int signal_view_usr1(void (*handler)(int)) {
    sigset_t set;
    struct sigaction sa;

    ec_meno1( sigemptyset(&set) );
    ec_meno1( sigaddset(&set, SIGUSR1) );
    ec_nzero( pthread_sigmask(SIG_UNBLOCK, &set, NULL) );

    if (handler != NULL) {
        memset(&sa, 0, sizeof(sa));
        sa.sa_handler = (*handler);
        ec_meno1( sigaction(SIGUSR1, &sa, NULL) );
    }

    return 0;

EC_CLEANUP_BGN
    return -1;
EC_CLEANUP_END
}