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+/****************************************************************************
+ * Copyright (c) 1998-2007,2008 Free Software Foundation, Inc. *
+ * *
+ * Permission is hereby granted, free of charge, to any person obtaining a *
+ * copy of this software and associated documentation files (the *
+ * "Software"), to deal in the Software without restriction, including *
+ * without limitation the rights to use, copy, modify, merge, publish, *
+ * distribute, distribute with modifications, sublicense, and/or sell *
+ * copies of the Software, and to permit persons to whom the Software is *
+ * furnished to do so, subject to the following conditions: *
+ * *
+ * The above copyright notice and this permission notice shall be included *
+ * in all copies or substantial portions of the Software. *
+ * *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
+ * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
+ * THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
+ * *
+ * Except as contained in this notice, the name(s) of the above copyright *
+ * holders shall not be used in advertising or otherwise to promote the *
+ * sale, use or other dealings in this Software without prior written *
+ * authorization. *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
+ * and: Eric S. Raymond <esr@snark.thyrsus.com> *
+ * and: Thomas E. Dickey 1995-on *
+ ****************************************************************************/
+
+/*
+** lib_tstp.c
+**
+** The routine _nc_signal_handler().
+**
+*/
+#include <curses.priv.h>
+
+#include <SigAction.h>
+
+#if SVR4_ACTION && !defined(_POSIX_SOURCE)
+#define _POSIX_SOURCE
+#endif
+
+MODULE_ID("$Id: lib_tstp.c,v 1.37 2008/05/03 16:24:56 tom Exp $")
+
+#if defined(SIGTSTP) && (HAVE_SIGACTION || HAVE_SIGVEC)
+#define USE_SIGTSTP 1
+#else
+#define USE_SIGTSTP 0
+#endif
+
+#ifdef TRACE
+static const char *
+signal_name(int sig)
+{
+ switch (sig) {
+ case SIGALRM:
+ return "SIGALRM";
+#ifdef SIGCONT
+ case SIGCONT:
+ return "SIGCONT";
+#endif
+ case SIGINT:
+ return "SIGINT";
+ case SIGQUIT:
+ return "SIGQUIT";
+ case SIGTERM:
+ return "SIGTERM";
+#ifdef SIGTSTP
+ case SIGTSTP:
+ return "SIGTSTP";
+#endif
+#ifdef SIGTTOU
+ case SIGTTOU:
+ return "SIGTTOU";
+#endif
+#ifdef SIGWINCH
+ case SIGWINCH:
+ return "SIGWINCH";
+#endif
+ default:
+ return "unknown signal";
+ }
+}
+#endif
+
+/*
+ * Note: This code is fragile! Its problem is that different OSs
+ * handle restart of system calls interrupted by signals differently.
+ * The ncurses code needs signal-call restart to happen -- otherwise,
+ * interrupted wgetch() calls will return FAIL, probably making the
+ * application think the input stream has ended and it should
+ * terminate. In particular, you know you have this problem if, when
+ * you suspend an ncurses-using lynx with ^Z and resume, it dies
+ * immediately.
+ *
+ * Default behavior of POSIX sigaction(2) is not to restart
+ * interrupted system calls, but Linux's sigaction does it anyway (at
+ * least, on and after the 1.1.47 I (esr) use). Thus this code works
+ * OK under Linux. The 4.4BSD sigaction(2) supports a (non-portable)
+ * SA_RESTART flag that forces the right behavior. Thus, this code
+ * should work OK under BSD/OS, NetBSD, and FreeBSD (let us know if it
+ * does not).
+ *
+ * Stock System Vs (and anything else using a strict-POSIX
+ * sigaction(2) without SA_RESTART) may have a problem. Possible
+ * solutions:
+ *
+ * sigvec restarts by default (SV_INTERRUPT flag to not restart)
+ * signal restarts by default in SVr4 (assuming you link with -lucb)
+ * and BSD, but not SVr3.
+ * sigset restarts, but is only available under SVr4/Solaris.
+ *
+ * The signal(3) call is mandated by the ANSI standard, and its
+ * interaction with sigaction(2) is described in the POSIX standard
+ * (3.3.4.2, page 72,line 934). According to section 8.1, page 191,
+ * however, signal(3) itself is not required by POSIX.1. And POSIX is
+ * silent on whether it is required to restart signals.
+ *
+ * So. The present situation is, we use sigaction(2) with no
+ * guarantee of restart anywhere but on Linux and BSD. We could
+ * switch to signal(3) and collar Linux, BSD, and SVr4. Any way
+ * we slice it, System V UNIXes older than SVr4 will probably lose
+ * (this may include XENIX).
