Signal-handler cleanup.

Emacs's signal handlers were written in the old 4.2BSD style with
sigblock and sigmask and so forth, and this led to some
inefficiencies and confusion.  Rewrite these to use
pthread_sigmask etc. without copying signal sets around.  Also,
get rid of the confusing macros 'SIGNAL_THREAD_CHECK' and
'signal', and instead use functions that do not attempt to take
over the system name space.  This patch causes Emacs's text
segment to shrink by 0.7% on my platform, Fedora 17 x86-64.
* configure.ac (PTY_OPEN, PTY_TTY_NAME_SPRINTF):
Adjust to syssignal.h changes.
(SIGNAL_H_AB): Remove; no longer needed.
* src/alloc.c, src/emacsgtkfixed.c, src/nsfns.m, src/widget.c, src/xmenu.c:
Do not include <signal.h> or "syssignal.h", as these
modules do not use signals.
* src/atimer.c, src/callproc.c, src/data.c, src/dispnew.c, src/emacs.c:
* src/floatfns.c, src/gtkutil.c, src/keyboard.c, src/process.c, src/sound.c:
* src/sysdep.c, src/term.c, src/xterm.c:
Do not include <signal.h>, as "syssignal.h" does that for us now.
* src/atimer.c (sigmask_atimers): New function.
(block_atimers, unblock_atimers): New functions,
replacing the old macros BLOCK_ATIMERS and UNBLOCK_ATIMERS.
All uses replaced.
* src/conf_post.h [SIGNAL_H_AHB]: Do not include <signal.h>;
no longer needed here.
* src/emacs.c (main): Inspect existing signal handler with sigaction,
so that there's	no need to block and unblock SIGHUP.
* src/sysdep.c (struct save_signal): New member 'action', replacing
old member 'handler'.
(save_signal_handlers, restore_signal_handlers):
Use sigaction instead of 'signal' to save and restore.
(get_set_sighandler, set_sighandler) [!WINDOWSNT]:
New function.  All users of 'signal' modified to use set_sighandler
if they're writeonly, and to use sys_signal if they're read+write.
(emacs_sigaction_init, forwarded_signal): New functions.
(sys_signal): Remove.  All uses replaced by calls to sigaction
and emacs_sigaction_init, or by direct calls to 'signal'.
(sys_sigmask) [!__GNUC__]: Remove; no longer needed.
(sys_sigblock, sys_sigunblock, sys_sigsetmask): Remove;
all uses replaced by pthread_sigmask etc. calls.
* src/syssignal.h: Include <signal.h>.
(emacs_sigaction_init, forwarded_signal): New decls.
(SIGMASKTYPE): Remove.  All uses replaced by its definiens, sigset_t.
(SIGEMPTYMASK): Remove; all uses replaced by its definiens, empty_mask.
(sigmask, sys_sigmask): Remove; no longer needed.
(sigpause): Remove.  All uses replaced by its definiens, sigsuspend.
(sigblock, sigunblock, sigfree):
(sigsetmask) [!defined sigsetmask]:
Remove.  All uses replaced by pthread_sigmask.
(signal): Remove.  Its remaining uses (with SIG_DFL and SIG_IGN)
no longer need to be replaced, and its typical old uses
are now done via emacs_sigaction_init and sigaction.
(sys_sigblock, sys_sigunblock, sys_sigsetmask): Remove decls.
(sys_sigdel): Remove; unused.
(NSIG): Remove a FIXME; the code's fine.  Remove an unnecessary ifdef.

Fixes: debbugs:12327

23 files changed, 325 insertions, 283 deletions

diff --git a/ChangeLog b/ChangeLog
index 55223ab8c5e..112532e7ece 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2012-09-06  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Signal-handler cleanup (Bug#12327).
+        * configure.ac (PTY_OPEN, PTY_TTY_NAME_SPRINTF):
+        Adjust to syssignal.h changes.
+        (SIGNAL_H_AB): Remove; no longer needed.
+
 2012-09-04  Paul Eggert  <eggert@cs.ucla.edu>
 
         Simplify redefinition of 'abort' (Bug#12316).
diff --git a/configure.ac b/configure.ac
index 16e579c862a..dd5e322194a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3445,7 +3445,7 @@ case $opsys in
   cygwin )
     AC_DEFINE(PTY_ITERATION, [int i; for (i = 0; i < 1; i++)])
     dnl multi-line AC_DEFINEs are hard. :(
-    AC_DEFINE(PTY_OPEN, [ do { int dummy; SIGMASKTYPE mask; mask = sigblock (sigmask (SIGCHLD)); if (-1 == openpty (&fd, &dummy, pty_name, 0, 0)) fd = -1; sigsetmask (mask); if (fd >= 0) emacs_close (dummy); } while (0)])
+    AC_DEFINE(PTY_OPEN, [ do { int dummy; sigset_t blocked, procmask; sigemptyset (&blocked); sigaddset (&blocked, SIGCHLD); pthread_sigmask (SIG_BLOCK, &blocked, &procmask); if (-1 == openpty (&fd, &dummy, pty_name, 0, 0)) fd = -1; pthread_sigmask (SIG_SETMASK, &procmask, 0); if (fd >= 0) emacs_close (dummy); } while (0)])
     AC_DEFINE(PTY_NAME_SPRINTF, [])
     AC_DEFINE(PTY_TTY_NAME_SPRINTF, [])
     ;;
@@ -3474,7 +3474,7 @@ case $opsys in
       AC_DEFINE(PTY_ITERATION, [int i; for (i = 0; i < 1; i++)])
       dnl Note that grantpt and unlockpt may fork.  We must block SIGCHLD
       dnl to prevent sigchld_handler from intercepting the child's death.
-      AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptyname; sigblock (sigmask (SIGCHLD)); if (grantpt (fd) == -1 || unlockpt (fd) == -1 || !(ptyname = ptsname(fd))) { sigunblock (sigmask (SIGCHLD)); close (fd); return -1; } snprintf (pty_name, sizeof pty_name, "%s", ptyname); sigunblock (sigmask (SIGCHLD)); }])
+      AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptyname = 0; sigset_t blocked; sigemptyset (&blocked); sigaddset (&blocked, SIGCHLD); pthread_sigmask (SIG_BLOCK, &blocked, 0); if (grantpt (fd) != -1 && unlockpt (fd) != -1) ptyname = ptsname(fd); pthread_sigmask (SIG_UNBLOCK, &blocked, 0); if (!ptyname) { close (fd); return -1; } snprintf (pty_name, sizeof pty_name, "%s", ptyname); }])
       dnl if HAVE_POSIX_OPENPT
       if test "x$ac_cv_func_posix_openpt" = xyes; then
         AC_DEFINE(PTY_OPEN, [fd = posix_openpt (O_RDWR | O_NOCTTY)])
@@ -3519,18 +3519,15 @@ case $opsys in
     ;;
 
   sol2* )
-    dnl Uses sigblock/sigunblock rather than sighold/sigrelse,
-    dnl which appear to be BSD4.1 specific.  It may also be appropriate
-    dnl for SVR4.x (x<2) but I'm not sure.   fnf@cygnus.com
     dnl On SysVr4, grantpt(3) forks a subprocess, so keep sigchld_handler()
     dnl from intercepting that death.  If any child but grantpt's should die
     dnl within, it should be caught after sigrelse(2).
-    AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptsname (int), *ptyname; sigblock (sigmask (SIGCLD)); if (grantpt (fd) == -1) { emacs_close (fd); return -1; } sigunblock (sigmask (SIGCLD)); if (unlockpt (fd) == -1) { emacs_close (fd); return -1; } if (!(ptyname = ptsname (fd))) { emacs_close (fd); return -1; } snprintf (pty_name, sizeof pty_name, "%s", ptyname); }])
+    AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptsname (int), *ptyname; int grantpt_result; sigset_t blocked; sigemptyset (&blocked); sigaddset (&blocked, SIGCLD); pthread_sigmask (SIG_BLOCK, &blocked, 0); grantpt_result = grantpt (fd); pthread_sigmask (SIG_UNBLOCK, &blocked, 0); if (grantpt_result == -1 || unlockpt (fd) == -1 || !(ptyname = ptsname (fd))) { emacs_close (fd); return -1; } snprintf (pty_name, sizeof pty_name, "%s", ptyname); }])
     ;;
 
