GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libcurses/tty/lib_tstp.c Lines: 0 85 0.0 %
Date: 2017-11-13 Branches: 0 50 0.0 %

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/* $OpenBSD: lib_tstp.c,v 1.11 2011/05/30 21:59:35 deraadt Exp $ */
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/****************************************************************************
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 * Copyright (c) 1998-2007,2008 Free Software Foundation, Inc.              *
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 *                                                                          *
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 * Permission is hereby granted, free of charge, to any person obtaining a  *
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 * copy of this software and associated documentation files (the            *
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 * "Software"), to deal in the Software without restriction, including      *
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 * without limitation the rights to use, copy, modify, merge, publish,      *
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 * distribute, distribute with modifications, sublicense, and/or sell       *
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 * copies of the Software, and to permit persons to whom the Software is    *
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 * furnished to do so, subject to the following conditions:                 *
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 *                                                                          *
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 * The above copyright notice and this permission notice shall be included  *
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 * in all copies or substantial portions of the Software.                   *
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 *                                                                          *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
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 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
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 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
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 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
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 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
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 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
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 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
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 *                                                                          *
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 * Except as contained in this notice, the name(s) of the above copyright   *
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 * holders shall not be used in advertising or otherwise to promote the     *
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 * sale, use or other dealings in this Software without prior written       *
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 * authorization.                                                           *
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 ****************************************************************************/
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/****************************************************************************
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 *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
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 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
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 *     and: Thomas E. Dickey                        1995-on                 *
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 ****************************************************************************/
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/*
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**	lib_tstp.c
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**
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**	The routine _nc_signal_handler().
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**
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*/
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#include <curses.priv.h>
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#include <SigAction.h>
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#if SVR4_ACTION && !defined(_POSIX_SOURCE)
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#define _POSIX_SOURCE
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#endif
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MODULE_ID("$Id: lib_tstp.c,v 1.11 2011/05/30 21:59:35 deraadt Exp $")
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#if defined(SIGTSTP) && (HAVE_SIGACTION || HAVE_SIGVEC)
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#define USE_SIGTSTP 1
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#else
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#define USE_SIGTSTP 0
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#endif
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#ifdef TRACE
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static const char *
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signal_name(int sig)
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{
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    switch (sig) {
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    case SIGALRM:
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	return "SIGALRM";
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#ifdef SIGCONT
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    case SIGCONT:
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	return "SIGCONT";
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#endif
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    case SIGINT:
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	return "SIGINT";
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    case SIGQUIT:
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	return "SIGQUIT";
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    case SIGTERM:
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	return "SIGTERM";
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#ifdef SIGTSTP
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    case SIGTSTP:
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	return "SIGTSTP";
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#endif
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#ifdef SIGTTOU
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    case SIGTTOU:
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	return "SIGTTOU";
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#endif
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#ifdef SIGWINCH
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    case SIGWINCH:
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	return "SIGWINCH";
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#endif
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    default:
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	return "unknown signal";
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    }
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}
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#endif
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/*
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 * Note: This code is fragile!  Its problem is that different OSs
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 * handle restart of system calls interrupted by signals differently.
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 * The ncurses code needs signal-call restart to happen -- otherwise,
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 * interrupted wgetch() calls will return FAIL, probably making the
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 * application think the input stream has ended and it should
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 * terminate.  In particular, you know you have this problem if, when
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 * you suspend an ncurses-using lynx with ^Z and resume, it dies
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 * immediately.
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 *
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 * Default behavior of POSIX sigaction(2) is not to restart
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 * interrupted system calls, but Linux's sigaction does it anyway (at
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 * least, on and after the 1.1.47 I (esr) use).  Thus this code works
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 * OK under Linux.  The 4.4BSD sigaction(2) supports a (non-portable)
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 * SA_RESTART flag that forces the right behavior.  Thus, this code
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 * should work OK under BSD/OS, NetBSD, and FreeBSD (let us know if it
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 * does not).
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 *
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 * Stock System Vs (and anything else using a strict-POSIX
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 * sigaction(2) without SA_RESTART) may have a problem.  Possible
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 * solutions:
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 *
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 *    sigvec      restarts by default (SV_INTERRUPT flag to not restart)
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 *    signal      restarts by default in SVr4 (assuming you link with -lucb)
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 *                and BSD, but not SVr3.
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 *    sigset      restarts, but is only available under SVr4/Solaris.
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 *
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 * The signal(3) call is mandated by the ANSI standard, and its
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 * interaction with sigaction(2) is described in the POSIX standard
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 * (3.3.4.2, page 72,line 934).  According to section 8.1, page 191,
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 * however, signal(3) itself is not required by POSIX.1.  And POSIX is
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 * silent on whether it is required to restart signals.