+ *
+ * This implementation will probably be changed to use signal(3) in
+ * the future. If nothing else, it's simpler...
+ */
+
+#if USE_SIGTSTP
+static void
+tstp(int dummy GCC_UNUSED)
+{
+ sigset_t mask, omask;
+ sigaction_t act, oact;
+
+#ifdef SIGTTOU
+ int sigttou_blocked;
+#endif
+
+ T(("tstp() called"));
+
+ /*
+ * The user may have changed the prog_mode tty bits, so save them.
+ *
+ * But first try to detect whether we still are in the foreground
+ * process group - if not, an interactive shell may already have
+ * taken ownership of the tty and modified the settings when our
+ * parent was stopped before us, and we would likely pick up the
+ * settings already modified by the shell.
+ */
+ if (SP != 0 && !SP->_endwin) /* don't do this if we're not in curses */
+#if HAVE_TCGETPGRP
+ if (tcgetpgrp(STDIN_FILENO) == getpgrp())
+#endif
+ def_prog_mode();
+
+ /*
+ * Block window change and timer signals. The latter
+ * is because applications use timers to decide when
+ * to repaint the screen.
+ */
+ (void) sigemptyset(&mask);
+ (void) sigaddset(&mask, SIGALRM);
+#if USE_SIGWINCH
+ (void) sigaddset(&mask, SIGWINCH);
+#endif
+ (void) sigprocmask(SIG_BLOCK, &mask, &omask);
+
+#ifdef SIGTTOU
+ sigttou_blocked = sigismember(&omask, SIGTTOU);
+ if (!sigttou_blocked) {
+ (void) sigemptyset(&mask);
+ (void) sigaddset(&mask, SIGTTOU);
+ (void) sigprocmask(SIG_BLOCK, &mask, NULL);
+ }
+#endif
+
+ /*
+ * End window mode, which also resets the terminal state to the
+ * original (pre-curses) modes.
+ */
+ endwin();
+
+ /* Unblock SIGTSTP. */
+ (void) sigemptyset(&mask);
+ (void) sigaddset(&mask, SIGTSTP);
+#ifdef SIGTTOU
+ if (!sigttou_blocked) {
+ /* Unblock this too if it wasn't blocked on entry */
+ (void) sigaddset(&mask, SIGTTOU);
+ }
+#endif
+ (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
+
+ /* Now we want to resend SIGSTP to this process and suspend it */
+ act.sa_handler = SIG_DFL;
+ sigemptyset(&act.sa_mask);
+ act.sa_flags = 0;
+#ifdef SA_RESTART
+ act.sa_flags |= SA_RESTART;
+#endif /* SA_RESTART */
+ sigaction(SIGTSTP, &act, &oact);
+ kill(getpid(), SIGTSTP);
+
+ /* Process gets suspended...time passes...process resumes */
+
+ T(("SIGCONT received"));
+ sigaction(SIGTSTP, &oact, NULL);
+ flushinp();
+
+ /*
+ * If the user modified the tty state while suspended, he wants
+ * those changes to stick. So save the new "default" terminal state.
+ */
+ def_shell_mode();
+
+ /*
+ * This relies on the fact that doupdate() will restore the
+ * program-mode tty state, and issue enter_ca_mode if need be.
+ */
+ doupdate();
+
+ /* Reset the signals. */
+ (void) sigprocmask(SIG_SETMASK, &omask, NULL);
+}
+#endif /* USE_SIGTSTP */
+
+static void
+cleanup(int sig)
+{
+ /*
+ * Actually, doing any sort of I/O from within an signal handler is
+ * "unsafe". But we'll _try_ to clean up the screen and terminal
+ * settings on the way out.
+ */
+ if (!_nc_globals.cleanup_nested++
+ && (sig == SIGINT
+ || sig == SIGQUIT)) {
+#if HAVE_SIGACTION || HAVE_SIGVEC
+ sigaction_t act;
+ sigemptyset(&act.sa_mask);
+ act.sa_flags = 0;
+ act.sa_handler = SIG_IGN;
+ if (sigaction(sig, &act, NULL) == 0)
+#else
+ if (signal(sig, SIG_IGN) != SIG_ERR)
+#endif
+ {
+ SCREEN *scan;
+ for (each_screen(scan)) {
+ if (scan->_ofp != 0
+ && isatty(fileno(scan->_ofp))) {
+ scan->_cleanup = TRUE;
+ scan->_outch = _nc_outch;
+ }
+ set_term(scan);
+ endwin();
+ if (SP)
+ SP->_endwin = FALSE; /* in case we have an atexit! */
+ }
+ }
+ }
+ exit(EXIT_FAILURE);
+}
+
+#if USE_SIGWINCH
+static void
+sigwinch(int sig GCC_UNUSED)
+{
+ _nc_globals.have_sigwinch = 1;
+}
+#endif /* USE_SIGWINCH */
+
+/*
+ * If the given signal is still in its default state, set it to the given
+ * handler.