   unixware )
     dnl Comments are as per sol2*.
-    AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptsname (int), *ptyname; sigblock(sigmask(SIGCLD)); if (grantpt(fd) == -1) fatal("could not grant slave pty"); sigunblock(sigmask(SIGCLD)); if (unlockpt(fd) == -1) fatal("could not unlock slave pty"); if (!(ptyname = ptsname(fd))) fatal ("could not enable slave pty"); snprintf (pty_name, sizeof pty_name, "%s", ptyname); }])
+    AC_DEFINE(PTY_TTY_NAME_SPRINTF, [{ char *ptsname (int), *ptyname; int grantpt_result; sigset_t blocked; sigemptyset (&blocked); sigaddset (&blocked, SIGCLD); pthread_sigmask (SIG_BLOCK, &blocked, 0); grantpt_result = grantpt (fd); pthread_sigmask (SIG_UNBLOCK, &blocked, 0); if (grantpt_result == -1) fatal("could not grant slave pty"); if (unlockpt(fd) == -1) fatal("could not unlock slave pty"); if (!(ptyname = ptsname(fd))) fatal ("could not enable slave pty"); snprintf (pty_name, sizeof pty_name, "%s", ptyname); }])
     ;;
 esac
 
@@ -3820,13 +3817,6 @@ case $opsys in
     AC_DEFINE(XOS_NEEDS_TIME_H, 1, [Compensate for a bug in Xos.h on
       some systems, where it requires time.h.])
     ;;
-
-  netbsd | openbsd )
-    dnl Greg A. Woods <woods@weird.com> says we must include signal.h
-    dnl before syssignal.h is included, to work around interface conflicts
-    dnl that are handled with CPP __RENAME() macro in signal.h.
-    AC_DEFINE(SIGNAL_H_AHB, 1, [Define if AH_BOTTOM should include signal.h.])
-    ;;
 esac
 
 
diff --git a/src/ChangeLog b/src/ChangeLog
index 479fb38e60b..3bfa9e929d5 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,57 @@
+2012-09-06  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Signal-handler cleanup (Bug#12327).
+        Emacs's signal handlers were written in the old 4.2BSD style with
+        sigblock and sigmask and so forth, and this led to some
+        inefficiencies and confusion.  Rewrite these to use
+        pthread_sigmask etc. without copying signal sets around.  Also,
+        get rid of the confusing macros 'SIGNAL_THREAD_CHECK' and
+        'signal', and instead use functions that do not attempt to take
+        over the system name space.  This patch causes Emacs's text
+        segment to shrink by 0.7% on my platform, Fedora 17 x86-64.
+        * alloc.c, emacsgtkfixed.c, nsfns.m, widget.c, xmenu.c:
+        Do not include <signal.h> or "syssignal.h", as these
+        modules do not use signals.
+        * atimer.c, callproc.c, data.c, dispnew.c, emacs.c, floatfns.c:
+        * gtkutil.c, keyboard.c, process.c, sound.c, sysdep.c, term.c, xterm.c:
+        Do not include <signal.h>, as "syssignal.h" does that for us now.
+        * atimer.c (sigmask_atimers): New function.
+        (block_atimers, unblock_atimers): New functions,
+        replacing the old macros BLOCK_ATIMERS and UNBLOCK_ATIMERS.
+        All uses replaced.
+        * conf_post.h [SIGNAL_H_AHB]: Do not include <signal.h>;
+        no longer needed here.
+        * emacs.c (main): Inspect existing signal handler with sigaction,
+        so that there's no need to block and unblock SIGHUP.
+        * sysdep.c (struct save_signal): New member 'action', replacing
+        old member 'handler'.
+        (save_signal_handlers, restore_signal_handlers):
+        Use sigaction instead of 'signal' to save and restore.
+        (get_set_sighandler, set_sighandler) [!WINDOWSNT]:
+        New function.  All users of 'signal' modified to use set_sighandler
+        if they're writeonly, and to use sys_signal if they're read+write.
+        (emacs_sigaction_init, forwarded_signal): New functions.
+        (sys_signal): Remove.  All uses replaced by calls to sigaction
+        and emacs_sigaction_init, or by direct calls to 'signal'.
+        (sys_sigmask) [!__GNUC__]: Remove; no longer needed.
+        (sys_sigblock, sys_sigunblock, sys_sigsetmask): Remove;
+        all uses replaced by pthread_sigmask etc. calls.
+        * syssignal.h: Include <signal.h>.
+        (emacs_sigaction_init, forwarded_signal): New decls.
+        (SIGMASKTYPE): Remove.  All uses replaced by its definiens, sigset_t.
+        (SIGEMPTYMASK): Remove; all uses replaced by its definiens, empty_mask.
+        (sigmask, sys_sigmask): Remove; no longer needed.
+        (sigpause): Remove.  All uses replaced by its definiens, sigsuspend.
+        (sigblock, sigunblock, sigfree):
+        (sigsetmask) [!defined sigsetmask]:
+        Remove.  All uses replaced by pthread_sigmask.
+        (signal): Remove.  Its remaining uses (with SIG_DFL and SIG_IGN)
+        no longer need to be replaced, and its typical old uses
+        are now done via emacs_sigaction_init and sigaction.
+        (sys_sigblock, sys_sigunblock, sys_sigsetmask): Remove decls.
+        (sys_sigdel): Remove; unused.
+        (NSIG): Remove a FIXME; the code's fine.  Remove an unnecessary ifdef.
+
 2012-09-06  Eli Zaretskii  <eliz@gnu.org>
 
         * process.c (CAN_HANDLE_MULTIPLE_CHILDREN): Fix a typo that broke
@@ -50,7 +104,7 @@
 
 2012-09-05  Paul Eggert  <eggert@cs.ucla.edu>
 
-        Fix race conditions with signal handlers and errno.
+        Fix race conditions with signal handlers and errno (Bug#12327).
         Be more systematic about preserving errno whenever a signal
         handler returns, even if it's not in the main thread.  Do this by
         renaming signal handlers to distinguish between signal delivery
diff --git a/src/alloc.c b/src/alloc.c
index 1a9718bcb25..bf7c156d321 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -26,8 +26,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <limits.h>             /* For CHAR_BIT.  */
 #include <setjmp.h>
 
-#include <signal.h>
-
 #ifdef HAVE_PTHREAD
 #include <pthread.h>
 #endif
@@ -42,7 +40,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "keyboard.h"
 #include "frame.h"
 #include "blockinput.h"
-#include "syssignal.h"
 #include "termhooks.h"          /* For struct terminal.  */
 #include <setjmp.h>
 #include <verify.h>
diff --git a/src/atimer.c b/src/atimer.c
index 060dead9b17..34731920af5 100644
--- a/src/atimer.c
+++ b/src/atimer.c
@@ -17,7 +17,6 @@ You should have received a copy of the GNU General Public License
 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 #include "lisp.h"
@@ -51,8 +50,24 @@ int pending_atimers;
 
