Adding upstream version 5.0.upstream/5.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 782 insertions, 0 deletions

diff --git a/sig.c b/sig.c
new file mode 100644
index 0000000..f8a0e0f
--- /dev/null
+++ b/sig.c
@@ -0,0 +1,782 @@
+/* sig.c - interface for shell signal handlers and signal initialization. */
+
+/* Copyright (C) 1994-2018 Free Software Foundation, Inc.
+
+   This file is part of GNU Bash, the Bourne Again SHell.
+
+   Bash is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   Bash is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Bash.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "config.h"
+
+#include "bashtypes.h"
+
+#if defined (HAVE_UNISTD_H)
+#  ifdef _MINIX
+#    include <sys/types.h>
+#  endif
+#  include <unistd.h>
+#endif
+
+#include <stdio.h>
+#include <signal.h>
+
+#include "bashintl.h"
+
+#include "shell.h"
+#include "execute_cmd.h"
+#if defined (JOB_CONTROL)
+#include "jobs.h"
+#endif /* JOB_CONTROL */
+#include "siglist.h"
+#include "sig.h"
+#include "trap.h"
+
+#include "builtins/common.h"
+#include "builtins/builtext.h"
+
+#if defined (READLINE)
+#  include "bashline.h"
+#  include <readline/readline.h>
+#endif
+
+#if defined (HISTORY)
+#  include "bashhist.h"
+#endif
+
+extern void initialize_siglist ();
+
+#if !defined (JOB_CONTROL)
+extern void initialize_job_signals __P((void));
+#endif
+
+/* Non-zero after SIGINT. */
+volatile sig_atomic_t interrupt_state = 0;
+
+/* Non-zero after SIGWINCH */
+volatile sig_atomic_t sigwinch_received = 0;
+
+/* Non-zero after SIGTERM */
+volatile sig_atomic_t sigterm_received = 0;
+
+/* Set to the value of any terminating signal received. */
+volatile sig_atomic_t terminating_signal = 0;
+
+/* The environment at the top-level R-E loop.  We use this in
+   the case of error return. */
+procenv_t top_level;
+
+#if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
+/* The signal masks that this shell runs with. */
+sigset_t top_level_mask;
+#endif /* JOB_CONTROL */
+
+/* When non-zero, we throw_to_top_level (). */
+int interrupt_immediately = 0;
+
+/* When non-zero, we call the terminating signal handler immediately. */
+int terminate_immediately = 0;
+
+#if defined (SIGWINCH)
+static SigHandler *old_winch = (SigHandler *)SIG_DFL;
+#endif
+
+static void initialize_shell_signals __P((void));
+
+void
+initialize_signals (reinit)
+     int reinit;
+{
+  initialize_shell_signals ();
+  initialize_job_signals ();
+#if !defined (HAVE_SYS_SIGLIST) && !defined (HAVE_UNDER_SYS_SIGLIST) && !defined (HAVE_STRSIGNAL)
+  if (reinit == 0)
+    initialize_siglist ();
+#endif /* !HAVE_SYS_SIGLIST && !HAVE_UNDER_SYS_SIGLIST && !HAVE_STRSIGNAL */
+}
+
+/* A structure describing a signal that terminates the shell if not
+   caught.  The orig_handler member is present so children can reset
+   these signals back to their original handlers. */
+struct termsig {
+     int signum;
+     SigHandler *orig_handler;
+     int orig_flags;
+     int core_dump;
+};
+
+#define NULL_HANDLER (SigHandler *)SIG_DFL
+
+/* The list of signals that would terminate the shell if not caught.
