namespace std {
using sig_atomic_t = see below;
// [support.signal], signal handlers
extern "C" using signal-handler = void(int); // exposition only
signal-handler* signal(int sig, signal-handler* func);
int raise(int sig);
}
#define SIG_DFL see below
#define SIG_ERR see below
#define SIG_IGN see below
#define SIGABRT see below
#define SIGFPE see below
#define SIGILL see below
#define SIGINT see below
#define SIGSEGV see below
#define SIGTERM see below