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27 ****************************************************************************/
29 /****************************************************************************
30 * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
31 * and: Eric S. Raymond <esr@snark.thyrsus.com> *
32 * and: Thomas E. Dickey 1995-on *
33 ****************************************************************************/
38 ** The routine _nc_signal_handler().
41 #include <curses.priv.h>
43 #include <SigAction.h>
45 #if SVR4_ACTION && !defined(_POSIX_SOURCE)
49 MODULE_ID("$Id: lib_tstp.c,v 1.37 2008/05/03 16:24:56 tom Exp $")
51 #if defined(SIGTSTP) && (HAVE_SIGACTION || HAVE_SIGVEC)
87 return "unknown signal";
93 * Note: This code is fragile! Its problem is that different OSs
94 * handle restart of system calls interrupted by signals differently.
95 * The ncurses code needs signal-call restart to happen -- otherwise,
96 * interrupted wgetch() calls will return FAIL, probably making the
97 * application think the input stream has ended and it should
98 * terminate. In particular, you know you have this problem if, when
99 * you suspend an ncurses-using lynx with ^Z and resume, it dies
102 * Default behavior of POSIX sigaction(2) is not to restart
103 * interrupted system calls, but Linux's sigaction does it anyway (at
104 * least, on and after the 1.1.47 I (esr) use). Thus this code works
105 * OK under Linux. The 4.4BSD sigaction(2) supports a (non-portable)
106 * SA_RESTART flag that forces the right behavior. Thus, this code
107 * should work OK under BSD/OS, NetBSD, and FreeBSD (let us know if it
110 * Stock System Vs (and anything else using a strict-POSIX
111 * sigaction(2) without SA_RESTART) may have a problem. Possible
114 * sigvec restarts by default (SV_INTERRUPT flag to not restart)
115 * signal restarts by default in SVr4 (assuming you link with -lucb)
116 * and BSD, but not SVr3.
117 * sigset restarts, but is only available under SVr4/Solaris.
119 * The signal(3) call is mandated by the ANSI standard, and its
120 * interaction with sigaction(2) is described in the POSIX standard
121 * (3.3.4.2, page 72,line 934). According to section 8.1, page 191,
122 * however, signal(3) itself is not required by POSIX.1. And POSIX is
123 * silent on whether it is required to restart signals.
125 * So. The present situation is, we use sigaction(2) with no
126 * guarantee of restart anywhere but on Linux and BSD. We could
127 * switch to signal(3) and collar Linux, BSD, and SVr4. Any way
128 * we slice it, System V UNIXes older than SVr4 will probably lose
129 * (this may include XENIX).
131 * This implementation will probably be changed to use signal(3) in
132 * the future. If nothing else, it's simpler...
137 tstp(int dummy GCC_UNUSED)
139 sigset_t mask, omask;
140 sigaction_t act, oact;
146 T(("tstp() called"));
149 * The user may have changed the prog_mode tty bits, so save them.
151 * But first try to detect whether we still are in the foreground
152 * process group - if not, an interactive shell may already have
153 * taken ownership of the tty and modified the settings when our
154 * parent was stopped before us, and we would likely pick up the
155 * settings already modified by the shell.
157 if (SP != 0 && !SP->_endwin) /* don't do this if we're not in curses */
159 if (tcgetpgrp(STDIN_FILENO) == getpgrp())
164 * Block window change and timer signals. The latter
165 * is because applications use timers to decide when
166 * to repaint the screen.
168 (void) sigemptyset(&mask);
169 (void) sigaddset(&mask, SIGALRM);
171 (void) sigaddset(&mask, SIGWINCH);
173 (void) sigprocmask(SIG_BLOCK, &mask, &omask);
176 sigttou_blocked = sigismember(&omask, SIGTTOU);
177 if (!sigttou_blocked) {
178 (void) sigemptyset(&mask);
179 (void) sigaddset(&mask, SIGTTOU);
180 (void) sigprocmask(SIG_BLOCK, &mask, NULL);
185 * End window mode, which also resets the terminal state to the
186 * original (pre-curses) modes.
190 /* Unblock SIGTSTP. */
191 (void) sigemptyset(&mask);
192 (void) sigaddset(&mask, SIGTSTP);
194 if (!sigttou_blocked) {
195 /* Unblock this too if it wasn't blocked on entry */
196 (void) sigaddset(&mask, SIGTTOU);
199 (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
201 /* Now we want to resend SIGSTP to this process and suspend it */
202 act.sa_handler = SIG_DFL;
203 sigemptyset(&act.sa_mask);
206 act.sa_flags |= SA_RESTART;
207 #endif /* SA_RESTART */
208 sigaction(SIGTSTP, &act, &oact);
209 kill(getpid(), SIGTSTP);
211 /* Process gets suspended...time passes...process resumes */
213 T(("SIGCONT received"));
214 sigaction(SIGTSTP, &oact, NULL);
218 * If the user modified the tty state while suspended, he wants
219 * those changes to stick. So save the new "default" terminal state.
