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Diffstat (limited to 'lib/libcurses/lib_tstp.c')
| -rw-r--r-- | lib/libcurses/lib_tstp.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/lib/libcurses/lib_tstp.c b/lib/libcurses/lib_tstp.c new file mode 100644 index 00000000000..73be68af51c --- /dev/null +++ b/lib/libcurses/lib_tstp.c @@ -0,0 +1,252 @@ + +/*************************************************************************** +* COPYRIGHT NOTICE * +**************************************************************************** +* ncurses is copyright (C) 1992-1995 * +* Zeyd M. Ben-Halim * +* zmbenhal@netcom.com * +* Eric S. Raymond * +* esr@snark.thyrsus.com * +* * +* Permission is hereby granted to reproduce and distribute ncurses * +* by any means and for any fee, whether alone or as part of a * +* larger distribution, in source or in binary form, PROVIDED * +* this notice is included with any such distribution, and is not * +* removed from any of its header files. Mention of ncurses in any * +* applications linked with it is highly appreciated. * +* * +* ncurses comes AS IS with no warranty, implied or expressed. * +* * +***************************************************************************/ + + +/* +** lib_tstp.c +** +** The routine _nc_signal_handler(). +** +*/ + +#include "curses.priv.h" + +#include <signal.h> +#include <stdlib.h> + +#if HAVE_SIGACTION +#if !HAVE_TYPE_SIGACTION +typedef struct sigaction sigaction_t; +#endif +#else +#include "SigAction.h" +#endif + +#ifdef SVR4_ACTION +#define _POSIX_SOURCE +#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... + */ + +#ifdef SIGTSTP +static void tstp(int dummy) +{ + sigset_t mask, omask; + sigaction_t act, oact; + + T(("tstp() called")); + + /* + * The user may have changed the prog_mode tty bits, so save them. + */ + 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); +#ifdef SIGWINCH + (void)sigaddset(&mask, SIGWINCH); +#endif + (void)sigprocmask(SIG_BLOCK, &mask, &omask); + + /* + * 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); + (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 /* defined(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 (sig == SIGINT + || sig == SIGQUIT) { + sigaction_t act; + sigemptyset(&act.sa_mask); + act.sa_flags = 0; + act.sa_handler = SIG_IGN; + if (sigaction(sig, &act, (sigaction_t *)0) == 0) { + endwin(); + } + } + exit(1); +} + +/* + * If the given signal is still in its default state, set it to the given + * handler. + */ +static int CatchIfDefault(int sig, sigaction_t *act) +{ + sigaction_t old_act; + +#ifdef SA_RESTART + act->sa_flags |= SA_RESTART; +#endif /* SA_RESTART */ + if (sigaction(sig, (sigaction_t *)0, &old_act) == 0 + && old_act.sa_handler == SIG_DFL) { + (void)sigaction(sig, act, (sigaction_t *)0); + return TRUE; + } + return FALSE; +} + +/* + * 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. + */ +void _nc_signal_handler(bool enable) +{ +#ifdef SIGTSTP /* Xenix 2.x doesn't have this */ +static sigaction_t act, oact; +static int ignore; + + if (!ignore) + { + if (!enable) + { + act.sa_handler = SIG_IGN; + sigaction(SIGTSTP, &act, &oact); + } + else if (act.sa_handler) + { + sigaction(SIGTSTP, &oact, NULL); + } + else /*initialize */ + { + sigemptyset(&act.sa_mask); + act.sa_flags = 0; +#ifdef SA_RESTART + act.sa_flags |= SA_RESTART; +#endif /* SA_RESTART */ + + act.sa_handler = cleanup; + CatchIfDefault(SIGINT, &act); + CatchIfDefault(SIGTERM, &act); + + act.sa_handler = tstp; + if (!CatchIfDefault(SIGTSTP, &act)) + ignore = TRUE; + } + } +#else + if (enable) + { + static sigaction_t act; + act.sa_handler = cleanup; + CatchIfDefault(SIGINT, &act); + CatchIfDefault(SIGTERM, &act); + } +#endif +} |