 /* Block/unblock SIGALRM.  */
 
-#define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
-#define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
+static void
+sigmask_atimers (int how)
+{
+  sigset_t blocked;
+  sigemptyset (&blocked);
+  sigaddset (&blocked, SIGALRM);
+  pthread_sigmask (how, &blocked, 0);
+}
+static void
+block_atimers (void)
+{
+  sigmask_atimers (SIG_BLOCK);
+}
+static void
+unblock_atimers (void)
+{
+  sigmask_atimers (SIG_UNBLOCK);
+}
 
 /* Function prototypes.  */
 
@@ -109,7 +124,7 @@ start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
   t->fn = fn;
   t->client_data = client_data;
 
-  BLOCK_ATIMERS;
+  block_atimers ();
 
   /* Compute the timer's expiration time.  */
   switch (type)
@@ -130,7 +145,7 @@ start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
 
   /* Insert the timer in the list of active atimers.  */
   schedule_atimer (t);
-  UNBLOCK_ATIMERS;
+  unblock_atimers ();
 
   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
   set_alarm ();
@@ -146,7 +161,7 @@ cancel_atimer (struct atimer *timer)
 {
   int i;
 
-  BLOCK_ATIMERS;
+  block_atimers ();
 
   for (i = 0; i < 2; ++i)
     {
@@ -173,7 +188,7 @@ cancel_atimer (struct atimer *timer)
         }
     }
 
-  UNBLOCK_ATIMERS;
+  unblock_atimers ();
 }
 
 
@@ -204,7 +219,7 @@ append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 void
 stop_other_atimers (struct atimer *t)
 {
-  BLOCK_ATIMERS;
+  block_atimers ();
 
   if (t)
     {
@@ -229,7 +244,7 @@ stop_other_atimers (struct atimer *t)
 
   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
   atimers = t;
-  UNBLOCK_ATIMERS;
+  unblock_atimers ();
 }
 
 
@@ -244,7 +259,7 @@ run_all_atimers (void)
       struct atimer *t = atimers;
       struct atimer *next;
 
-      BLOCK_ATIMERS;
+      block_atimers ();
       atimers = stopped_atimers;
       stopped_atimers = NULL;
 
@@ -255,7 +270,7 @@ run_all_atimers (void)
           t = next;
         }
 
-      UNBLOCK_ATIMERS;
+      unblock_atimers ();
     }
 }
 
@@ -397,9 +412,9 @@ do_pending_atimers (void)
 {
   if (pending_atimers)
     {
-      BLOCK_ATIMERS;
+      block_atimers ();
       run_timers ();
-      UNBLOCK_ATIMERS;
+      unblock_atimers ();
     }
 }
 
@@ -412,7 +427,9 @@ turn_on_atimers (bool on)
 {
   if (on)
     {
-      signal (SIGALRM, deliver_alarm_signal);
+      struct sigaction action;
+      emacs_sigaction_init (&action, deliver_alarm_signal);
+      sigaction (SIGALRM, &action, 0);
       set_alarm ();
     }
   else
@@ -423,8 +440,10 @@ turn_on_atimers (bool on)
 void
 init_atimer (void)
 {
+  struct sigaction action;
   free_atimers = stopped_atimers = atimers = NULL;
   pending_atimers = 0;
   /* pending_signals is initialized in init_keyboard.*/
-  signal (SIGALRM, deliver_alarm_signal);
+  emacs_sigaction_init (&action, deliver_alarm_signal);
+  sigaction (SIGALRM, &action, 0);
 }
diff --git a/src/callproc.c b/src/callproc.c
index 2e9a8950700..a92959a1559 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -19,7 +19,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #include <config.h>
-#include <signal.h>
 #include <errno.h>
 #include <stdio.h>
 #include <setjmp.h>
@@ -506,9 +505,6 @@ usage: (call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)  */)
 
     if (fd_output >= 0)
       fd1 = fd_output;
-#if 0  /* Some systems don't have sigblock.  */
-    mask = sigblock (sigmask (SIGCHLD));
-#endif
 
     /* Record that we're about to create a synchronous process.  */
     synch_process_alive = 1;
diff --git a/src/conf_post.h b/src/conf_post.h
index cef55863752..1bf40af260b 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -40,11 +40,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #endif
 #endif
 
-#ifdef SIGNAL_H_AHB
-#undef SIGNAL_H_AHB
-#include <signal.h>
-#endif
-
 /* This silences a few compilation warnings on FreeBSD.  */
 #ifdef BSD_SYSTEM_AHB
 #undef BSD_SYSTEM_AHB
diff --git a/src/data.c b/src/data.c
index 6151d815b29..5fbf43e424e 100644
--- a/src/data.c
+++ b/src/data.c
@@ -19,7 +19,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #include <config.h>
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 
@@ -3210,7 +3209,7 @@ syms_of_data (void)
 static _Noreturn void
 handle_arith_signal (int sig)
 {
-  sigsetmask (SIGEMPTYMASK);
+  pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
   xsignal0 (Qarith_error);
 }
 
@@ -3223,6 +3222,7 @@ deliver_arith_signal (int sig)
 void
 init_data (void)
 {
+  struct sigaction action;
   /* Don't do this if just dumping out.
      We don't want to call `signal' in this case
      so that we don't have trouble with dumping
@@ -3231,5 +3231,6 @@ init_data (void)
   if (!initialized)
     return;
 #endif /* CANNOT_DUMP */
-  signal (SIGFPE, deliver_arith_signal);
+  emacs_sigaction_init (&action, deliver_arith_signal);
+  sigaction (SIGFPE, &action, 0);
 }
diff --git a/src/dispnew.c b/src/dispnew.c
index e02b33000d8..85b3254aae3 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -21,7 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define DISPEXTERN_INLINE EXTERN_INLINE
 
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 #include <unistd.h>
@@ -5560,7 +5559,9 @@ handle_window_change_signal (int sig)
   int width, height;
   struct tty_display_info *tty;
 
-  signal (SIGWINCH, deliver_window_change_signal);
+  struct sigaction action;
+  emacs_sigaction_init (&action, deliver_window_change_signal);
+  sigaction (SIGWINCH, &action, 0);
 
   /* The frame size change obviously applies to a single
      termcap-controlled terminal, but we can't decide which.
@@ -6175,7 +6176,11 @@ init_display (void)
 #ifndef CANNOT_DUMP
   if (initialized)
 #endif /* CANNOT_DUMP */
-    signal (SIGWINCH, deliver_window_change_signal);
+    {
+      struct sigaction action;
+      emacs_sigaction_init (&action, deliver_window_change_signal);
+      sigaction (SIGWINCH, &action, 0);
+    }
 #endif /* SIGWINCH */
 
   /* If running as a daemon, no need to initialize any frames/terminal. */
diff --git a/src/emacs.c b/src/emacs.c
index fc92b30af26..ff50f409d5c 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -20,7 +20,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #include <config.h>
-#include <signal.h>
 #include <errno.h>
 #include <stdio.h>
 
@@ -322,7 +321,12 @@ fatal_error_backtrace (int sig, int backtrace_limit)
      going to send is probably blocked, so we have to unblock it if we
      want to really receive it.  */
 #ifndef MSDOS
-  sigunblock (sigmask (fatal_error_code));
+  {
+    sigset_t unblocked;
+    sigemptyset (&unblocked);
+    sigaddset (&unblocked, fatal_error_code);
+    pthread_sigmask (SIG_UNBLOCK, &unblocked, 0);
+  }
 #endif
 
   kill (getpid (), fatal_error_code);
@@ -339,7 +343,10 @@ static void deliver_danger_signal (int);
 static void
 handle_danger_signal (int sig)
 {
-  signal (sig, deliver_danger_signal);
+  struct sigaction action;
+  emacs_sigaction_init (&action, deliver_danger_signal);
+  sigaction (sig, &action, 0);
+
   malloc_warning ("Operating system warns that virtual memory is running low.\n");
 
