legacy-pqsignal.c

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/*-------------------------------------------------------------------------
 *
 * legacy-pqsignal.c
 *    reliable BSD-style signal(2) routine stolen from RWW who stole it
 *    from Stevens...
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/interfaces/libpq/legacy-pqsignal.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"
 
#include <signal.h>
 
 
/*
 * This version of pqsignal() exists only because pre-9.3 releases
 * of libpq exported pqsignal(), and some old client programs still
 * depend on that.  (Since 9.3, clients are supposed to get it from
 * libpgport instead.)
 *
 * Because it is only intended for backwards compatibility, we freeze it
 * with the semantics it had in 9.2; in particular, this has different
 * behavior for SIGALRM than the version in src/port/pqsignal.c.
 *
 * libpq itself does not use this, nor does anything else in our code.
 *
 * src/include/port.h #define's pqsignal as pqsignal_fe or pqsignal_be,
 * but here we want to export just plain "pqsignal".  We can't rely on
 * port.h's extern declaration either.  (The point of those #define's
 * is to ensure that no in-tree code accidentally calls this version.)
 */
#undef pqsignal
extern pqsigfunc pqsignal(int signo, pqsigfunc func);
 
pqsigfunc
pqsignal(int signo, pqsigfunc func)
{
#ifndef WIN32
    struct sigaction act,
                oact;
 
    act.sa_handler = func;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    if (signo != SIGALRM)
        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                           /* WIN32 */
    return signal(signo, func);
#endif
}