+   We catch them, but just so that we can write the history file,
+   and so forth. */
+static struct termsig terminating_signals[] = {
+#ifdef SIGHUP
+{  SIGHUP, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGINT
+{  SIGINT, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGILL
+{  SIGILL, NULL_HANDLER, 0, 1},
+#endif
+
+#ifdef SIGTRAP
+{  SIGTRAP, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGIOT
+{  SIGIOT, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGDANGER
+{  SIGDANGER, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGEMT
+{  SIGEMT, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGFPE
+{  SIGFPE, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGBUS
+{  SIGBUS, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGSEGV
+{  SIGSEGV, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGSYS
+{  SIGSYS, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGPIPE
+{  SIGPIPE, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGALRM
+{  SIGALRM, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGTERM
+{  SIGTERM, NULL_HANDLER, 0 },
+#endif
+
+/* These don't generate core dumps on anything but Linux, but we're doing
+   this just for Linux anyway. */
+#ifdef SIGXCPU
+{  SIGXCPU, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGXFSZ
+{  SIGXFSZ, NULL_HANDLER, 0, 1 },
+#endif
+
+#ifdef SIGVTALRM
+{  SIGVTALRM, NULL_HANDLER, 0 },
+#endif
+
+#if 0
+#ifdef SIGPROF
+{  SIGPROF, NULL_HANDLER, 0 },
+#endif
+#endif
+
+#ifdef SIGLOST
+{  SIGLOST, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGUSR1
+{  SIGUSR1, NULL_HANDLER, 0 },
+#endif
+
+#ifdef SIGUSR2
+{  SIGUSR2, NULL_HANDLER, 0 },
+#endif
+};
+
+#define TERMSIGS_LENGTH (sizeof (terminating_signals) / sizeof (struct termsig))
+
+#define XSIG(x) (terminating_signals[x].signum)
+#define XHANDLER(x) (terminating_signals[x].orig_handler)
+#define XSAFLAGS(x) (terminating_signals[x].orig_flags)
+#define XCOREDUMP(x) (terminating_signals[x].core_dump)
+
+static int termsigs_initialized = 0;
+
+/* Initialize signals that will terminate the shell to do some
+   unwind protection.  For non-interactive shells, we only call
+   this when a trap is defined for EXIT (0) or when trap is run
+   to display signal dispositions. */
+void
+initialize_terminating_signals ()
+{
+  register int i;
+#if defined (HAVE_POSIX_SIGNALS)
+  struct sigaction act, oact;
+#endif
+
+  if (termsigs_initialized)
+    return;
+
+  /* The following code is to avoid an expensive call to
+     set_signal_handler () for each terminating_signals.  Fortunately,
+     this is possible in Posix.  Unfortunately, we have to call signal ()
+     on non-Posix systems for each signal in terminating_signals. */
+#if defined (HAVE_POSIX_SIGNALS)
+  act.sa_handler = termsig_sighandler;
+  act.sa_flags = 0;
+  sigemptyset (&act.sa_mask);
+  sigemptyset (&oact.sa_mask);
+  for (i = 0; i < TERMSIGS_LENGTH; i++)
+    sigaddset (&act.sa_mask, XSIG (i));
+  for (i = 0; i < TERMSIGS_LENGTH; i++)
+    {
+      /* If we've already trapped it, don't do anything. */
+      if (signal_is_trapped (XSIG (i)))
+	continue;
+
+      sigaction (XSIG (i), &act, &oact);
+      XHANDLER(i) = oact.sa_handler;
+      XSAFLAGS(i) = oact.sa_flags;
+      /* Don't do anything with signals that are ignored at shell entry
+	 if the shell is not interactive. */
+      /* XXX - should we do this for interactive shells, too? */
+      if (interactive_shell == 0 && XHANDLER (i) == SIG_IGN)
+	{
+	  sigaction (XSIG (i), &oact, &act);
+	  set_signal_hard_ignored (XSIG (i));
+	}
+#if defined (SIGPROF) && !defined (_MINIX)
+      if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
+	sigaction (XSIG (i), &oact, (struct sigaction *)NULL);
