code is compilable anyway:
-------------------------------
#include <cstdlib>
#include <signal.h>

int
main(int argc, char** argv) {
    struct sigaction sa;
    sa.sa_sigaction = NULL;
    std::exit(0);
}
-------------------------------