Mercurial > hg > octave-lojdl > gnulib-hg
changeset 4786:83d8d561903a
Improved 'fatal-signal' module.
| author | Bruno Haible <bruno@clisp.org> |
|---|---|
| date | Tue, 14 Oct 2003 12:09:12 +0000 |
| parents | c64759561528 |
| children | 70c4b1691efd |
| files | ChangeLog lib/ChangeLog lib/fatal-signal.c lib/fatal-signal.h m4/ChangeLog m4/fatal-signal.m4 modules/fatal-signal |
| diffstat | 7 files changed, 72 insertions(+), 14 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,7 @@ +2003-10-14 Bruno Haible <bruno@clisp.org> + + * modules/fatal-signal: Add m4/sig_atomic_t.m4 to file list. + 2003-10-12 Paul Eggert <eggert@twinsun.com> * modules/xalloc: Do not depend on 'exit'. Depend on 'stdbool'.
--- a/lib/ChangeLog +++ b/lib/ChangeLog @@ -1,3 +1,9 @@ +2003-10-14 Bruno Haible <bruno@clisp.org> + + * fatal-signal.h: Improved comments. Suggested by Paul Eggert. + * fatal-signal.c: Use sig_atomic_t. Suggested by Paul Eggert. + Also use volatile where needed. + 2003-10-12 Paul Eggert <eggert@twinsun.com> * lib/xalloc.h (xnmalloc, xzalloc, xnrealloc, xclone): New decls.
--- a/lib/fatal-signal.c +++ b/lib/fatal-signal.c @@ -50,6 +50,7 @@ SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS, SIGSYS - because it is more similar to SIGABRT, SIGSEGV, SIGPWR - because it of too special use, + SIGRTMIN...SIGRTMAX - because they are reserved for application use. plus SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */ @@ -85,11 +86,21 @@ /* ========================================================================= */ +typedef void (*action_t) (void); + +/* Type of an entry in the actions array. + The 'action' field is accessed from within the fatal_signal_handler(), + therefore we mark it as 'volatile'. */ +typedef struct +{ + volatile action_t action; +} +actions_entry_t; + /* The registered cleanup actions. */ -typedef void (*action_t) (void); -static action_t static_actions[32]; -static action_t * volatile actions = static_actions; -static size_t volatile actions_count = 0; +static actions_entry_t static_actions[32]; +static actions_entry_t * volatile actions = static_actions; +static sig_atomic_t volatile actions_count = 0; static size_t actions_allocated = SIZEOF (static_actions); @@ -117,12 +128,15 @@ break; n--; actions_count = n; - action = actions[n]; + action = actions[n].action; /* Execute the action. */ action (); } - /* Now execute the signal's default action. */ + /* Now execute the signal's default action. + If signal() blocks the signal being delivered for the duration of the + signal handler's execution, the re-raised signal is delivered when this + handler returns; otherwise it is delivered already during raise(). */ uninstall_handlers (); #if HAVE_RAISE raise (sig); @@ -160,19 +174,24 @@ /* Extend the actions array. Note that we cannot use xrealloc(), because then the cleanup() function could access an already deallocated array. */ - action_t *old_actions = actions; + actions_entry_t *old_actions = actions; size_t new_actions_allocated = 2 * actions_allocated; - action_t *new_actions = - xmalloc (new_actions_allocated * sizeof (action_t)); + actions_entry_t *new_actions = + xmalloc (new_actions_allocated * sizeof (actions_entry_t)); - memcpy (new_actions, actions, actions_allocated * sizeof (action_t)); + memcpy (new_actions, old_actions, + actions_allocated * sizeof (actions_entry_t)); actions = new_actions; actions_allocated = new_actions_allocated; /* Now we can free the old actions array. */ if (old_actions != static_actions) free (old_actions); } - actions[actions_count] = action; + /* The two uses of 'volatile' in the types above (and ISO C 99 section + 5.1.2.3.(5)) ensure that we increment the actions_count only after + the new action has been written to the memory location + actions[actions_count]. */ + actions[actions_count].action = action; actions_count++; } @@ -200,6 +219,7 @@ } } +/* Temporarily delay the catchable fatal signals. */ void block_fatal_signals () { @@ -207,6 +227,7 @@ sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL); } +/* Stop delaying the catchable fatal signals. */ void unblock_fatal_signals () {
--- a/lib/fatal-signal.h +++ b/lib/fatal-signal.h @@ -29,7 +29,24 @@ The limitation of this facility is that it cannot work for SIGKILL. */ /* Register a cleanup function to be executed when a catchable fatal signal - occurs. */ + occurs. + + Restrictions for the cleanup function: + - The cleanup function can do all kinds of system calls. + - It can also access application dependent memory locations and data + structures provided they are in a consistent state. One way to ensure + this is through block_fatal_signals()/unblock_fatal_signals(), see + below. Another - more tricky - way to ensure this is the careful use + of 'volatile'. + However, + - malloc() and similarly complex facilities are not safe to be called + because they are not guaranteed to be in a consistent state. + - Also, the cleanup function must not block the catchable fatal signals + and leave them blocked upon return. + + The cleanup function is executed asynchronously. It is unspecified + whether during its execution the catchable fatal signals are blocked + or not. */ extern void at_fatal_signal (void (*function) (void)); @@ -40,7 +57,10 @@ functions create the temporary file or directory _before_ returning its name to the application. */ -/* Temporarily delay the catchable fatal signals. */ +/* Temporarily delay the catchable fatal signals. + The signals will be blocked (= delayed) until the next call to + unblock_fatal_signals(). If the signals are already blocked, a further + call to block_fatal_signals() has no effect. */ extern void block_fatal_signals (void); /* Stop delaying the catchable fatal signals. */
--- a/m4/ChangeLog +++ b/m4/ChangeLog @@ -1,3 +1,8 @@ +2003-10-14 Bruno Haible <bruno@clisp.org> + + * sig_atomic_t: New file, from GNU gettext. + * fatal-signal.m4 (gl_FATAL_SIGNAL): Require gt_TYPE_SIG_ATOMIC_T. + 2003-10-12 Paul Eggert <eggert@twinsun.com> * xalloc.m4 (gl_PREREQ_XMALLOC): Require AC_C_INLINE.
--- a/m4/fatal-signal.m4 +++ b/m4/fatal-signal.m4 @@ -1,4 +1,4 @@ -# fatal-signal.m4 serial 1 +# fatal-signal.m4 serial 2 dnl Copyright (C) 2003 Free Software Foundation, Inc. dnl This file is free software, distributed under the terms of the GNU dnl General Public License. As a special exception to the GNU General @@ -9,6 +9,7 @@ AC_DEFUN([gl_FATAL_SIGNAL], [ AC_REQUIRE([gt_SIGNALBLOCKING]) + AC_REQUIRE([gt_TYPE_SIG_ATOMIC_T]) AC_CHECK_HEADERS_ONCE(unistd.h) AC_CHECK_FUNCS(raise) ])