+#endif /* SIGPROF && !_MINIX */
+    }
+#else /* !HAVE_POSIX_SIGNALS */
+
+  for (i = 0; i < TERMSIGS_LENGTH; i++)
+    {
+      /* If we've already trapped it, don't do anything. */
+      if (signal_is_trapped (XSIG (i)))
+	continue;
+
+      XHANDLER(i) = signal (XSIG (i), termsig_sighandler);
+      XSAFLAGS(i) = 0;
+      /* Don't do anything with signals that are ignored at shell entry
+	 if the shell is not interactive. */
+      /* XXX - should we do this for interactive shells, too? */
+      if (interactive_shell == 0 && XHANDLER (i) == SIG_IGN)
+	{
+	  signal (XSIG (i), SIG_IGN);
+	  set_signal_hard_ignored (XSIG (i));
+	}
+#ifdef SIGPROF
+      if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
+	signal (XSIG (i), XHANDLER (i));
+#endif
+    }
+
+#endif /* !HAVE_POSIX_SIGNALS */
+
+  termsigs_initialized = 1;
+}
+
+static void
+initialize_shell_signals ()
+{
+  if (interactive)
+    initialize_terminating_signals ();
+
+#if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
+  /* All shells use the signal mask they inherit, and pass it along
+     to child processes.  Children will never block SIGCHLD, though. */
+  sigemptyset (&top_level_mask);
+  sigprocmask (SIG_BLOCK, (sigset_t *)NULL, &top_level_mask);
+#  if defined (SIGCHLD)
+  sigdelset (&top_level_mask, SIGCHLD);
+#  endif
+#endif /* JOB_CONTROL || HAVE_POSIX_SIGNALS */
+
+  /* And, some signals that are specifically ignored by the shell. */
+  set_signal_handler (SIGQUIT, SIG_IGN);
+
+  if (interactive)
+    {
+      set_signal_handler (SIGINT, sigint_sighandler);
+      get_original_signal (SIGTERM);
+      if (signal_is_hard_ignored (SIGTERM) == 0)
+	set_signal_handler (SIGTERM, sigterm_sighandler);
+      set_sigwinch_handler ();
+    }
+}
+
+void
+reset_terminating_signals ()
+{
+  register int i;
+#if defined (HAVE_POSIX_SIGNALS)
+  struct sigaction act;
+#endif
+
+  if (termsigs_initialized == 0)
+    return;
+
+#if defined (HAVE_POSIX_SIGNALS)
+  act.sa_flags = 0;
+  sigemptyset (&act.sa_mask);
+  for (i = 0; i < TERMSIGS_LENGTH; i++)
+    {
+      /* Skip a signal if it's trapped or handled specially, because the
+	 trap code will restore the correct value. */
+      if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
+	continue;
+
+      act.sa_handler = XHANDLER (i);
+      act.sa_flags = XSAFLAGS (i);
+      sigaction (XSIG (i), &act, (struct sigaction *) NULL);
+    }
+#else /* !HAVE_POSIX_SIGNALS */
+  for (i = 0; i < TERMSIGS_LENGTH; i++)
+    {
+      if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
+	continue;
+
+      signal (XSIG (i), XHANDLER (i));
+    }
+#endif /* !HAVE_POSIX_SIGNALS */
+
+  termsigs_initialized = 0;
+}
+#undef XHANDLER
+
+/* Run some of the cleanups that should be performed when we run
+   jump_to_top_level from a builtin command context.  XXX - might want to
+   also call reset_parser here. */
+void
+top_level_cleanup ()
+{
+  /* Clean up string parser environment. */
+  while (parse_and_execute_level)
+    parse_and_execute_cleanup (-1);
+
+#if defined (PROCESS_SUBSTITUTION)
+  unlink_fifo_list ();
+#endif /* PROCESS_SUBSTITUTION */
+
+  run_unwind_protects ();
+  loop_level = continuing = breaking = funcnest = 0;
+  executing_list = comsub_ignore_return = return_catch_flag = wait_intr_flag = 0;
+}
+
+/* What to do when we've been interrupted, and it is safe to handle it. */
+void
+throw_to_top_level ()
+{
+  int print_newline = 0;
+
+  if (interrupt_state)
+    {
+      if (last_command_exit_value < 128)
+	last_command_exit_value = 128 + SIGINT;
+      print_newline = 1;
+      DELINTERRUPT;
+    }
+
+  if (interrupt_state)
+    return;
+
+  last_command_exit_signal = (last_command_exit_value > 128) ?
