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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 MODULE_ID("$Id: lib_tstp.c,v 1.48 2014/04/26 18:47:35 juergen Exp $")
47 #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 handle_SIGTSTP(int dummy GCC_UNUSED)
139 SCREEN *sp = CURRENT_SCREEN;
140 sigset_t mask, omask;
141 sigaction_t act, oact;
147 _nc_globals.have_sigtstp = 1;
148 T(("handle_SIGTSTP() called"));
151 * The user may have changed the prog_mode tty bits, so save them.
153 * But first try to detect whether we still are in the foreground
154 * process group - if not, an interactive shell may already have
155 * taken ownership of the tty and modified the settings when our
156 * parent was stopped before us, and we would likely pick up the
157 * settings already modified by the shell.
159 if (sp != 0 && !sp->_endwin) /* don't do this if we're not in curses */
161 if (tcgetpgrp(STDIN_FILENO) == getpgrp())
163 NCURSES_SP_NAME(def_prog_mode) (NCURSES_SP_ARG);
166 * Block window change and timer signals. The latter
167 * is because applications use timers to decide when
168 * to repaint the screen.
170 (void) sigemptyset(&mask);
172 (void) sigaddset(&mask, SIGALRM);
175 (void) sigaddset(&mask, SIGWINCH);
177 (void) sigprocmask(SIG_BLOCK, &mask, &omask);
180 sigttou_blocked = sigismember(&omask, SIGTTOU);
181 if (!sigttou_blocked) {
182 (void) sigemptyset(&mask);
183 (void) sigaddset(&mask, SIGTTOU);
184 (void) sigprocmask(SIG_BLOCK, &mask, NULL);
189 * End window mode, which also resets the terminal state to the
190 * original (pre-curses) modes.
192 NCURSES_SP_NAME(endwin) (NCURSES_SP_ARG);
194 /* Unblock SIGTSTP. */
195 (void) sigemptyset(&mask);
196 (void) sigaddset(&mask, SIGTSTP);
198 if (!sigttou_blocked) {
199 /* Unblock this too if it wasn't blocked on entry */
200 (void) sigaddset(&mask, SIGTTOU);
203 (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
205 /* Now we want to resend SIGSTP to this process and suspend it */
206 act.sa_handler = SIG_DFL;
207 sigemptyset(&act.sa_mask);
210 act.sa_flags |= SA_RESTART;
211 #endif /* SA_RESTART */
212 sigaction(SIGTSTP, &act, &oact);
213 kill(getpid(), SIGTSTP);
215 /* Process gets suspended...time passes...process resumes */
217 T(("SIGCONT received"));
218 sigaction(SIGTSTP, &oact, NULL);
219 NCURSES_SP_NAME(flushinp) (NCURSES_SP_ARG);
222 * If the user modified the tty state while suspended, he wants
223 * those changes to stick. So save the new "default" terminal state.
225 NCURSES_SP_NAME(def_shell_mode) (NCURSES_SP_ARG);
228 * This relies on the fact that doupdate() will restore the
229 * program-mode tty state, and issue enter_ca_mode if need be.
231 NCURSES_SP_NAME(doupdate) (NCURSES_SP_ARG);
233 /* Reset the signals. */
234 (void) sigprocmask(SIG_SETMASK, &omask, NULL);
236 #endif /* USE_SIGTSTP */
239 handle_SIGINT(int sig)
241 SCREEN *sp = CURRENT_SCREEN;
244 * Much of this is unsafe from a signal handler. But we'll _try_ to clean
245 * up the screen and terminal settings on the way out.
247 * There are at least the following problems:
248 * 1) Walking the SCREEN list is unsafe, since all list management
249 * is done without any signal blocking.
250 * 2) On systems which have REENTRANT turned on, set_term() uses
251 * _nc_lock_global() which could deadlock or misbehave in other ways.
252 * 3) endwin() calls all sorts of stuff, many of which use stdio or
253 * other library functions which are clearly unsafe.
