Handle sigmask better with nested signal handlers.

* atimer.c (sigmask_atimers): Remove.
Remaining use rewritten to use body of this function.
* atimer.c (block_atimers, unblock_atimers):
* callproc.c (block_child_signal, unblock_child_signal):
* sysdep.c (block_tty_out_signal, unblock_tty_out_signal):
New arg OLDSET.  All callers changed.
* atimer.c (block_atimers, unblock_atimers):
* callproc.c (block_child_signal, unblock_child_signal):
* keyboard.c (handle_interrupt):
* sound.c (vox_configure, vox_close):
Restore the old signal mask rather than unilaterally clearing bits
from the mask, in case a handler is running within another
handler.  All callers changed.
* lisp.h, process.c, process.h, term.c:
Adjust decls and callers to match new API.
* sysdep.c (emacs_sigaction_init): Don't worry about masking SIGFPE;
signal handlers aren't supposed to use floating point anyway.
(handle_arith_signal): Unblock just SIGFPE rather than clearing mask.

Fixes: debbugs:15561

1 files changed, 6 insertions, 4 deletions

diff --git a/src/term.c b/src/term.c
index 3bcbb70aff6..df5fc17a0c0 100644
--- a/src/term.c
+++ b/src/term.c
@@ -3944,9 +3944,10 @@ dissociate_if_controlling_tty (int fd)
       /* setsid failed, presumably because Emacs is already a process
          group leader.  Fall back on the obsolescent way to dissociate
          a controlling tty.  */
-      block_tty_out_signal ();
+      sigset_t oldset;
+      block_tty_out_signal (&oldset);
       ioctl (fd, TIOCNOTTY, 0);
-      unblock_tty_out_signal ();
+      unblock_tty_out_signal (&oldset);
 #endif
     }
 }
@@ -3970,6 +3971,7 @@ init_tty (const char *name, const char *terminal_type, bool must_succeed)
   int status;
   struct tty_display_info *tty = NULL;
   struct terminal *terminal = NULL;
+  sigset_t oldset;
   bool ctty = false;  /* True if asked to open controlling tty.  */
 
   if (!terminal_type)
@@ -4059,11 +4061,11 @@ init_tty (const char *name, const char *terminal_type, bool must_succeed)
 
   /* On some systems, tgetent tries to access the controlling
      terminal.  */
-  block_tty_out_signal ();
+  block_tty_out_signal (&oldset);
   status = tgetent (tty->termcap_term_buffer, terminal_type);
   if (tty->termcap_term_buffer[TERMCAP_BUFFER_SIZE - 1])
     emacs_abort ();
-  unblock_tty_out_signal ();
+  unblock_tty_out_signal (&oldset);
 
   if (status < 0)
     {