+				(last_command_exit_value - 128) : 0;
+  last_command_exit_value |= 128;
+
+  /* Run any traps set on SIGINT, mostly for interactive shells */
+  if (signal_is_trapped (SIGINT))
+    run_interrupt_trap (1);
+
+  /* Clean up string parser environment. */
+  while (parse_and_execute_level)
+    parse_and_execute_cleanup (-1);
+
+  if (running_trap > 0)
+    run_trap_cleanup (running_trap - 1);
+
+#if defined (JOB_CONTROL)
+  give_terminal_to (shell_pgrp, 0);
+#endif /* JOB_CONTROL */
+
+#if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
+  /* This needs to stay because jobs.c:make_child() uses it without resetting
+     the signal mask. */
+  sigprocmask (SIG_SETMASK, &top_level_mask, (sigset_t *)NULL);
+#endif
+
+  reset_parser ();
+
+#if defined (READLINE)
+  if (interactive)
+    bashline_reset ();
+#endif /* READLINE */
+
+#if defined (PROCESS_SUBSTITUTION)
+  unlink_fifo_list ();
+#endif /* PROCESS_SUBSTITUTION */
+
+  run_unwind_protects ();
+  loop_level = continuing = breaking = funcnest = 0;
+  executing_list = comsub_ignore_return = return_catch_flag = wait_intr_flag = 0;
+
+  if (interactive && print_newline)
+    {
+      fflush (stdout);
+      fprintf (stderr, "\n");
+      fflush (stderr);
+    }
+
+  /* An interrupted `wait' command in a script does not exit the script. */
+  if (interactive || (interactive_shell && !shell_initialized) ||
+      (print_newline && signal_is_trapped (SIGINT)))
+    jump_to_top_level (DISCARD);
+  else
+    jump_to_top_level (EXITPROG);
+}
+
+/* This is just here to isolate the longjmp calls. */
+void
+jump_to_top_level (value)
+     int value;
+{
+  sh_longjmp (top_level, value);
+}
+
+sighandler
+termsig_sighandler (sig)
+     int sig;
+{
+  /* If we get called twice with the same signal before handling it,
+     terminate right away. */
+  if (
+#ifdef SIGHUP
+    sig != SIGHUP &&
+#endif
+#ifdef SIGINT
+    sig != SIGINT &&
+#endif
+#ifdef SIGDANGER
+    sig != SIGDANGER &&
+#endif
+#ifdef SIGPIPE
+    sig != SIGPIPE &&
+#endif
+#ifdef SIGALRM
+    sig != SIGALRM &&
+#endif
+#ifdef SIGTERM
+    sig != SIGTERM &&
+#endif
+#ifdef SIGXCPU
+    sig != SIGXCPU &&
+#endif
+#ifdef SIGXFSZ
+    sig != SIGXFSZ &&
+#endif
+#ifdef SIGVTALRM
+    sig != SIGVTALRM &&
+#endif
+#ifdef SIGLOST
+    sig != SIGLOST &&
+#endif
+#ifdef SIGUSR1
+    sig != SIGUSR1 &&
+#endif
+#ifdef SIGUSR2
+   sig != SIGUSR2 &&
+#endif
+   sig == terminating_signal)
+    terminate_immediately = 1;
+
+  terminating_signal = sig;
+
+  /* XXX - should this also trigger when interrupt_immediately is set? */
+  if (terminate_immediately)
+    {
+#if defined (HISTORY)
+      /* XXX - will inhibit history file being written */
+#  if defined (READLINE)
+      if (interactive_shell == 0 || interactive == 0 || (sig != SIGHUP && sig != SIGTERM) || no_line_editing || (RL_ISSTATE (RL_STATE_READCMD) == 0))
+#  endif
+        history_lines_this_session = 0;
+#endif
+      terminate_immediately = 0;
+      termsig_handler (sig);
+    }
+
+#if defined (READLINE)
+  /* Set the event hook so readline will call it after the signal handlers
+     finish executing, so if this interrupted character input we can get
+     quick response.  If readline is active or has modified the terminal we
+     need to set this no matter what the signal is, though the check for
+     RL_STATE_TERMPREPPED is possibly redundant. */
+  if (RL_ISSTATE (RL_STATE_SIGHANDLER) || RL_ISSTATE (RL_STATE_TERMPREPPED))