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 *
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 * So.  The present situation is, we use sigaction(2) with no
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 * guarantee of restart anywhere but on Linux and BSD.  We could
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 * switch to signal(3) and collar Linux, BSD, and SVr4.  Any way
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 * we slice it, System V UNIXes older than SVr4 will probably lose
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 * (this may include XENIX).
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 *
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 * This implementation will probably be changed to use signal(3) in
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 * the future.  If nothing else, it's simpler...
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 */
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#if USE_SIGTSTP
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static void
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tstp(int dummy GCC_UNUSED)
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{
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    sigset_t mask, omask;
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    sigaction_t act, oact;
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#ifdef SIGTTOU
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    int sigttou_blocked;
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#endif
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    T(("tstp() called"));
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    /*
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     * The user may have changed the prog_mode tty bits, so save them.
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     *
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     * But first try to detect whether we still are in the foreground
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     * process group - if not, an interactive shell may already have
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     * taken ownership of the tty and modified the settings when our
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     * parent was stopped before us, and we would likely pick up the
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     * settings already modified by the shell.
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     */
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    if (SP != 0 && !SP->_endwin)	/* don't do this if we're not in curses */
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#if HAVE_TCGETPGRP
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	if (tcgetpgrp(STDIN_FILENO) == getpgrp())
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#endif
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	    def_prog_mode();
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    /*
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     * Block window change and timer signals.  The latter
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     * is because applications use timers to decide when
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     * to repaint the screen.
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     */
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    (void) sigemptyset(&mask);
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    (void) sigaddset(&mask, SIGALRM);
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#if USE_SIGWINCH
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    (void) sigaddset(&mask, SIGWINCH);
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#endif
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    (void) sigprocmask(SIG_BLOCK, &mask, &omask);
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#ifdef SIGTTOU
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    sigttou_blocked = sigismember(&omask, SIGTTOU);
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    if (!sigttou_blocked) {
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	(void) sigemptyset(&mask);
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	(void) sigaddset(&mask, SIGTTOU);
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	(void) sigprocmask(SIG_BLOCK, &mask, NULL);
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    }
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#endif
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    /*
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     * End window mode, which also resets the terminal state to the
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     * original (pre-curses) modes.
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     */
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    endwin();
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    /* Unblock SIGTSTP. */
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    (void) sigemptyset(&mask);
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    (void) sigaddset(&mask, SIGTSTP);
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#ifdef SIGTTOU
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    if (!sigttou_blocked) {
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	/* Unblock this too if it wasn't blocked on entry */
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	(void) sigaddset(&mask, SIGTTOU);
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    }
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#endif
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    (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
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    /* Now we want to resend SIGSTP to this process and suspend it */
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    act.sa_handler = SIG_DFL;
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    sigemptyset(&act.sa_mask);
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    act.sa_flags = 0;
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#ifdef SA_RESTART
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    act.sa_flags |= SA_RESTART;
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#endif /* SA_RESTART */
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    sigaction(SIGTSTP, &act, &oact);
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    kill(getpid(), SIGTSTP);
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    /* Process gets suspended...time passes...process resumes */
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    T(("SIGCONT received"));
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    sigaction(SIGTSTP, &oact, NULL);
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    flushinp();
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    /*
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     * If the user modified the tty state while suspended, he wants
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     * those changes to stick.  So save the new "default" terminal state.
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     */
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    def_shell_mode();
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    /*
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     * This relies on the fact that doupdate() will restore the
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     * program-mode tty state, and issue enter_ca_mode if need be.
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     */
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    doupdate();
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    /* Reset the signals. */
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    (void) sigprocmask(SIG_SETMASK, &omask, NULL);
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}
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#endif /* USE_SIGTSTP */
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static void
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cleanup(int sig)
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{
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    /*
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     * XXX signal race.
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     *
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     * 1) Walking the SCREEN list is unsafe, since all list management
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     *    is done without any signal blocking.
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     * 2) On systems which have REENTRANT turned on, set_term() uses
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     *    _nc_lock_global() which could deadlock or misbehave in other ways.
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     * 3) endwin() calls all sorts of stuff, many of which use stdio or
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     *    other library functions which are clearly unsafe.
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     * 4) The comment about atexit() is wrong.  atexit() should never be
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     *    called, because ...
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     * 5) The call to exit() at the bottom is unsafe:  exit() depends
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     *    depends on stdio being coherent (obviously it is not).  stdio
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     *    could call free(), and also calls atexit() and dtor handlers,
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     *    which are probably not written to be safe.  The signal handler
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     *    should be calling _exit().