   /* It might be unsafe to call do_auto_save now.  */
@@ -683,6 +690,7 @@ main (int argc, char **argv)
   char dname_arg2[80];
 #endif
   char *ch_to_dir;
+  struct sigaction fatal_error_action;
 
 #if GC_MARK_STACK
   stack_base = &dummy;
@@ -1103,6 +1111,7 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
     }
 
   init_signals ();
+  emacs_sigaction_init (&fatal_error_action, deliver_fatal_signal);
 
   /* Don't catch SIGHUP if dumping.  */
   if (1
@@ -1111,13 +1120,17 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
 #endif
       )
     {
-      sigblock (sigmask (SIGHUP));
       /* In --batch mode, don't catch SIGHUP if already ignored.
          That makes nohup work.  */
-      if (! noninteractive
-          || signal (SIGHUP, SIG_IGN) != SIG_IGN)
-        signal (SIGHUP, deliver_fatal_signal);
-      sigunblock (sigmask (SIGHUP));
+      bool catch_SIGHUP = !noninteractive;
+      if (!catch_SIGHUP)
+        {
+          struct sigaction old_action;
+          sigaction (SIGHUP, 0, &old_action);
+          catch_SIGHUP = old_action.sa_handler != SIG_IGN;
+        }
+      if (catch_SIGHUP)
+        sigaction (SIGHUP, &fatal_error_action, 0);
     }
 
   if (
@@ -1141,68 +1154,73 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
       add_user_signal (SIGUSR2, "sigusr2");
 #endif
 #ifdef SIGABRT
-      signal (SIGABRT, deliver_fatal_signal);
+      sigaction (SIGABRT, &fatal_error_action, 0);
 #endif
 #ifdef SIGHWE
-      signal (SIGHWE, deliver_fatal_signal);
+      sigaction (SIGHWE, &fatal_error_action, 0);
 #endif
 #ifdef SIGPRE
-      signal (SIGPRE, deliver_fatal_signal);
+      sigaction (SIGPRE, &fatal_error_action, 0);
 #endif
 #ifdef SIGORE
-      signal (SIGORE, deliver_fatal_signal);
+      sigaction (SIGORE, &fatal_error_action, 0);
 #endif
 #ifdef SIGUME
-      signal (SIGUME, deliver_fatal_signal);
+      sigaction (SIGUME, &fatal_error_action, 0);
 #endif
 #ifdef SIGDLK
-      signal (SIGDLK, deliver_fatal_signal);
+      sigaction (SIGDLK, &fatal_error_action, 0);
 #endif
 #ifdef SIGCPULIM
-      signal (SIGCPULIM, deliver_fatal_signal);
+      sigaction (SIGCPULIM, &fatal_error_action, 0);
 #endif
 #ifdef SIGIOT
       /* This is missing on some systems - OS/2, for example.  */
-      signal (SIGIOT, deliver_fatal_signal);
+      sigaction (SIGIOT, &fatal_error_action, 0);
 #endif
 #ifdef SIGEMT
-      signal (SIGEMT, deliver_fatal_signal);
+      sigaction (SIGEMT, &fatal_error_action, 0);
 #endif
-      signal (SIGFPE, deliver_fatal_signal);
+      sigaction (SIGFPE, &fatal_error_action, 0);
 #ifdef SIGBUS
-      signal (SIGBUS, deliver_fatal_signal);
+      sigaction (SIGBUS, &fatal_error_action, 0);
 #endif
-      signal (SIGSEGV, deliver_fatal_signal);
+      sigaction (SIGSEGV, &fatal_error_action, 0);
 #ifdef SIGSYS
-      signal (SIGSYS, deliver_fatal_signal);
+      sigaction (SIGSYS, &fatal_error_action, 0);
 #endif
       /*  May need special treatment on MS-Windows. See
           http://lists.gnu.org/archive/html/emacs-devel/2010-09/msg01062.html
           Please update the doc of kill-emacs, kill-emacs-hook, and
           NEWS if you change this.
       */
-      if (noninteractive) signal (SIGINT, deliver_fatal_signal);
-      signal (SIGTERM, deliver_fatal_signal);
+      if (noninteractive)
+        sigaction (SIGINT, &fatal_error_action, 0);
+      sigaction (SIGTERM, &fatal_error_action, 0);
 #ifdef SIGXCPU
-      signal (SIGXCPU, deliver_fatal_signal);
+      sigaction (SIGXCPU, &fatal_error_action, 0);
 #endif
 #ifdef SIGXFSZ
-      signal (SIGXFSZ, deliver_fatal_signal);
+      sigaction (SIGXFSZ, &fatal_error_action, 0);
 #endif /* SIGXFSZ */
 
 #ifdef SIGDANGER
       /* This just means available memory is getting low.  */
-      signal (SIGDANGER, deliver_danger_signal);
+      {
+        struct sigaction action;
+        emacs_sigaction_init (&action, deliver_danger_signal);
+        sigaction (SIGDANGER, &action, 0);
+      }
 #endif
 
 #ifdef AIX
 /* 20 is SIGCHLD, 21 is SIGTTIN, 22 is SIGTTOU.  */
-      signal (SIGXCPU, deliver_fatal_signal);
-      signal (SIGIOINT, deliver_fatal_signal);
-      signal (SIGGRANT, deliver_fatal_signal);
-      signal (SIGRETRACT, deliver_fatal_signal);
-      signal (SIGSOUND, deliver_fatal_signal);
-      signal (SIGMSG, deliver_fatal_signal);
+      sigaction (SIGXCPU, &fatal_error_action, 0);
+      sigaction (SIGIOINT, &fatal_error_action, 0);
+      sigaction (SIGGRANT, &fatal_error_action, 0);
+      sigaction (SIGRETRACT, &fatal_error_action, 0);
+      sigaction (SIGSOUND, &fatal_error_action, 0);
+      sigaction (SIGMSG, &fatal_error_action, 0);
 #endif /* AIX */
     }
 
diff --git a/src/emacsgtkfixed.c b/src/emacsgtkfixed.c
index 1a62b59b7af..940482654b3 100644
--- a/src/emacsgtkfixed.c
+++ b/src/emacsgtkfixed.c
@@ -21,7 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 
 #include "emacsgtkfixed.h"
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 #include "lisp.h"
diff --git a/src/floatfns.c b/src/floatfns.c
index f59cf58228a..e956dc22353 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -45,7 +45,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  */
 
 #include <config.h>
-#include <signal.h>
 #include <setjmp.h>
 #include "lisp.h"
 #include "syssignal.h"
diff --git a/src/gtkutil.c b/src/gtkutil.c
index 3bce5be9cd0..884574e1062 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -21,7 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #ifdef USE_GTK
 #include <float.h>
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 
@@ -1979,7 +1978,10 @@ xg_get_file_name (FRAME_PTR f,
   /* I really don't know why this is needed, but without this the GLIBC add on
      library linuxthreads hangs when the Gnome file chooser backend creates
      threads.  */
-  sigblock (sigmask (__SIGRTMIN));
+  sigset_t blocked;
+  sigemptyset (&blocked);
+  sigaddset (&blocked, __SIGRTMIN);
+  pthread_sigmask (SIG_BLOCK, &blocked, 0);
 #endif /* HAVE_PTHREAD */
 
 #ifdef HAVE_GTK_FILE_SELECTION_NEW
@@ -2001,7 +2003,7 @@ xg_get_file_name (FRAME_PTR f,
   filesel_done = xg_dialog_run (f, w);
 