+    bashline_set_event_hook ();
+#endif
+
+  SIGRETURN (0);
+}
+
+void
+termsig_handler (sig)
+     int sig;
+{
+  static int handling_termsig = 0;
+  int i, core;
+  sigset_t mask;
+
+  /* Simple semaphore to keep this function from being executed multiple
+     times.  Since we no longer are running as a signal handler, we don't
+     block multiple occurrences of the terminating signals while running. */
+  if (handling_termsig)
+    return;
+  handling_termsig = 1;
+  terminating_signal = 0;	/* keep macro from re-testing true. */
+
+  /* I don't believe this condition ever tests true. */
+  if (sig == SIGINT && signal_is_trapped (SIGINT))
+    run_interrupt_trap (0);
+
+#if defined (HISTORY)
+  /* If we don't do something like this, the history will not be saved when
+     an interactive shell is running in a terminal window that gets closed
+     with the `close' button.  We can't test for RL_STATE_READCMD because
+     readline no longer handles SIGTERM synchronously.  */
+  if (interactive_shell && interactive && (sig == SIGHUP || sig == SIGTERM) && remember_on_history)
+    maybe_save_shell_history ();
+#endif /* HISTORY */
+
+  if (this_shell_builtin == read_builtin)
+    read_tty_cleanup ();
+
+#if defined (JOB_CONTROL)
+  if (sig == SIGHUP && (interactive || (subshell_environment & (SUBSHELL_COMSUB|SUBSHELL_PROCSUB))))
+    hangup_all_jobs ();
+
+  if ((subshell_environment & (SUBSHELL_COMSUB|SUBSHELL_PROCSUB)) == 0)
+    end_job_control ();
+#endif /* JOB_CONTROL */
+
+#if defined (PROCESS_SUBSTITUTION)
+  unlink_fifo_list ();
+#endif /* PROCESS_SUBSTITUTION */
+
+  /* Reset execution context */
+  loop_level = continuing = breaking = funcnest = 0;
+  executing_list = comsub_ignore_return = return_catch_flag = wait_intr_flag = 0;
+
+  run_exit_trap ();	/* XXX - run exit trap possibly in signal context? */
+
+  /* We don't change the set of blocked signals. If a user starts the shell
+     with a terminating signal blocked, we won't get here (and if by some
+     magic chance we do, we'll exit below). */
+  set_signal_handler (sig, SIG_DFL);
+
+  kill (getpid (), sig);
+
+  if (dollar_dollar_pid != 1)
+    exit (128+sig);		/* just in case the kill fails? */
+
+  /* We get here only under extraordinary circumstances. */
+
+  /* We are PID 1, and the kill above failed to kill the process. We assume
+     this means that we are running as an init process in a pid namespace
+     on Linux. In this case, we can't send ourselves a fatal signal, so we
+     determine whether or not we should have generated a core dump with the
+     kill call and attempt to trick the kernel into generating one if
+     necessary. */
+  sigprocmask (SIG_SETMASK, (sigset_t *)NULL, &mask);
+  for (i = core = 0; i < TERMSIGS_LENGTH; i++)
+    {
+      set_signal_handler (XSIG (i), SIG_DFL);
+      sigdelset (&mask, XSIG (i));
+      if (sig == XSIG (i))
+	core = XCOREDUMP (i);
+    }
+  sigprocmask (SIG_SETMASK, &mask, (sigset_t *)NULL);
+
+  if (core)
+    *((volatile unsigned long *) NULL) = 0xdead0000 + sig;	/* SIGSEGV */
+
+  exit (128+sig);
+}
+#undef XSIG
+
+/* What we really do when SIGINT occurs. */
+sighandler
+sigint_sighandler (sig)
+     int sig;
+{
+#if defined (MUST_REINSTALL_SIGHANDLERS)
+  signal (sig, sigint_sighandler);
+#endif
+
+  /* interrupt_state needs to be set for the stack of interrupts to work
+     right.  Should it be set unconditionally? */
