pqsignal.c

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/*-------------------------------------------------------------------------
 *
 * pqsignal.c
 *    reliable BSD-style signal(2) routine stolen from RWW who stole it
 *    from Stevens...
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/port/pqsignal.c
 *
 *  We now assume that all Unix-oid systems have POSIX sigaction(2)
 *  with support for restartable signals (SA_RESTART).  We used to also
 *  support BSD-style signal(2), but there really shouldn't be anything
 *  out there anymore that doesn't have the POSIX API.
 *
 *  Windows, of course, is resolutely in a class by itself.  In the backend,
 *  we don't use this file at all; src/backend/port/win32/signal.c provides
 *  pqsignal() for the backend environment.  Frontend programs can use
 *  this version of pqsignal() if they wish, but beware that this does
 *  not provide restartable signals on Windows.
 *
 * ------------------------------------------------------------------------
 */
 
#include "c.h"
 
#include <signal.h>
 
#ifndef FRONTEND
#include "libpq/pqsignal.h"
#endif
 
/*
 * Set up a signal handler, with SA_RESTART, for signal "signo"
 *
 * Returns the previous handler.
 */
pqsigfunc
pqsignal(int signo, pqsigfunc func)
{
#if !(defined(WIN32) && defined(FRONTEND))
    struct sigaction act,
                oact;
 
    act.sa_handler = func;
    sigemptyset(&act.sa_mask);
    act.sa_flags = SA_RESTART;
#ifdef SA_NOCLDSTOP
    if (signo == SIGCHLD)
        act.sa_flags |= SA_NOCLDSTOP;
#endif
    if (sigaction(signo, &act, &oact) < 0)
        return SIG_ERR;
    return oact.sa_handler;
#else
    /* Forward to Windows native signal system. */
    return signal(signo, func);
#endif
}