255 if (!_nc_globals.cleanup_nested++
256 && (sig == SIGINT || sig == SIGTERM)) {
257 #if HAVE_SIGACTION || HAVE_SIGVEC
259 sigemptyset(&act.sa_mask);
261 act.sa_handler = SIG_IGN;
262 if (sigaction(sig, &act, NULL) == 0)
264 if (signal(sig, SIG_IGN) != SIG_ERR)
268 for (each_screen(scan)) {
270 && NC_ISATTY(fileno(scan->_ofp))) {
271 scan->_outch = NCURSES_SP_NAME(_nc_outch);
274 NCURSES_SP_NAME(endwin) (NCURSES_SP_ARG);
276 sp->_endwin = FALSE; /* in case of reuse */
285 handle_SIGWINCH(int sig GCC_UNUSED)
287 _nc_globals.have_sigwinch = 1;
288 # if USE_PTHREADS_EINTR
289 if (_nc_globals.read_thread) {
290 if (!pthread_equal(pthread_self(), _nc_globals.read_thread))
291 pthread_kill(_nc_globals.read_thread, SIGWINCH);
292 _nc_globals.read_thread = 0;
296 #endif /* USE_SIGWINCH */
299 * If the given signal is still in its default state, set it to the given
303 CatchIfDefault(int sig, void (*handler) (int))
306 #if HAVE_SIGACTION || HAVE_SIGVEC
310 memset(&new_act, 0, sizeof(new_act));
311 sigemptyset(&new_act.sa_mask);
316 new_act.sa_flags |= SA_RESTART;
317 #endif /* SA_RESTART */
318 new_act.sa_handler = handler;
320 if (sigaction(sig, NULL, &old_act) == 0
321 && (old_act.sa_handler == SIG_DFL
322 || old_act.sa_handler == handler
324 || (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
327 (void) sigaction(sig, &new_act, NULL);
332 #else /* !HAVE_SIGACTION */
333 void (*ohandler) (int);
335 ohandler = signal(sig, SIG_IGN);
336 if (ohandler == SIG_DFL
337 || ohandler == handler
339 || (sig == SIGWINCH && ohandler == SIG_IGN)
342 signal(sig, handler);
345 signal(sig, ohandler);
349 T(("CatchIfDefault - will %scatch %s",
350 result ? "" : "not ", signal_name(sig)));
355 * This is invoked once at the beginning (e.g., from 'initscr()'), to
356 * initialize the signal catchers, and thereafter when spawning a shell (and
357 * returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
359 * If the application has already set one of the signals, we'll not modify it
360 * (during initialization).
362 * The XSI document implies that we shouldn't keep the SIGTSTP handler if
363 * the caller later changes its mind, but that doesn't seem correct.
366 _nc_signal_handler(int enable)
368 T((T_CALLED("_nc_signal_handler(%d)"), enable));
369 #if USE_SIGTSTP /* Xenix 2.x doesn't have SIGTSTP, for example */
371 static bool ignore_tstp = FALSE;
374 static sigaction_t new_sigaction, old_sigaction;
377 new_sigaction.sa_handler = SIG_IGN;
378 sigaction(SIGTSTP, &new_sigaction, &old_sigaction);
379 } else if (new_sigaction.sa_handler != SIG_DFL) {
380 sigaction(SIGTSTP, &old_sigaction, NULL);
381 } else if (sigaction(SIGTSTP, NULL, &old_sigaction) == 0
382 && (old_sigaction.sa_handler == SIG_DFL)) {
383 sigemptyset(&new_sigaction.sa_mask);
385 new_sigaction.sa_flags |= SA_RESTART;
386 #endif /* SA_RESTART */
387 new_sigaction.sa_handler = handle_SIGTSTP;
388 (void) sigaction(SIGTSTP, &new_sigaction, NULL);
394 #endif /* !USE_SIGTSTP */
396 if (!_nc_globals.init_signals) {
398 CatchIfDefault(SIGINT, handle_SIGINT);
399 CatchIfDefault(SIGTERM, handle_SIGINT);
401 CatchIfDefault(SIGWINCH, handle_SIGWINCH);
403 _nc_globals.init_signals = TRUE;