 #if defined (HAVE_PTHREAD) && defined (__SIGRTMIN)
-  sigunblock (sigmask (__SIGRTMIN));
+  pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
 #endif
 
   if (filesel_done == GTK_RESPONSE_OK)
@@ -2057,7 +2059,10 @@ xg_get_font (FRAME_PTR f, const char *default_name)
   Lisp_Object font = Qnil;
 
 #if defined (HAVE_PTHREAD) && defined (__SIGRTMIN)
-  sigblock (sigmask (__SIGRTMIN));
+  sigset_t blocked;
+  sigemptyset (&blocked);
+  sigaddset (&blocked, __SIGRTMIN);
+  pthread_sigmask (SIG_BLOCK, &blocked, 0);
 #endif /* HAVE_PTHREAD */
 
   w = gtk_font_chooser_dialog_new
@@ -2086,7 +2091,7 @@ xg_get_font (FRAME_PTR f, const char *default_name)
   done = xg_dialog_run (f, w);
 
 #if defined (HAVE_PTHREAD) && defined (__SIGRTMIN)
-  sigunblock (sigmask (__SIGRTMIN));
+  pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
 #endif
 
   if (done == GTK_RESPONSE_OK)
diff --git a/src/keyboard.c b/src/keyboard.c
index 128f9280911..d26cf35e108 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -21,7 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define KEYBOARD_INLINE EXTERN_INLINE
 
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 #include "lisp.h"
@@ -3680,7 +3679,7 @@ kbd_buffer_store_event_hold (register struct input_event *event,
       if (immediate_quit && NILP (Vinhibit_quit))
         {
           immediate_quit = 0;
-          sigfree ();
+          pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
           QUIT;
         }
     }
@@ -3832,7 +3831,11 @@ kbd_buffer_get_event (KBOARD **kbp,
       unhold_keyboard_input ();
 #ifdef SIGIO
       if (!noninteractive)
-        signal (SIGIO, deliver_input_available_signal);
+        {
+          struct sigaction action;
+          emacs_sigaction_init (&action, deliver_input_available_signal);
+          sigaction (SIGIO, &action, 0);
+        }
 #endif /* SIGIO */
       start_polling ();
     }
@@ -6780,10 +6783,12 @@ gobble_input (int expected)
 #ifdef SIGIO
   if (interrupt_input)
     {
-      SIGMASKTYPE mask;
-      mask = sigblock (sigmask (SIGIO));
+      sigset_t blocked, procmask;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGIO);
+      pthread_sigmask (SIG_BLOCK, &blocked, &procmask);
       read_avail_input (expected);
-      sigsetmask (mask);
+      pthread_sigmask (SIG_SETMASK, &procmask, 0);
     }
   else
 #ifdef POLL_FOR_INPUT
@@ -6792,10 +6797,12 @@ gobble_input (int expected)
      it's always set.  */
   if (!interrupt_input && poll_suppress_count == 0)
     {
-      SIGMASKTYPE mask;
-      mask = sigblock (sigmask (SIGALRM));
+      sigset_t blocked, procmask;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGALRM);
+      pthread_sigmask (SIG_BLOCK, &blocked, &procmask);
       read_avail_input (expected);
-      sigsetmask (mask);
+      pthread_sigmask (SIG_SETMASK, &procmask, 0);
     }
   else
 #endif
@@ -6831,10 +6838,12 @@ record_asynch_buffer_change (void)
 #ifdef SIGIO
   if (interrupt_input)
     {
-      SIGMASKTYPE mask;
-      mask = sigblock (sigmask (SIGIO));
+      sigset_t blocked, procmask;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGIO);
+      pthread_sigmask (SIG_BLOCK, &blocked, &procmask);
       kbd_buffer_store_event (&event);
-      sigsetmask (mask);
+      pthread_sigmask (SIG_SETMASK, &procmask, 0);
     }
   else
 #endif
@@ -7295,6 +7304,7 @@ static struct user_signal_info *user_signals = NULL;
 void
 add_user_signal (int sig, const char *name)
 {
+  struct sigaction action;
   struct user_signal_info *p;
 
   for (p = user_signals; p; p = p->next)
@@ -7309,7 +7319,8 @@ add_user_signal (int sig, const char *name)
   p->next = user_signals;
   user_signals = p;
 
-  signal (sig, deliver_user_signal);
+  emacs_sigaction_init (&action, deliver_user_signal);
+  sigaction (sig, &action, 0);
 }
 
 static void
@@ -7381,7 +7392,7 @@ store_user_signal_events (void)
   for (p = user_signals; p; p = p->next)
     if (p->npending > 0)
       {
-        SIGMASKTYPE mask;
+        sigset_t blocked, procmask;
 
         if (nstored == 0)
           {
@@ -7391,7 +7402,10 @@ store_user_signal_events (void)
           }
         nstored += p->npending;
 
-        mask = sigblock (sigmask (p->sig));
+        sigemptyset (&blocked);
+        sigaddset (&blocked, p->sig);
+        pthread_sigmask (SIG_BLOCK, &blocked, &procmask);
+
         do
           {
             buf.code = p->sig;
@@ -7399,7 +7413,8 @@ store_user_signal_events (void)
             p->npending--;
           }
         while (p->npending > 0);
-        sigsetmask (mask);
+
+        pthread_sigmask (SIG_SETMASK, &procmask, 0);
       }
 
   return nstored;
@@ -10838,7 +10853,10 @@ handle_interrupt (void)
       /* If SIGINT isn't blocked, don't let us be interrupted by
          another SIGINT, it might be harmful due to non-reentrancy
          in I/O functions.  */
-      sigblock (sigmask (SIGINT));
+      sigset_t blocked;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGINT);
+      pthread_sigmask (SIG_BLOCK, &blocked, 0);
 
       fflush (stdout);
       reset_all_sys_modes ();
@@ -10909,7 +10927,7 @@ handle_interrupt (void)
 #endif /* not MSDOS */
       fflush (stdout);
       init_all_sys_modes ();
-      sigfree ();
+      pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
     }
   else
     {
@@ -10922,7 +10940,7 @@ handle_interrupt (void)
           struct gcpro gcpro1, gcpro2, gcpro3, gcpro4;
 
           immediate_quit = 0;
-          sigfree ();
+          pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
           saved = gl_state;
           GCPRO4 (saved.object, saved.global_code,
                   saved.current_syntax_table, saved.old_prop);
@@ -10967,7 +10985,7 @@ quit_throw_to_read_char (int from_signal)
   if (!from_signal && EQ (Vquit_flag, Qkill_emacs))
     Fkill_emacs (Qnil);
 
-  sigfree ();
+  pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
   /* Prevent another signal from doing this before we finish.  */
   clear_waiting_for_input ();
   input_pending = 0;
@@ -11402,17 +11420,23 @@ init_keyboard (void)
          SIGINT.  There is special code in interrupt_signal to exit
          Emacs on SIGINT when there are no termcap frames on the
          controlling terminal.  */
-      signal (SIGINT, deliver_interrupt_signal);
+      struct sigaction action;
+      emacs_sigaction_init (&action, deliver_interrupt_signal);
+      sigaction (SIGINT, &action, 0);
 #ifndef DOS_NT
       /* For systems with SysV TERMIO, C-g is set up for both SIGINT and
          SIGQUIT and we can't tell which one it will give us.  */
-      signal (SIGQUIT, deliver_interrupt_signal);
+      sigaction (SIGQUIT, &action, 0);
 #endif /* not DOS_NT */
     }
 /* Note SIGIO has been undef'd if FIONREAD is missing.  */
 #ifdef SIGIO
   if (!noninteractive)
-    signal (SIGIO, deliver_input_available_signal);
+    {
+      struct sigaction action;
+      emacs_sigaction_init (&action, deliver_input_available_signal);
+      sigaction (SIGIO, &action, 0);
+    }
 #endif /* SIGIO */
 
