Also trap SIGILL, SIGFPE, SIGBUS.

* m4/gnulib-cache.m4: Import strsignal module.
* src/m4.c (main): Register more handlers, and prefer sigaction
when available.
(SIGBUS, NSIG): Provide fallback when lacking.
(signal_message): New variable, to keep async-safety.
(fault_handler): Display faulting signal description.
* configure.ac (gl_DISABLE_THREADS): Request gnulib modules to
optimize for single-threaded operation.

Signed-off-by: Eric Blake <ebb9@byu.net>

4 files changed, 71 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 6dc4932d..9913112a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2008-06-18  Eric Blake  <ebb9@byu.net>
+
+	Also trap SIGILL, SIGFPE, SIGBUS.
+	* m4/gnulib-cache.m4: Import strsignal module.
+	* src/m4.c (main): Register more handlers, and prefer sigaction
+	when available.
+	(SIGBUS, NSIG): Provide fallback when lacking.
+	(signal_message): New variable, to keep async-safety.
+	(fault_handler): Display faulting signal description.
+	* configure.ac (gl_DISABLE_THREADS): Request gnulib modules to
+	optimize for single-threaded operation.
+
 2008-06-06  Eric Blake  <ebb9@byu.net>
 
 	Inform users what to do in case of programmer error.
diff --git a/configure.ac b/configure.ac
index 3456d8fe..f23cc422 100644
--- a/configure.ac
+++ b/configure.ac
@@ -32,6 +32,9 @@ AC_CONFIG_HEADERS([lib/config.h:lib/config.hin])
 AC_PROG_CC
 M4_EARLY
 
+# M4 is single-threaded; so we can optimize gnulib code by using this:
+gl_DISABLE_THREADS
+
 # Tandem/NSK is broken - it has 'long long int' but not
 # 'unsigned long long int', which confuses assumptions made by gnulib.
 # Simply pretend that neither type exists if both do not work.
diff --git a/m4/gnulib-cache.m4 b/m4/gnulib-cache.m4
index 7c1fb0d6..7f8d10be 100644
--- a/m4/gnulib-cache.m4
+++ b/m4/gnulib-cache.m4
@@ -15,11 +15,11 @@
 
 
 # Specification in the form of a command-line invocation:
-#   gnulib-tool --import --dir=. --local-dir=local --lib=libm4 --source-base=lib --m4-base=m4 --doc-base=doc --aux-dir=build-aux --with-tests --no-libtool --macro-prefix=M4 announce-gen assert autobuild avltree-oset binary-io c-stack clean-temp cloexec close-stream closein config-h error fdl fflush flexmember fopen-safer fseeko gendocs getopt git-version-gen gnumakefile gnupload gpl-3.0 intprops memchr2 memmem mkstemp obstack progname quote regex stdbool stdint stdlib-safer strtod strtol unlocked-io vasnprintf-posix verror version-etc version-etc-fsf xalloc xmemdup0 xprintf xvasprintf-posix
+#   gnulib-tool --import --dir=. --local-dir=local --lib=libm4 --source-base=lib --m4-base=m4 --doc-base=doc --aux-dir=build-aux --with-tests --no-libtool --macro-prefix=M4 announce-gen assert autobuild avltree-oset binary-io c-stack clean-temp cloexec close-stream closein config-h error fdl fflush flexmember fopen-safer fseeko gendocs getopt git-version-gen gnumakefile gnupload gpl-3.0 intprops memchr2 memmem mkstemp obstack progname quote regex stdbool stdint stdlib-safer strsignal strtod strtol unlocked-io vasnprintf-posix verror version-etc version-etc-fsf xalloc xmemdup0 xprintf xvasprintf-posix
 
 # Specification in the form of a few gnulib-tool.m4 macro invocations:
 gl_LOCAL_DIR([local])
-gl_MODULES([announce-gen assert autobuild avltree-oset binary-io c-stack clean-temp cloexec close-stream closein config-h error fdl fflush flexmember fopen-safer fseeko gendocs getopt git-version-gen gnumakefile gnupload gpl-3.0 intprops memchr2 memmem mkstemp obstack progname quote regex stdbool stdint stdlib-safer strtod strtol unlocked-io vasnprintf-posix verror version-etc version-etc-fsf xalloc xmemdup0 xprintf xvasprintf-posix])
+gl_MODULES([announce-gen assert autobuild avltree-oset binary-io c-stack clean-temp cloexec close-stream closein config-h error fdl fflush flexmember fopen-safer fseeko gendocs getopt git-version-gen gnumakefile gnupload gpl-3.0 intprops memchr2 memmem mkstemp obstack progname quote regex stdbool stdint stdlib-safer strsignal strtod strtol unlocked-io vasnprintf-posix verror version-etc version-etc-fsf xalloc xmemdup0 xprintf xvasprintf-posix])
 gl_AVOID([])
 gl_SOURCE_BASE([lib])
 gl_M4_BASE([m4])
diff --git a/src/m4.c b/src/m4.c
index f2c7c61a..a6665ff8 100644
--- a/src/m4.c
+++ b/src/m4.c
@@ -178,9 +178,23 @@ m4_warn (int errnum, const call_info *caller, const char *format, ...)
     }
 }
 