224 * This relies on the fact that doupdate() will restore the
225 * program-mode tty state, and issue enter_ca_mode if need be.
229 /* Reset the signals. */
230 (void) sigprocmask(SIG_SETMASK, &omask, NULL);
232 #endif /* USE_SIGTSTP */
238 * Actually, doing any sort of I/O from within an signal handler is
239 * "unsafe". But we'll _try_ to clean up the screen and terminal
240 * settings on the way out.
242 if (!_nc_globals.cleanup_nested++
244 || sig == SIGQUIT)) {
245 #if HAVE_SIGACTION || HAVE_SIGVEC
247 sigemptyset(&act.sa_mask);
249 act.sa_handler = SIG_IGN;
250 if (sigaction(sig, &act, NULL) == 0)
252 if (signal(sig, SIG_IGN) != SIG_ERR)
256 for (each_screen(scan)) {
258 && isatty(fileno(scan->_ofp))) {
259 scan->_cleanup = TRUE;
260 scan->_outch = _nc_outch;
265 SP->_endwin = FALSE; /* in case we have an atexit! */
274 sigwinch(int sig GCC_UNUSED)
276 _nc_globals.have_sigwinch = 1;
278 #endif /* USE_SIGWINCH */
281 * If the given signal is still in its default state, set it to the given
285 CatchIfDefault(int sig, RETSIGTYPE (*handler) (int))
288 #if HAVE_SIGACTION || HAVE_SIGVEC
292 memset(&new_act, 0, sizeof(new_act));
293 sigemptyset(&new_act.sa_mask);
298 new_act.sa_flags |= SA_RESTART;
299 #endif /* SA_RESTART */
300 new_act.sa_handler = handler;
302 if (sigaction(sig, NULL, &old_act) == 0
303 && (old_act.sa_handler == SIG_DFL
304 || old_act.sa_handler == handler
306 || (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
309 (void) sigaction(sig, &new_act, NULL);
314 #else /* !HAVE_SIGACTION */
315 RETSIGTYPE (*ohandler) (int);
317 ohandler = signal(sig, SIG_IGN);
318 if (ohandler == SIG_DFL
319 || ohandler == handler
321 || (sig == SIGWINCH && ohandler == SIG_IGN)
324 signal(sig, handler);
327 signal(sig, ohandler);
331 T(("CatchIfDefault - will %scatch %s",
332 result ? "" : "not ", signal_name(sig)));
337 * This is invoked once at the beginning (e.g., from 'initscr()'), to
338 * initialize the signal catchers, and thereafter when spawning a shell (and
339 * returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
341 * If the application has already set one of the signals, we'll not modify it
342 * (during initialization).
344 * The XSI document implies that we shouldn't keep the SIGTSTP handler if
345 * the caller later changes its mind, but that doesn't seem correct.
348 _nc_signal_handler(bool enable)
350 T((T_CALLED("_nc_signal_handler(%d)"), enable));
351 #if USE_SIGTSTP /* Xenix 2.x doesn't have SIGTSTP, for example */
353 static bool ignore_tstp = FALSE;
356 static sigaction_t new_sigaction, old_sigaction;
359 new_sigaction.sa_handler = SIG_IGN;
360 sigaction(SIGTSTP, &new_sigaction, &old_sigaction);
361 } else if (new_sigaction.sa_handler != SIG_DFL) {
362 sigaction(SIGTSTP, &old_sigaction, NULL);
363 } else if (sigaction(SIGTSTP, NULL, &old_sigaction) == 0
364 && (old_sigaction.sa_handler == SIG_DFL)) {
365 sigemptyset(&new_sigaction.sa_mask);
367 new_sigaction.sa_flags |= SA_RESTART;
368 #endif /* SA_RESTART */
369 new_sigaction.sa_handler = tstp;
370 (void) sigaction(SIGTSTP, &new_sigaction, NULL);
376 #endif /* !USE_SIGTSTP */
378 if (!_nc_globals.init_signals) {
380 CatchIfDefault(SIGINT, cleanup);
381 CatchIfDefault(SIGTERM, cleanup);
383 CatchIfDefault(SIGWINCH, sigwinch);
385 _nc_globals.init_signals = TRUE;