 /* Use interrupt input by default, if it works and noninterrupt input
@@ -11424,7 +11448,7 @@ init_keyboard (void)
   interrupt_input = 0;
 #endif
 
-  sigfree ();
+  pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
   dribble = 0;
 
   if (keyboard_init_hook)
diff --git a/src/nsfns.m b/src/nsfns.m
index e8b5d22077a..f73086eeee9 100644
--- a/src/nsfns.m
+++ b/src/nsfns.m
@@ -30,7 +30,6 @@ GNUstep port and post-20 update by Adrian Robert (arobert@cogsci.ucsd.edu)
    interpretation of even the system includes. */
 #include <config.h>
 
-#include <signal.h>
 #include <math.h>
 #include <setjmp.h>
 #include <c-strcase.h>
diff --git a/src/process.c b/src/process.c
index 9ab8d2720b2..0cc9bc353a1 100644
--- a/src/process.c
+++ b/src/process.c
@@ -23,7 +23,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define PROCESS_INLINE EXTERN_INLINE
 
-#include <signal.h>
 #include <stdio.h>
 #include <errno.h>
 #include <setjmp.h>
@@ -1612,8 +1611,7 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
 #if !defined (WINDOWSNT) && defined (FD_CLOEXEC)
   int wait_child_setup[2];
 #endif
-  sigset_t procmask;
-  sigset_t blocked;
+  sigset_t blocked, procmask;
   struct sigaction sigint_action;
   struct sigaction sigquit_action;
   struct sigaction sigpipe_action;
@@ -1765,12 +1763,6 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
         int xforkin = forkin;
         int xforkout = forkout;
 
-#if 0 /* This was probably a mistake--it duplicates code later on,
-         but fails to handle all the cases.  */
-        /* Make sure SIGCHLD is not blocked in the child.  */
-        sigsetmask (SIGEMPTYMASK);
-#endif
-
         /* Make the pty be the controlling terminal of the process.  */
 #ifdef HAVE_PTYS
         /* First, disconnect its current controlling terminal.  */
@@ -5434,7 +5426,10 @@ static Lisp_Object process_sent_to;
 static _Noreturn void
 handle_pipe_signal (int sig)
 {
-  sigunblock (sigmask (SIGPIPE));
+  sigset_t unblocked;
+  sigemptyset (&unblocked);
+  sigaddset (&unblocked, SIGPIPE);
+  pthread_sigmask (SIG_UNBLOCK, &unblocked, 0);
   _longjmp (send_process_frame, 1);
 }
 
@@ -5534,7 +5529,7 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
   struct Lisp_Process *p = XPROCESS (proc);
   ssize_t rv;
   struct coding_system *coding;
-  void (*volatile old_sigpipe) (int);
+  struct sigaction old_sigpipe_action;
 
   if (p->raw_status_new)
     update_status (p);
@@ -5673,7 +5668,9 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
               /* Send this batch, using one or more write calls.  */
               ptrdiff_t written = 0;
               int outfd = p->outfd;
-              old_sigpipe = signal (SIGPIPE, deliver_pipe_signal);
+              struct sigaction action;
+              emacs_sigaction_init (&action, deliver_pipe_signal);
+              sigaction (SIGPIPE, &action, &old_sigpipe_action);
 #ifdef DATAGRAM_SOCKETS
               if (DATAGRAM_CHAN_P (outfd))
                 {
@@ -5684,7 +5681,7 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
                     written = rv;
                   else if (errno == EMSGSIZE)
                     {
-                      signal (SIGPIPE, old_sigpipe);
+                      sigaction (SIGPIPE, &old_sigpipe_action, 0);
                       report_file_error ("sending datagram",
                                          Fcons (proc, Qnil));
                     }
@@ -5709,7 +5706,7 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
                     }
 #endif
                 }
-              signal (SIGPIPE, old_sigpipe);
+              sigaction (SIGPIPE, &old_sigpipe_action, 0);
 
               if (rv < 0)
                 {
@@ -5769,7 +5766,7 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
     }
   else
     {
-      signal (SIGPIPE, old_sigpipe);
+      sigaction (SIGPIPE, &old_sigpipe_action, 0);
       proc = process_sent_to;
       p = XPROCESS (proc);
       p->raw_status_new = 0;
@@ -7389,7 +7386,11 @@ init_process_emacs (void)
 #ifndef CANNOT_DUMP
   if (! noninteractive || initialized)
 #endif
-    signal (SIGCHLD, deliver_child_signal);
+    {
+      struct sigaction action;
+      emacs_sigaction_init (&action, deliver_child_signal);
+      sigaction (SIGCHLD, &action, 0);
+    }
 #endif
 
   FD_ZERO (&input_wait_mask);
diff --git a/src/sound.c b/src/sound.c
index d20fa5ee8eb..5729d704b6a 100644
--- a/src/sound.c
+++ b/src/sound.c
@@ -48,7 +48,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "lisp.h"
 #include "dispextern.h"
 #include "atimer.h"
-#include <signal.h>
 #include "syssignal.h"
 /* END: Common Includes */
 
@@ -316,7 +315,12 @@ sound_perror (const char *msg)
 
   turn_on_atimers (1);
 #ifdef SIGIO
-  sigunblock (sigmask (SIGIO));
+  {
+    sigset_t unblocked;
+    sigemptyset (&unblocked);
+    sigaddset (&unblocked, SIGIO);
+    pthread_sigmask (SIG_UNBLOCK, &unblocked, 0);
+  }
 #endif
   if (saved_errno != 0)
     error ("%s: %s", msg, strerror (saved_errno));
@@ -728,6 +732,9 @@ static void
 vox_configure (struct sound_device *sd)
 {
   int val;
+#ifdef SIGIO
+  sigset_t blocked;
+#endif
 
   eassert (sd->fd >= 0);
 
@@ -736,7 +743,9 @@ vox_configure (struct sound_device *sd)
      troubles.  */
   turn_on_atimers (0);
 #ifdef SIGIO
-  sigblock (sigmask (SIGIO));
+  sigemptyset (&blocked);
+  sigaddset (&blocked, SIGIO);
+  pthread_sigmask (SIG_BLOCK, &blocked, 0);
 #endif
 
   val = sd->format;
@@ -770,7 +779,7 @@ vox_configure (struct sound_device *sd)
 
   turn_on_atimers (1);
 #ifdef SIGIO
-  sigunblock (sigmask (SIGIO));
+  pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
 #endif
 }
 
@@ -786,7 +795,10 @@ vox_close (struct sound_device *sd)
          be interrupted by a signal.  Block the ones we know to cause
          troubles.  */
 #ifdef SIGIO
-      sigblock (sigmask (SIGIO));
+      sigset_t blocked;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGIO);
+      pthread_sigmask (SIG_BLOCK, &blocked, 0);
 #endif
       turn_on_atimers (0);
 
@@ -795,7 +807,7 @@ vox_close (struct sound_device *sd)
 
       turn_on_atimers (1);
 #ifdef SIGIO
-      sigunblock (sigmask (SIGIO));
+      pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
 #endif
 
       /* Close the device.  */
diff --git a/src/sysdep.c b/src/sysdep.c
index 42b8baf78e0..0f16d1a7645 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -22,7 +22,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define SYSTIME_INLINE EXTERN_INLINE
 
