New lightweight Carp has a require. If Carp is used in a __DIE__ handler

this causes a POPSTACK panic. The problem seems to be that although
die_where() has unwound the tail of perl_vdie() top_env setjmp has been
set to resume execution there. Avoiding setting CATCH_SET(TRUE) in 
call_sv() avoids this. So invent a new G_NOCATCH flag to disable
messing with CATCH_SET() in call_sv, use it in perl_vdie().
Add test to op/eval.t which will fail (panic) if bug comes back.
>>> I AM NOT CONVINCED THIS IS CORRECT LONG TERM FIX <<<

p4raw-id: //depot/perl@3988

4 files changed, 20 insertions, 4 deletions

diff --git a/cop.h b/cop.h
index 84afd58967..f23251b543 100644
--- a/cop.h
+++ b/cop.h
@@ -297,6 +297,7 @@ struct context {
 #define G_NOARGS	8	/* Don't construct a @_ array. */
 #define G_KEEPERR      16	/* Append errors to $@, don't overwrite it */
 #define G_NODEBUG      32	/* Disable debugging at toplevel.  */
+#define G_NOCATCH      64       /* Don't do CATCH_SET() */
 
 /* flag bits for PL_in_eval */
 #define EVAL_NULL	0	/* not in an eval */
diff --git a/perl.c b/perl.c
index d81187989f..8c8b84c387 100644
--- a/perl.c
+++ b/perl.c
@@ -1225,10 +1225,16 @@ Perl_call_sv(pTHX_ SV *sv, I32 flags)
 	PL_op->op_private |= OPpENTERSUB_DB;
 
     if (!(flags & G_EVAL)) {
-	CATCH_SET(TRUE);
+        /* G_NOCATCH is a hack for perl_vdie using this path to call
+	   a __DIE__ handler */
+        if (!(flags & G_NOCATCH)) {
+	    CATCH_SET(TRUE);
+	}
 	call_xbody((OP*)&myop, FALSE);
 	retval = PL_stack_sp - (PL_stack_base + oldmark);
-	CATCH_SET(FALSE);
+        if (!(flags & G_NOCATCH)) {
+	    CATCH_SET(FALSE);
+	}
     }
     else {
 	cLOGOP->op_other = PL_op;
diff --git a/t/op/eval.t b/t/op/eval.t
index dc163e9e8f..abcb3794b7 100755
--- a/t/op/eval.t
+++ b/t/op/eval.t
@@ -1,6 +1,6 @@
 #!./perl
 
-print "1..36\n";
+print "1..37\n";
 
 eval 'print "ok 1\n";';
 
@@ -171,3 +171,8 @@ sub terminal { eval 'print $r' }
 }
 $x++;
 
+# Have we cured panic which occurred with require/eval in die handler ?
+$SIG{__DIE__} = sub { eval {1}; die shift }; 
+eval { die "ok ".$x++,"\n" }; 
+print $@;
+
diff --git a/util.c b/util.c
index 132ec5e127..715a5f1a15 100644
--- a/util.c
+++ b/util.c
@@ -1491,7 +1491,11 @@ Perl_vdie(pTHX_ const char* pat, va_list *args)
 	    PUSHMARK(SP);
 	    XPUSHs(msg);
 	    PUTBACK;
-	    call_sv((SV*)cv, G_DISCARD);
+	    /* HACK - REVISIT - avoid CATCH_SET(TRUE) in call_sv()
+	       or we come back here due to a JMPENV_JMP() and do 
+	       a POPSTACK - but die_where() will have already done 
+	       one as it unwound - NI-S 1999/08/14 */
+	    call_sv((SV*)cv, G_DISCARD|G_NOCATCH);
 	    POPSTACK;
 	    LEAVE;
 	}