/*-------------------------------------------------------------------------
 *
 * pqsignal.c--
 *    reliable BSD-style signal(2) routine stolen from RWW who stole it
 *    from Stevens...
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/libpq/pqsignal.c,v 1.4 1996/11/18 02:25:09 bryanh Exp $
 *
 * NOTES
 *	This shouldn't be in libpq, but the monitor and some other
 *	things need it...
 *
 *  A NOTE ABOUT SIGNAL HANDLING ACROSS THE VARIOUS PLATFORMS.
 *
 *  config.h defines the macro USE_POSIX_SIGNALS for some platforms and
 *  not for others.  This file and pqsignal.h use that macro to decide
 *  how to handle signalling.
 *
 *  signal(2) handling - this is here because it affects some of 
 *  the frontend commands as well as the backend server.
 * 
 *  Ultrix and SunOS provide BSD signal(2) semantics by default.
 * 
 *  SVID2 and POSIX signal(2) semantics differ from BSD signal(2) 
 *  semantics.  We can use the POSIX sigaction(2) on systems that
 *  allow us to request restartable signals (SA_RESTART).
 * 
 *  Some systems don't allow restartable signals at all unless we 
 *  link to a special BSD library.
 * 
 *  We devoutly hope that there aren't any systems that provide
 *  neither POSIX signals nor BSD signals.  The alternative 
 *  is to do signal-handler reinstallation, which doesn't work well 
 *  at all.
 * ------------------------------------------------------------------------*/
#include <postgres.h>

#include <libpq/pqsignal.h>

pqsigfunc
pqsignal(int signo, pqsigfunc func)
{
#if defined(USE_POSIX_SIGNALS)
    struct sigaction act, oact;
    
    act.sa_handler = func;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    if (signo != SIGALRM) {
	act.sa_flags |= SA_RESTART;
    }
    if (sigaction(signo, &act, &oact) < 0)
	return(SIG_ERR);
    return(oact.sa_handler);
#else /* !USE_POSIX_SIGNALS */
    Assert(0);
    return 0;
#endif /* !USE_POSIX_SIGNALS */
}
