From 789844e8d3708a63ffb4b2bc4d78bc780a4bb9d9 Mon Sep 17 00:00:00 2001
From: jjgarcia <jjgarcia>
Date: Thu, 11 Dec 2003 12:56:38 +0000
Subject: [PATCH] Use a lisp object to fill unbound slots rather than a null
 pointer which may end up causing SIGSEGV.

---
 src/c/instance.d     | 12 ++++++------
 src/c/symbols_list.h |  1 +
 src/cmp/sysfun.lsp   |  4 ++--
 src/h/object.h       |  1 +
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/c/instance.d b/src/c/instance.d
index 2c883e7d2..ad101f0e1 100644
--- a/src/c/instance.d
+++ b/src/c/instance.d
@@ -22,7 +22,7 @@ ecl_allocate_instance(cl_object clas, int size)
 	int i;
 	CLASS_OF(x) = clas;
 	for (i = 0;  i < size;  i++)
-		x->instance.slots[i] = OBJNULL;
+		x->instance.slots[i] = ECL_UNBOUND;
 	return(x);
 }
 
@@ -58,7 +58,7 @@ si_change_instance(cl_object x, cl_object clas, cl_object size, cl_object corr)
 	    corr = CDR(corr);
 	  }
 	  else
-	    x->instance.slots[i] = OBJNULL;
+	    x->instance.slots[i] = ECL_UNBOUND;
 	}
 	@(return) /* FIXME! Is this what we need? */
 }
@@ -116,7 +116,7 @@ si_instance_ref_safe(cl_object x, cl_object index)
 	    (i = fix(index)) < 0 || i >= x->instance.length)
 		FEerror("~S is an illegal slot index.", 1, index);
 	x = x->instance.slots[i];
-	if (x == OBJNULL)
+	if (x == ECL_UNBOUND)
 		FEerror("Slot index ~S unbound", 1, index);
 	@(return x)
 }
@@ -157,13 +157,13 @@ si_unbound()
 {
 	/* Returns an object that cannot be read or written and which
 	   is used to represent an unitialized slot */
-	@(return OBJNULL)
+	@(return ECL_UNBOUND)
 }
 
 cl_object
 si_sl_boundp(cl_object x)
 {
-	@(return ((x == OBJNULL) ? Cnil : Ct))
+	@(return ((x == ECL_UNBOUND) ? Cnil : Ct))
 }
 
 cl_object
@@ -176,7 +176,7 @@ si_sl_makunbound(cl_object x, cl_object index)
 	if (!FIXNUMP(index) ||
 	    (i = fix(index)) >= x->instance.length || i < 0)
 		FEerror("~S is an illegal slot index.", 1, index);
-	x->instance.slots[i] = OBJNULL;
+	x->instance.slots[i] = ECL_UNBOUND;
 	@(return x)
 }
 
diff --git a/src/c/symbols_list.h b/src/c/symbols_list.h
index 2d937f8b2..c15da66a6 100644
--- a/src/c/symbols_list.h
+++ b/src/c/symbols_list.h
@@ -18,6 +18,7 @@ cl_symbols[] = {
 
 {"NIL", CL_ORDINARY, NULL, -1},
 {"T", CL_ORDINARY, NULL, -1},
+{SYS_ "UNBOUND", SI_ORDINARY, NULL, -1, OBJNULL},
 
 /* LISP PACKAGE */
 {"&ALLOW-OTHER-KEYS", CL_ORDINARY, NULL, -1, OBJNULL},
diff --git a/src/cmp/sysfun.lsp b/src/cmp/sysfun.lsp
index 3440f6aa6..17dff379f 100644
--- a/src/cmp/sysfun.lsp
+++ b/src/cmp/sysfun.lsp
@@ -1049,9 +1049,9 @@ type_of(#0)==t_bitvector"))
 (si::INSTANCE-CLASS-SET (t t) T)
 (si::INSTANCEP (t) T nil t)
 (si::UNBOUND nil T nil t
-	:inline-always (nil T nil nil "OBJNULL"))
+	:inline-always (nil T nil nil "ECL_UNBOUND"))
 (si::SL-BOUNDP (t) T nil t
-	:inline-always ((t) :bool nil nil "(#0)!=OBJNULL"))
+	:inline-always ((t) :bool nil nil "(#0)!=ECL_UNBOUND"))
 (si::SL-MAKUNBOUND (t fixnum) T nil t)
 )) ; end of of #+clos
 
diff --git a/src/h/object.h b/src/h/object.h
index acb11424b..56887e38a 100644
--- a/src/h/object.h
+++ b/src/h/object.h
@@ -118,6 +118,7 @@ enum ecl_stype {		/*  symbol type  */
 
 #define	Cnil			((cl_object)cl_symbols)
 #define	Ct			((cl_object)(cl_symbols+1))
+#define ECL_UNBOUND		((cl_object)(cl_symbols+2))
 
 struct ecl_symbol {
 	HEADER4(stype, mflag, isform, dynamic);