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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 1.41 2010/05/15 21:31:12 tom Exp $")
51 #if defined(SIGTSTP) && (HAVE_SIGACTION || HAVE_SIGVEC)
91 return "unknown signal";
97 * Note: This code is fragile! Its problem is that different OSs
98 * handle restart of system calls interrupted by signals differently.
99 * The ncurses code needs signal-call restart to happen -- otherwise,
100 * interrupted wgetch() calls will return FAIL, probably making the
101 * application think the input stream has ended and it should
102 * terminate. In particular, you know you have this problem if, when
103 * you suspend an ncurses-using lynx with ^Z and resume, it dies
106 * Default behavior of POSIX sigaction(2) is not to restart
107 * interrupted system calls, but Linux's sigaction does it anyway (at
108 * least, on and after the 1.1.47 I (esr) use). Thus this code works
109 * OK under Linux. The 4.4BSD sigaction(2) supports a (non-portable)
110 * SA_RESTART flag that forces the right behavior. Thus, this code
111 * should work OK under BSD/OS, NetBSD, and FreeBSD (let us know if it
114 * Stock System Vs (and anything else using a strict-POSIX
115 * sigaction(2) without SA_RESTART) may have a problem. Possible
118 * sigvec restarts by default (SV_INTERRUPT flag to not restart)
119 * signal restarts by default in SVr4 (assuming you link with -lucb)
120 * and BSD, but not SVr3.
121 * sigset restarts, but is only available under SVr4/Solaris.
123 * The signal(3) call is mandated by the ANSI standard, and its
124 * interaction with sigaction(2) is described in the POSIX standard
125 * (3.3.4.2, page 72,line 934). According to section 8.1, page 191,
126 * however, signal(3) itself is not required by POSIX.1. And POSIX is
127 * silent on whether it is required to restart signals.
129 * So. The present situation is, we use sigaction(2) with no
130 * guarantee of restart anywhere but on Linux and BSD. We could
131 * switch to signal(3) and collar Linux, BSD, and SVr4. Any way
132 * we slice it, System V UNIXes older than SVr4 will probably lose
133 * (this may include XENIX).
135 * This implementation will probably be changed to use signal(3) in
136 * the future. If nothing else, it's simpler...
141 tstp(int dummy GCC_UNUSED)
143 SCREEN *sp = CURRENT_SCREEN;
144 sigset_t mask, omask;
145 sigaction_t act, oact;
151 T(("tstp() called"));
154 * The user may have changed the prog_mode tty bits, so save them.
156 * But first try to detect whether we still are in the foreground
157 * process group - if not, an interactive shell may already have
158 * taken ownership of the tty and modified the settings when our
159 * parent was stopped before us, and we would likely pick up the
160 * settings already modified by the shell.
162 if (sp != 0 && !sp->_endwin) /* don't do this if we're not in curses */
164 if (tcgetpgrp(STDIN_FILENO) == getpgrp())
166 NCURSES_SP_NAME(def_prog_mode) (NCURSES_SP_ARG);
169 * Block window change and timer signals. The latter
170 * is because applications use timers to decide when
171 * to repaint the screen.
173 (void) sigemptyset(&mask);
175 (void) sigaddset(&mask, SIGALRM);
178 (void) sigaddset(&mask, SIGWINCH);
180 (void) sigprocmask(SIG_BLOCK, &mask, &omask);
183 sigttou_blocked = sigismember(&omask, SIGTTOU);
184 if (!sigttou_blocked) {
185 (void) sigemptyset(&mask);
186 (void) sigaddset(&mask, SIGTTOU);
187 (void) sigprocmask(SIG_BLOCK, &mask, NULL);
192 * End window mode, which also resets the terminal state to the
193 * original (pre-curses) modes.
195 NCURSES_SP_NAME(endwin) (NCURSES_SP_ARG);
197 /* Unblock SIGTSTP. */
198 (void) sigemptyset(&mask);
199 (void) sigaddset(&mask, SIGTSTP);
201 if (!sigttou_blocked) {
202 /* Unblock this too if it wasn't blocked on entry */
203 (void) sigaddset(&mask, SIGTTOU);
206 (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
208 /* Now we want to resend SIGSTP to this process and suspend it */
209 act.sa_handler = SIG_DFL;
210 sigemptyset(&act.sa_mask);
213 act.sa_flags |= SA_RESTART;
214 #endif /* SA_RESTART */
215 sigaction(SIGTSTP, &act, &oact);
216 kill(getpid(), SIGTSTP);
218 /* Process gets suspended...time passes...process resumes */
220 T(("SIGCONT received"));
221 sigaction(SIGTSTP, &oact, NULL);
222 NCURSES_SP_NAME(flushinp) (NCURSES_SP_ARG);
225 * If the user modified the tty state while suspended, he wants
226 * those changes to stick. So save the new "default" terminal state.