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     */
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    if (!_nc_globals.cleanup_nested++
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	&& (sig == SIGINT
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	    || sig == SIGQUIT)) {
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#if HAVE_SIGACTION || HAVE_SIGVEC
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	sigaction_t act;
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	sigemptyset(&act.sa_mask);
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	act.sa_flags = 0;
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	act.sa_handler = SIG_IGN;
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	if (sigaction(sig, &act, NULL) == 0)
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#else
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	if (signal(sig, SIG_IGN) != SIG_ERR)
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#endif
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	{
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	    SCREEN *scan;
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	    for (each_screen(scan)) {
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		if (scan->_ofp != 0
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		    && isatty(fileno(scan->_ofp))) {
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		    scan->_cleanup = TRUE;
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		    scan->_outch = _nc_outch;
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		}
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		set_term(scan);
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		endwin();
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		if (SP)
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		    SP->_endwin = FALSE;	/* in case we have an atexit! */
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	    }
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	}
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    }
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    exit(EXIT_FAILURE);
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}
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#if USE_SIGWINCH
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static void
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sigwinch(int sig GCC_UNUSED)
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{
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    _nc_globals.have_sigwinch = 1;
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}
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#endif /* USE_SIGWINCH */
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/*
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 * If the given signal is still in its default state, set it to the given
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 * handler.
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 */
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static int
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CatchIfDefault(int sig, RETSIGTYPE (*handler) (int))
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{
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    int result;
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#if HAVE_SIGACTION || HAVE_SIGVEC
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    sigaction_t old_act;
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    sigaction_t new_act;
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    memset(&new_act, 0, sizeof(new_act));
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    sigemptyset(&new_act.sa_mask);
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#ifdef SA_RESTART
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#ifdef SIGWINCH
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    if (sig != SIGWINCH)
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#endif
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	new_act.sa_flags |= SA_RESTART;
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#endif /* SA_RESTART */
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    new_act.sa_handler = handler;
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    if (sigaction(sig, NULL, &old_act) == 0
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	&& (old_act.sa_handler == SIG_DFL
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	    || old_act.sa_handler == handler
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#if USE_SIGWINCH
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	    || (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
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#endif
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	)) {
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	(void) sigaction(sig, &new_act, NULL);
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	result = TRUE;
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    } else {
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	result = FALSE;
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    }
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#else /* !HAVE_SIGACTION */
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    RETSIGTYPE (*ohandler) (int);
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    ohandler = signal(sig, SIG_IGN);
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    if (ohandler == SIG_DFL
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	|| ohandler == handler
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#if USE_SIGWINCH
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	|| (sig == SIGWINCH && ohandler == SIG_IGN)
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#endif
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	) {
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	signal(sig, handler);
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	result = TRUE;
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    } else {
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	signal(sig, ohandler);
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	result = FALSE;
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    }
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#endif
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    T(("CatchIfDefault - will %scatch %s",
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       result ? "" : "not ", signal_name(sig)));
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    return result;
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}
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/*
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 * This is invoked once at the beginning (e.g., from 'initscr()'), to
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 * initialize the signal catchers, and thereafter when spawning a shell (and
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 * returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
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 *
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 * If the application has already set one of the signals, we'll not modify it
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 * (during initialization).
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 *
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 * The XSI document implies that we shouldn't keep the SIGTSTP handler if
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 * the caller later changes its mind, but that doesn't seem correct.
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 */
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NCURSES_EXPORT(void)
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_nc_signal_handler(bool enable)
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{
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    T((T_CALLED("_nc_signal_handler(%d)"), enable));
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#if USE_SIGTSTP			/* Xenix 2.x doesn't have SIGTSTP, for example */
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    {
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	static bool ignore_tstp = FALSE;
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	if (!ignore_tstp) {
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	    static sigaction_t new_sigaction, old_sigaction;
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	    if (!enable) {
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		new_sigaction.sa_handler = SIG_IGN;
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		sigaction(SIGTSTP, &new_sigaction, &old_sigaction);
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	    } else if (new_sigaction.sa_handler != SIG_DFL) {
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		sigaction(SIGTSTP, &old_sigaction, NULL);
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	    } else if (sigaction(SIGTSTP, NULL, &old_sigaction) == 0
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		       && (old_sigaction.sa_handler == SIG_DFL)) {
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		sigemptyset(&new_sigaction.sa_mask);
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#ifdef SA_RESTART
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		new_sigaction.sa_flags |= SA_RESTART;
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#endif /* SA_RESTART */
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		new_sigaction.sa_handler = tstp;
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		(void) sigaction(SIGTSTP, &new_sigaction, NULL);
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	    } else {
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		ignore_tstp = TRUE;
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	    }
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	}
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    }
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#endif /* !USE_SIGTSTP */
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    if (!_nc_globals.init_signals) {
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	if (enable) {
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	    CatchIfDefault(SIGINT, cleanup);
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	    CatchIfDefault(SIGTERM, cleanup);
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#if USE_SIGWINCH
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	    CatchIfDefault(SIGWINCH, sigwinch);
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#endif
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	    _nc_globals.init_signals = TRUE;
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	}
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    }
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    returnVoid;
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}