 #include <execinfo.h>
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 #ifdef HAVE_PWD_H
@@ -303,27 +302,34 @@ wait_for_termination_1 (pid_t pid, int interruptible)
          termination of subprocesses, perhaps involving a kernel bug too,
          but no idea what it is.  Just as a hunch we signal SIGCHLD to see
          if that causes the problem to go away or get worse.  */
-      sigsetmask (sigmask (SIGCHLD));
+      sigset_t sigchild_mask;
+      sigemptyset (&sigchild_mask);
+      sigaddset (&sigchild_mask, SIGCHLD);
+      pthread_sigmask (SIG_SETMASK, &sigchild_mask, 0);
+
       if (0 > kill (pid, 0))
         {
-          sigsetmask (SIGEMPTYMASK);
+          pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
           kill (getpid (), SIGCHLD);
           break;
         }
       if (wait_debugging)
         sleep (1);
       else
-        sigpause (SIGEMPTYMASK);
+        sigsuspend (&empty_mask);
 #else /* not BSD_SYSTEM, and not HPUX version >= 6 */
 #ifdef WINDOWSNT
       wait (0);
       break;
 #else /* not WINDOWSNT */
-      sigblock (sigmask (SIGCHLD));
+      sigset_t blocked;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGCHLD);
+      pthread_sigmask (SIG_BLOCK, &blocked, 0);
       errno = 0;
       if (kill (pid, 0) == -1 && errno == ESRCH)
         {
-          sigunblock (sigmask (SIGCHLD));
+          pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
           break;
         }
 
@@ -457,11 +463,11 @@ child_setup_tty (int out)
 #endif  /* not MSDOS */
 
 
-/* Record a signal code and the handler for it.  */
+/* Record a signal code and the action for it.  */
 struct save_signal
 {
   int code;
-  void (*handler) (int);
+  struct sigaction action;
 };
 
 static void save_signal_handlers (struct save_signal *);
@@ -619,8 +625,9 @@ save_signal_handlers (struct save_signal *saved_handlers)
 {
   while (saved_handlers->code)
     {
-      saved_handlers->handler
-        = (void (*) (int)) signal (saved_handlers->code, SIG_IGN);
+      struct sigaction action;
+      emacs_sigaction_init (&action, SIG_IGN);
+      sigaction (saved_handlers->code, &action, &saved_handlers->action);
       saved_handlers++;
     }
 }
@@ -630,7 +637,7 @@ restore_signal_handlers (struct save_signal *saved_handlers)
 {
   while (saved_handlers->code)
     {
-      signal (saved_handlers->code, saved_handlers->handler);
+      sigaction (saved_handlers->code, &saved_handlers->action, 0);
       saved_handlers++;
     }
 }
@@ -687,13 +694,17 @@ reset_sigio (int fd)
 void
 request_sigio (void)
 {
+  sigset_t unblocked;
+
   if (noninteractive)
     return;
 
+  sigemptyset (&unblocked);
 #ifdef SIGWINCH
-  sigunblock (sigmask (SIGWINCH));
+  sigaddset (&unblocked, SIGWINCH);
 #endif
-  sigunblock (sigmask (SIGIO));
+  sigaddset (&unblocked, SIGIO);
+  pthread_sigmask (SIG_UNBLOCK, &unblocked, 0);
 
   interrupts_deferred = 0;
 }
@@ -701,6 +712,8 @@ request_sigio (void)
 void
 unrequest_sigio (void)
 {
+  sigset_t blocked;
+
   if (noninteractive)
     return;
 
@@ -709,10 +722,12 @@ unrequest_sigio (void)
     return;
 #endif
 
+  sigemptyset (&blocked);
 #ifdef SIGWINCH
-  sigblock (sigmask (SIGWINCH));
+  sigaddset (&blocked, SIGWINCH);
 #endif
-  sigblock (sigmask (SIGIO));
+  sigaddset (&blocked, SIGIO);
+  pthread_sigmask (SIG_BLOCK, &blocked, 0);
   interrupts_deferred = 1;
 }
 
@@ -1471,20 +1486,16 @@ init_system_name (void)
   }
 }
 
-/* POSIX signals support - DJB */
-/* Anyone with POSIX signals should have ANSI C declarations */
-
 sigset_t empty_mask;
 
-#ifndef WINDOWSNT
-
-signal_handler_t
-sys_signal (int signal_number, signal_handler_t action)
+/* Store into *ACTION a signal action suitable for Emacs, with handler
+   HANDLER.  */
+void
+emacs_sigaction_init (struct sigaction *action, signal_handler_t handler)
 {
-  struct sigaction new_action, old_action;
-  sigemptyset (&new_action.sa_mask);
-  new_action.sa_handler = action;
-  new_action.sa_flags = 0;
+  sigemptyset (&action->sa_mask);
+  action->sa_handler = handler;
+  action->sa_flags = 0;
 #if defined (SA_RESTART)
   /* Emacs mostly works better with restartable system services. If this
      flag exists, we probably want to turn it on here.
@@ -1501,54 +1512,8 @@ sys_signal (int signal_number, signal_handler_t action)
 # if defined (BROKEN_SA_RESTART) || defined (SYNC_INPUT)
   if (noninteractive)
 # endif
-    new_action.sa_flags = SA_RESTART;
+    action->sa_flags = SA_RESTART;
 #endif
-  sigaction (signal_number, &new_action, &old_action);
-  return (old_action.sa_handler);
-}
-
-#endif  /* WINDOWSNT */
-
-#ifndef __GNUC__
-/* If we're compiling with GCC, we don't need this function, since it
-   can be written as a macro.  */
-sigset_t
-sys_sigmask (int sig)
-{
-  sigset_t mask;
-  sigemptyset (&mask);
-  sigaddset (&mask, sig);
-  return mask;
-}
-#endif
-
-/* I'd like to have these guys return pointers to the mask storage in here,
-   but there'd be trouble if the code was saving multiple masks.  I'll be
-   safe and pass the structure.  It normally won't be more than 2 bytes
-   anyhow. - DJB */
-
-sigset_t
-sys_sigblock (sigset_t new_mask)
-{
-  sigset_t old_mask;
-  pthread_sigmask (SIG_BLOCK, &new_mask, &old_mask);
-  return (old_mask);
-}
-
-sigset_t
-sys_sigunblock (sigset_t new_mask)
-{
-  sigset_t old_mask;
-  pthread_sigmask (SIG_UNBLOCK, &new_mask, &old_mask);
-  return (old_mask);
-}
-
-sigset_t
-sys_sigsetmask (sigset_t new_mask)
-{
-  sigset_t old_mask;
-  pthread_sigmask (SIG_SETMASK, &new_mask, &old_mask);
-  return (old_mask);
 }
 
 #ifdef FORWARD_SIGNAL_TO_MAIN_THREAD
diff --git a/src/syssignal.h b/src/syssignal.h
index 504aff43083..58290ee3fc7 100644
--- a/src/syssignal.h
+++ b/src/syssignal.h
@@ -17,6 +17,8 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include <signal.h>
+
 extern void init_signals (void);
 
 #ifdef HAVE_PTHREAD
@@ -26,63 +28,16 @@ extern void init_signals (void);
 #define FORWARD_SIGNAL_TO_MAIN_THREAD
 #endif
 
-/* Don't #include <signal.h>.  That header should always be #included
-   before "config.h", because some configuration files (like s/hpux.h)
-   indicate that SIGIO doesn't work by #undef-ing SIGIO.  If this file
-   #includes <signal.h>, then that will re-#define SIGIO and confuse
-   things.  */
-/* XXX This is not correct anymore, there is a BROKEN_SIGIO macro. */
-
-#define SIGMASKTYPE sigset_t
-
-#define SIGEMPTYMASK (empty_mask)
 extern sigset_t empty_mask;
 