228 NCURSES_SP_NAME(def_shell_mode) (NCURSES_SP_ARG);
231 * This relies on the fact that doupdate() will restore the
232 * program-mode tty state, and issue enter_ca_mode if need be.
234 NCURSES_SP_NAME(doupdate) (NCURSES_SP_ARG);
236 /* Reset the signals. */
237 (void) sigprocmask(SIG_SETMASK, &omask, NULL);
239 #endif /* USE_SIGTSTP */
244 SCREEN *sp = CURRENT_SCREEN;
247 * Actually, doing any sort of I/O from within an signal handler is
248 * "unsafe". But we'll _try_ to clean up the screen and terminal
249 * settings on the way out.
251 if (!_nc_globals.cleanup_nested++
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 && isatty(fileno(scan->_ofp))) {
271 scan->_cleanup = TRUE;
272 scan->_outch = NCURSES_SP_NAME(_nc_outch);
275 NCURSES_SP_NAME(endwin) (NCURSES_SP_ARG);
277 sp->_endwin = FALSE; /* in case we have an atexit! */
286 sigwinch(int sig GCC_UNUSED)
288 _nc_globals.have_sigwinch = 1;
289 # if USE_PTHREADS_EINTR
290 if (_nc_globals.read_thread) {
291 if (!pthread_equal(pthread_self(), _nc_globals.read_thread))
292 pthread_kill(_nc_globals.read_thread, SIGWINCH);
293 _nc_globals.read_thread = 0;
297 #endif /* USE_SIGWINCH */
300 * If the given signal is still in its default state, set it to the given
304 CatchIfDefault(int sig, RETSIGTYPE (*handler) (int))
307 #if HAVE_SIGACTION || HAVE_SIGVEC
311 memset(&new_act, 0, sizeof(new_act));
312 sigemptyset(&new_act.sa_mask);
317 new_act.sa_flags |= SA_RESTART;
318 #endif /* SA_RESTART */
319 new_act.sa_handler = handler;
321 if (sigaction(sig, NULL, &old_act) == 0
322 && (old_act.sa_handler == SIG_DFL
323 || old_act.sa_handler == handler
325 || (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
328 (void) sigaction(sig, &new_act, NULL);
333 #else /* !HAVE_SIGACTION */
334 RETSIGTYPE (*ohandler) (int);
336 ohandler = signal(sig, SIG_IGN);
337 if (ohandler == SIG_DFL
338 || ohandler == handler
340 || (sig == SIGWINCH && ohandler == SIG_IGN)
343 signal(sig, handler);
346 signal(sig, ohandler);
350 T(("CatchIfDefault - will %scatch %s",
351 result ? "" : "not ", signal_name(sig)));
356 * This is invoked once at the beginning (e.g., from 'initscr()'), to
357 * initialize the signal catchers, and thereafter when spawning a shell (and
358 * returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
360 * If the application has already set one of the signals, we'll not modify it
361 * (during initialization).
363 * The XSI document implies that we shouldn't keep the SIGTSTP handler if
364 * the caller later changes its mind, but that doesn't seem correct.
367 _nc_signal_handler(bool enable)
369 T((T_CALLED("_nc_signal_handler(%d)"), enable));
370 #if USE_SIGTSTP /* Xenix 2.x doesn't have SIGTSTP, for example */
372 static bool ignore_tstp = FALSE;
375 static sigaction_t new_sigaction, old_sigaction;
378 new_sigaction.sa_handler = SIG_IGN;
379 sigaction(SIGTSTP, &new_sigaction, &old_sigaction);
380 } else if (new_sigaction.sa_handler != SIG_DFL) {
381 sigaction(SIGTSTP, &old_sigaction, NULL);
382 } else if (sigaction(SIGTSTP, NULL, &old_sigaction) == 0
383 && (old_sigaction.sa_handler == SIG_DFL)) {
384 sigemptyset(&new_sigaction.sa_mask);
386 new_sigaction.sa_flags |= SA_RESTART;
387 #endif /* SA_RESTART */
388 new_sigaction.sa_handler = tstp;
389 (void) sigaction(SIGTSTP, &new_sigaction, NULL);
395 #endif /* !USE_SIGTSTP */
397 if (!_nc_globals.init_signals) {
399 CatchIfDefault(SIGINT, cleanup);
400 CatchIfDefault(SIGTERM, cleanup);
402 CatchIfDefault(SIGWINCH, sigwinch);
404 _nc_globals.init_signals = TRUE;