+  if (interrupt_state == 0)
+    ADDINTERRUPT;
+
+  /* We will get here in interactive shells with job control active; allow
+     an interactive wait to be interrupted.  wait_intr_flag is only set during
+     the execution of the wait builtin and when wait_intr_buf is valid. */
+  if (wait_intr_flag)
+    {
+      last_command_exit_value = 128 + sig;
+      wait_signal_received = sig;
+      SIGRETURN (0);
+    }
+      
+  if (interrupt_immediately)
+    {
+      interrupt_immediately = 0;
+      last_command_exit_value = 128 + sig;
+      throw_to_top_level ();
+    }
+#if defined (READLINE)
+  /* Set the event hook so readline will call it after the signal handlers
+     finish executing, so if this interrupted character input we can get
+     quick response. */
+  else if (RL_ISSTATE (RL_STATE_SIGHANDLER))
+    bashline_set_event_hook ();
+#endif
+
+  SIGRETURN (0);
+}
+
+#if defined (SIGWINCH)
+sighandler
+sigwinch_sighandler (sig)
+     int sig;
+{
+#if defined (MUST_REINSTALL_SIGHANDLERS)
+  set_signal_handler (SIGWINCH, sigwinch_sighandler);
+#endif /* MUST_REINSTALL_SIGHANDLERS */
+  sigwinch_received = 1;
+  SIGRETURN (0);
+}
+#endif /* SIGWINCH */
+
+void
+set_sigwinch_handler ()
+{
+#if defined (SIGWINCH)
+ old_winch = set_signal_handler (SIGWINCH, sigwinch_sighandler);
+#endif
+}
+
+void
+unset_sigwinch_handler ()
+{
+#if defined (SIGWINCH)
+  set_signal_handler (SIGWINCH, old_winch);
+#endif
+}
+
+sighandler
+sigterm_sighandler (sig)
+     int sig;
+{
+  sigterm_received = 1;		/* XXX - counter? */
+  SIGRETURN (0);
+}
+
+/* Signal functions used by the rest of the code. */
+#if !defined (HAVE_POSIX_SIGNALS)
+
+/* Perform OPERATION on NEWSET, perhaps leaving information in OLDSET. */
+sigprocmask (operation, newset, oldset)
+     int operation, *newset, *oldset;
+{
+  int old, new;
+
+  if (newset)
+    new = *newset;
+  else
+    new = 0;
+
+  switch (operation)
+    {
+    case SIG_BLOCK:
+      old = sigblock (new);
+      break;
+
+    case SIG_SETMASK:
+      old = sigsetmask (new);
+      break;
+
+    default:
+      internal_error (_("sigprocmask: %d: invalid operation"), operation);
+    }
+
+  if (oldset)
+    *oldset = old;
+}
+
+#else
+
+#if !defined (SA_INTERRUPT)
+#  define SA_INTERRUPT 0
+#endif
+
+#if !defined (SA_RESTART)
+#  define SA_RESTART 0
+#endif
+
+SigHandler *
+set_signal_handler (sig, handler)
+     int sig;
+     SigHandler *handler;
+{
+  struct sigaction act, oact;
+
+  act.sa_handler = handler;
+  act.sa_flags = 0;
+
+  /* XXX - bash-4.2 */
+  /* We don't want a child death to interrupt interruptible system calls, even
+     if we take the time to reap children */
+#if defined (SIGCHLD)
+  if (sig == SIGCHLD)
+    act.sa_flags |= SA_RESTART;		/* XXX */
+#endif
+  /* Let's see if we can keep SIGWINCH from interrupting interruptible system
+     calls, like open(2)/read(2)/write(2) */
+#if defined (SIGWINCH)
+  if (sig == SIGWINCH)
+    act.sa_flags |= SA_RESTART;		/* XXX */
+#endif
+  /* If we're installing a SIGTERM handler for interactive shells, we want
+     it to be as close to SIG_IGN as possible. */
+  if (sig == SIGTERM && handler == sigterm_sighandler)
+    act.sa_flags |= SA_RESTART;		/* XXX */
+
+  sigemptyset (&act.sa_mask);
+  sigemptyset (&oact.sa_mask);
+  if (sigaction (sig, &act, &oact) == 0)
+    return (oact.sa_handler);
+  else
+    return (SIG_DFL);
+}
+#endif /* HAVE_POSIX_SIGNALS */