+ */
+static int
+CatchIfDefault(int sig, RETSIGTYPE (*handler) (int))
+{
+ int result;
+#if HAVE_SIGACTION || HAVE_SIGVEC
+ sigaction_t old_act;
+ sigaction_t new_act;
+
+ memset(&new_act, 0, sizeof(new_act));
+ sigemptyset(&new_act.sa_mask);
+#ifdef SA_RESTART
+#ifdef SIGWINCH
+ if (sig != SIGWINCH)
+#endif
+ new_act.sa_flags |= SA_RESTART;
+#endif /* SA_RESTART */
+ new_act.sa_handler = handler;
+
+ if (sigaction(sig, NULL, &old_act) == 0
+ && (old_act.sa_handler == SIG_DFL
+ || old_act.sa_handler == handler
+#if USE_SIGWINCH
+ || (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
+#endif
+ )) {
+ (void) sigaction(sig, &new_act, NULL);
+ result = TRUE;
+ } else {
+ result = FALSE;
+ }
+#else /* !HAVE_SIGACTION */
+ RETSIGTYPE (*ohandler) (int);
+
+ ohandler = signal(sig, SIG_IGN);
+ if (ohandler == SIG_DFL
+ || ohandler == handler
+#if USE_SIGWINCH
+ || (sig == SIGWINCH && ohandler == SIG_IGN)
+#endif
+ ) {
+ signal(sig, handler);
+ result = TRUE;
+ } else {
+ signal(sig, ohandler);
+ result = FALSE;
+ }
+#endif
+ T(("CatchIfDefault - will %scatch %s",
+ result ? "" : "not ", signal_name(sig)));
+ return result;
+}
+
+/*
+ * This is invoked once at the beginning (e.g., from 'initscr()'), to
+ * initialize the signal catchers, and thereafter when spawning a shell (and
+ * returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
+ *
+ * If the application has already set one of the signals, we'll not modify it
+ * (during initialization).
+ *
+ * The XSI document implies that we shouldn't keep the SIGTSTP handler if
+ * the caller later changes its mind, but that doesn't seem correct.
+ */
+NCURSES_EXPORT(void)
+_nc_signal_handler(bool enable)
+{
+ T((T_CALLED("_nc_signal_handler(%d)"), enable));
+#if USE_SIGTSTP /* Xenix 2.x doesn't have SIGTSTP, for example */
+ {
+ static bool ignore_tstp = FALSE;
+
+ if (!ignore_tstp) {
+ static sigaction_t new_sigaction, old_sigaction;
+
+ if (!enable) {
+ new_sigaction.sa_handler = SIG_IGN;
+ sigaction(SIGTSTP, &new_sigaction, &old_sigaction);
+ } else if (new_sigaction.sa_handler != SIG_DFL) {
+ sigaction(SIGTSTP, &old_sigaction, NULL);
+ } else if (sigaction(SIGTSTP, NULL, &old_sigaction) == 0
+ && (old_sigaction.sa_handler == SIG_DFL)) {
+ sigemptyset(&new_sigaction.sa_mask);
+#ifdef SA_RESTART
+ new_sigaction.sa_flags |= SA_RESTART;
+#endif /* SA_RESTART */
+ new_sigaction.sa_handler = tstp;
+ (void) sigaction(SIGTSTP, &new_sigaction, NULL);
+ } else {
+ ignore_tstp = TRUE;
+ }
+ }
+ }
+#endif /* !USE_SIGTSTP */
+
+ if (!_nc_globals.init_signals) {
+ if (enable) {
+ CatchIfDefault(SIGINT, cleanup);
+ CatchIfDefault(SIGTERM, cleanup);
+#if USE_SIGWINCH
+ CatchIfDefault(SIGWINCH, sigwinch);
+#endif
+ _nc_globals.init_signals = TRUE;
+ }
+ }
+ returnVoid;
+}