-/* POSIX pretty much destroys any possibility of writing sigmask as a
-   macro in standard C.  We always define our own version because the
-   predefined macro in Glibc 2.1 is only provided for compatibility for old
-   programs that use int as signal mask type.  */
-#undef sigmask
-#ifdef __GNUC__
-#define sigmask(SIG)                            \
-  ({                                            \
-    sigset_t _mask;                             \
-    sigemptyset (&_mask);                       \
-    sigaddset (&_mask, SIG);                    \
-    _mask;                                      \
-  })
-#else /* ! defined (__GNUC__) */
-extern sigset_t sys_sigmask ();
-#define sigmask(SIG) (sys_sigmask (SIG))
-#endif /* ! defined (__GNUC__) */
-
-#undef sigpause
-#define sigpause(MASK)    sigsuspend (&(MASK))
-
-#define sigblock(SIG)    sys_sigblock (SIG)
-#define sigunblock(SIG)  sys_sigunblock (SIG)
-#ifndef sigsetmask
-#define sigsetmask(SIG)  sys_sigsetmask (SIG)
-#endif
-#undef signal
-#define signal(SIG,ACT)      sys_signal(SIG,ACT)
-
-/* Whether this is what all systems want or not, this is what
-   appears to be assumed in the source, for example data.c:arith_error.  */
 typedef void (*signal_handler_t) (int);
 
-signal_handler_t sys_signal (int signal_number, signal_handler_t action);
-sigset_t sys_sigblock   (sigset_t new_mask);
-sigset_t sys_sigunblock (sigset_t new_mask);
-sigset_t sys_sigsetmask (sigset_t new_mask);
+extern void emacs_sigaction_init (struct sigaction *, signal_handler_t);
+
 #if ! (defined TIOCNOTTY || defined USG5 || defined CYGWIN)
 _Noreturn void croak (char *);
 #endif
 
-#define sys_sigdel(MASK,SIG) sigdelset (&MASK,SIG)
-
-#define sigfree() sigsetmask (SIGEMPTYMASK)
-
 #if defined (SIGIO) && defined (BROKEN_SIGIO)
 # undef SIGIO
 #endif
@@ -97,12 +52,8 @@ _Noreturn void croak (char *);
 #undef SIGPTY
 #endif
 
-
-/* FIXME?  Emacs only defines NSIG_MINIMUM on some platforms?  */
 #if NSIG < NSIG_MINIMUM
-# ifdef NSIG
-#  undef NSIG
-# endif
+# undef NSIG
 # define NSIG NSIG_MINIMUM
 #endif
 
diff --git a/src/term.c b/src/term.c
index 8cc5dfd2a87..0eaf76a13df 100644
--- a/src/term.c
+++ b/src/term.c
@@ -25,7 +25,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <sys/file.h>
 #include <sys/time.h>
 #include <unistd.h>
-#include <signal.h>
 #include <setjmp.h>
 
 #include "lisp.h"
@@ -2932,7 +2931,10 @@ dissociate_if_controlling_tty (int fd)
       no_controlling_tty = 1;
 #else
 #ifdef TIOCNOTTY                /* Try BSD ioctls. */
-      sigblock (sigmask (SIGTTOU));
+      sigset_t blocked;
+      sigemptyset (&blocked);
+      sigaddset (&blocked, SIGTTOU);
+      pthread_sigmask (SIG_BLOCK, &blocked, 0);
       fd = emacs_open (DEV_TTY, O_RDWR, 0);
       if (fd != -1 && ioctl (fd, TIOCNOTTY, 0) != -1)
         {
@@ -2940,7 +2942,7 @@ dissociate_if_controlling_tty (int fd)
         }
       if (fd != -1)
         emacs_close (fd);
-      sigunblock (sigmask (SIGTTOU));
+      pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
 #else
       /* Unknown system. */
       croak ();
@@ -3074,9 +3076,14 @@ init_tty (const char *name, const char *terminal_type, int must_succeed)
 
   /* On some systems, tgetent tries to access the controlling
      terminal. */
-  sigblock (sigmask (SIGTTOU));
-  status = tgetent (tty->termcap_term_buffer, terminal_type);
-  sigunblock (sigmask (SIGTTOU));
+  {
+    sigset_t blocked;
+    sigemptyset (&blocked);
+    sigaddset (&blocked, SIGTTOU);
+    pthread_sigmask (SIG_BLOCK, &blocked, 0);
+    status = tgetent (tty->termcap_term_buffer, terminal_type);
+    pthread_sigmask (SIG_UNBLOCK, &blocked, 0);
+  }
 
   if (status < 0)
     {
diff --git a/src/widget.c b/src/widget.c
index 9eaf6d1df6a..0100acc8143 100644
--- a/src/widget.c
+++ b/src/widget.c
@@ -50,9 +50,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <X11/ShellP.h>
 #include "../lwlib/lwlib.h"
 
-#include <signal.h>
-#include "syssignal.h"
-
 #include "character.h"
 #include "font.h"
 
diff --git a/src/xmenu.c b/src/xmenu.c
index 6f92da1b814..605db13e149 100644
--- a/src/xmenu.c
+++ b/src/xmenu.c
@@ -32,11 +32,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 
-#if 0  /* Why was this included?  And without syssignal.h?  */
-/* On 4.3 this loses if it comes after xterm.h.  */
-#include <signal.h>
-#endif
-
 #include <stdio.h>
 #include <setjmp.h>
 
diff --git a/src/xterm.c b/src/xterm.c
index 047b5569bf4..f0f6702cd67 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -21,7 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Xt features made by Fred Pierresteguy.  */
 
 #include <config.h>
-#include <signal.h>
 #include <stdio.h>
 #include <setjmp.h>
 
@@ -29,9 +28,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "lisp.h"
 #include "blockinput.h"
-
-/* Need syssignal.h for various externs and definitions that may be required
-   by some configurations for calls to signal later in this source file.  */
 #include "syssignal.h"
 
 /* This may include sys/types.h, and that somehow loses
@@ -7766,7 +7762,9 @@ x_connection_signal (int signalnum)	/* If we don't have an argument, */
 #ifdef USG
   /* USG systems forget handlers when they are used;
      must reestablish each time */
-  signal (signalnum, x_connection_signal);
+  struct sigaction action;
+  emacs_sigaction_init (&action, x_connection_signal);
+  sigaction (signalnum, &action, 0);
 #endif /* USG */
 }
 
@@ -7876,10 +7874,15 @@ For details, see etc/PROBLEMS.\n",
     }
 
   /* Ordinary stack unwind doesn't deal with these.  */
+  {
+    sigset_t unblocked;
+    sigemptyset (&unblocked);
 #ifdef SIGIO
-  sigunblock (sigmask (SIGIO));
+    sigaddset (&unblocked, SIGIO);
 #endif
-  sigunblock (sigmask (SIGALRM));
+    sigaddset (&unblocked, SIGALRM);
+    pthread_sigmask (SIG_UNBLOCK, &unblocked, 0);
+  }
   TOTALLY_UNBLOCK_INPUT;
 
   unbind_to (idx, Qnil);
@@ -10759,6 +10762,8 @@ x_create_terminal (struct x_display_info *dpyinfo)
 void
 x_initialize (void)
 {
+  struct sigaction action;
+
   baud_rate = 19200;
 
   x_noop_count = 0;
@@ -10805,7 +10810,8 @@ x_initialize (void)
   XSetErrorHandler (x_error_handler);
   XSetIOErrorHandler (x_io_error_quitter);
 
-  signal (SIGPIPE, x_connection_signal);
+  emacs_sigaction_init (&action, x_connection_signal);
+  sigaction (SIGPIPE, &action, 0);
 }