-/* Translated message for program errors.  Do not translate it in the
-   signal handler, since gettext is not async-signal-safe.  */
+#ifndef SIGBUS
+# define SIGBUS SIGILL
+#endif
+
+#ifndef NSIG
+# ifndef MAX
+#  define MAX(a,b) ((a) < (b) ? (b) : (a))
+# endif
+# define NSIG (MAX (SIGABRT, MAX (SIGILL, MAX (SIGFPE,  \
+                                               MAX (SIGSEGV, SIGBUS)))) + 1)
+#endif
+
+/* Pre-translated messages for program errors.  Do not translate in
+   the signal handler, since gettext and strsignal are not
+   async-signal-safe.  */
 static const char * volatile program_error_message;
+static const char * volatile signal_message[NSIG];
 
 /* Print a nicer message about any programmer errors, then exit.  This
    must be aysnc-signal safe, since it is executed as a signal
@@ -191,10 +205,21 @@ fault_handler (int signo)
 {
   if (signo)
     {
+      /* POSIX states that reading static memory is, in general, not
+         async-safe.  However, the static variables that we read are
+         never modified once this handler is installed, so this
+         particular usage is safe.  And it seems an oversight that
+         POSIX claims strlen is not async-safe.  */
       write (STDERR_FILENO, program_name, strlen (program_name));
       write (STDERR_FILENO, ": ", 2);
       write (STDERR_FILENO, program_error_message,
              strlen (program_error_message));
+      if (signal_message[signo])
+        {
+          write (STDERR_FILENO, ": ", 2);
+          write (STDERR_FILENO, signal_message[signo],
+                 strlen (signal_message[signo]));
+        }
       write (STDERR_FILENO, "\n", 1);
       _exit (EXIT_INTERNAL_ERROR);
     }
@@ -438,14 +463,39 @@ main (int argc, char *const *argv, char *const *envp)
   set_quoting_style (NULL, escape_quoting_style);
   set_char_quoting (NULL, ':', 1);
 
-  /* Stack overflow and program error handling.  */
+  /* Stack overflow and program error handling.  Ignore failure to
+     install a handler, since this is merely for improved output on
+     crash, and we should never crash ;).  */
   if (c_stack_action (fault_handler) == 0)
     nesting_limit = 0;
   program_error_message
     = xasprintf (_("internal error detected; please report this bug to <%s>"),
                  PACKAGE_BUGREPORT);
-  /* FIXME - use sigaction.  */
+  signal_message[SIGSEGV] = xstrdup (strsignal (SIGSEGV));
+  signal_message[SIGABRT] = xstrdup (strsignal (SIGABRT));
+  signal_message[SIGILL] = xstrdup (strsignal (SIGILL));
+  signal_message[SIGFPE] = xstrdup (strsignal (SIGFPE));
+  if (SIGBUS != SIGILL)
+    signal_message[SIGBUS] = xstrdup (strsignal (SIGBUS));
+#ifdef HAVE_SIGACTION
+  {
+    struct sigaction act;
+    sigemptyset (&act.sa_mask);
+    /* One-shot - if we fault while handling a fault, we want to
+       revert to default signal behavior.  */
+    act.sa_flags = SA_NODEFER | SA_RESETHAND;
+    act.sa_handler = fault_handler;
+    sigaction (SIGABRT, &act, NULL);
+    sigaction (SIGILL, &act, NULL);
+    sigaction (SIGFPE, &act, NULL);
+    sigaction (SIGBUS, &act, NULL);
+  }
+#else /* !HAVE_SIGACTION */
   signal (SIGABRT, fault_handler);
+  signal (SIGILL, fault_handler);
+  signal (SIGFPE, fault_handler);
+  signal (SIGBUS, fault_handler);
+#endif /* !HAVE_SIGACTION */
 
   /* First, we decode the arguments, to size up tables and stuff.  */