Integrate perlio:

[  8408]
Remove variables that were used in experiments.

[  8407]
Catch die in %SIG handler and unblock the signal before re-dying.
This make Linux work _without_ sigsetjmp().
Turn off sigsetjmp() to see what else it does.
May need Configure probe for sigprocmask() if anything has sigaction()
but not sigprocmask().

p4raw-link: @8408 on //depot/perlio: e86d18f
p4raw-link: @8407 on //depot/perlio: 1b26641

p4raw-id: //depot/perl@8409

mg.c

@@ -2223,9 +2223,26 @@ Perl_sighandler(int sig)
     PUSHs(sv);
     PUTBACK;
 
-    call_sv((SV*)cv, G_DISCARD);
+    call_sv((SV*)cv, G_DISCARD|G_EVAL);
 
     POPSTACK;
+    if (SvTRUE(ERRSV)) {
+#ifdef HAS_SIGACTION
+	/* Handler "died", for example to get out of a restart-able read().
+	 * Before we re-do that on its behalf re-enable the signal which was
+	 * blocked by the system when we entered.
+	 */
+	sigset_t set;
+	sigemptyset(&set);
+	sigaddset(&set,sig);
+	sigprocmask(SIG_UNBLOCK, &set, NULL);
+#else
+	/* Not clear if this will work */
+	(void)rsignal(sig, SIG_IGN);
+	(void)rsignal(sig, PL_sighandlerp);
+#endif
+	Perl_die(aTHX_ Nullch);
+    }
 cleanup:
     if (flags & 1)
 	PL_savestack_ix -= 8; /* Unprotect save in progress. */

scope.h

@@ -36,7 +36,7 @@
 #define SAVEt_PADSV		35
 
 #ifndef SCOPE_SAVES_SIGNAL_MASK
-#define SCOPE_SAVES_SIGNAL_MASK 1
+#define SCOPE_SAVES_SIGNAL_MASK 0
 #endif
 
 #define SSCHECK(need) if (PL_savestack_ix + need > PL_savestack_max) savestack_grow()