diff --git a/ChangeLog b/ChangeLog
index 298e4b94b5..cd13554066 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -8,9 +8,9 @@ Wed Apr  9 14:05:00 2003  Nobuyoshi Nakada  <nobu.nokada@softhome.net>
 	* marshal.c (w_object): preserve extended module on struct.
 	  (ruby-bugs-ja:PR#422)
 
-Tue Apr  8 17:13:53 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
+Wed Apr  9 03:43:14 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
-	* random.c (rb_f_rand): normalize bignum argument.
+	* bignum.c (BIGZEROP): macro to determine if x is a bignum zero.
 
 Tue Apr  8 11:49:31 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
diff --git a/bignum.c b/bignum.c
index 577f072ee3..0ae88ab713 100644
--- a/bignum.c
+++ b/bignum.c
@@ -33,6 +33,8 @@ VALUE rb_cBignum;
 #define BIGLO(x) ((BDIGIT)((x) & (BIGRAD-1)))
 #define BDIGMAX ((BDIGIT)-1)
 
+#define BIGZEROP(x) (RBIGNUM(x)->len == 0 || (RBIGNUM(x)->len == 1 && BDIGITS(x)[0] == 0))
+
 static VALUE
 bignew_1(klass, len, sign)
     VALUE klass;
@@ -612,7 +614,7 @@ rb_big2str(x, base)
 	return rb_fix2str(x, base);
     }
     i = RBIGNUM(x)->len;
-    if (i == 0 || (i == 1 && BDIGITS(x)[0] == 0)) {
+    if (BIGZEROP(x)) {
 	return rb_str_new2("0");
     }
     if (base == 10) {
@@ -1123,8 +1125,8 @@ bigdivrem(x, y, divp, modp)
     BDIGIT_DBL_SIGNED num;
     BDIGIT dd, q;
 
+    if (BIGZEROP(y)) rb_num_zerodiv();
     yds = BDIGITS(y);
-    if (ny == 0 && yds[0] == 0) rb_num_zerodiv();
     if (nx < ny || (nx == ny && BDIGITS(x)[nx - 1] < BDIGITS(y)[ny - 1])) {
 	if (divp) *divp = rb_int2big(0);
 	if (modp) *modp = x;
@@ -1248,8 +1250,7 @@ bigdivmod(x, y, divp, modp)
     VALUE mod;
 
     bigdivrem(x, y, divp, &mod);
-    if (RBIGNUM(x)->sign != RBIGNUM(y)->sign &&
-	!(RBIGNUM(mod)->len == 1 && BDIGITS(mod)[0] == 0)) {
+    if (RBIGNUM(x)->sign != RBIGNUM(y)->sign && !BIGZEROP(x)) {
 	if (divp) *divp = bigadd(*divp, rb_int2big(1), 0);
 	if (modp) *modp = bigadd(mod, y, 1);
     }
@@ -1728,8 +1729,8 @@ rb_big_rand(max, rand_buf)
 {
     VALUE v;
     long len = RBIGNUM(max)->len;
-    
-    if (len == 0 && BDIGITS(max)[0] == 0) {
+
+    if (BIGZEROP(max)) {
 	return rb_float_new(rand_buf[0]);
     }
     v = bignew(len,1);
diff --git a/eval.c b/eval.c
index 5ffcdb04c8..c2fdd158dd 100644
--- a/eval.c
+++ b/eval.c
@@ -5083,7 +5083,7 @@ backtrace(lev)
 {
     struct FRAME *frame = ruby_frame;
     char buf[BUFSIZ];
-    VALUE ary;
+    volatile VALUE ary;
     NODE *n;
 
     ary = rb_ary_new();
diff --git a/gc.c b/gc.c
index 6c8e9f650e..57e1ebac8f 100644
--- a/gc.c
+++ b/gc.c
@@ -381,9 +381,11 @@ static unsigned int STACK_LEVEL_MAX = 655300;
                                            : STACK_END - rb_gc_stack_start)
 #endif
 
+#define GC_WARTER_MARK 512
+
 #define CHECK_STACK(ret) do {\
     SET_STACK_END;\
-    (ret) = (STACK_LENGTH > STACK_LEVEL_MAX);\
+    (ret) = (STACK_LENGTH > STACK_LEVEL_MAX + GC_WARTER_MARK);\
 } while (0)
 
 int
@@ -460,25 +462,6 @@ sweep_source_filename(key, value)
     }
 }
 
-static void
-gc_mark_all()
-{
-    RVALUE *p, *pend;
-    int i;
-
-    init_mark_stack();
-    for (i = 0; i < heaps_used; i++) {
-	p = heaps[i]; pend = p + heaps_limits[i];
-	while (p < pend) {
-	    if ((p->as.basic.flags & FL_MARK) &&
-		(p->as.basic.flags != FL_MARK)) {
-		rb_gc_mark((VALUE)p);
-	    }
-	    p++;
-	}
-    }
-}
-
 static void
 gc_mark_rest()
 {
@@ -491,10 +474,32 @@ gc_mark_rest()
     init_mark_stack();
     while(p != tmp_arry){
 	p--;
+	FL_UNSET(*p, FL_MARK);
 	rb_gc_mark(*p);
     }
 }
 
+static void
+gc_mark_all()
+{
+    RVALUE *p, *pend;
+    int i;
+
+    gc_mark_rest();
+    init_mark_stack();
+    for (i = 0; i < heaps_used; i++) {
+	p = heaps[i]; pend = p + heaps_limits[i];
+	while (p < pend) {
+	    if ((p->as.basic.flags & FL_MARK) &&
+		(p->as.basic.flags != FL_MARK)) {
+		FL_UNSET(p, FL_MARK);
+		rb_gc_mark((VALUE)p);
+	    }
+	    p++;
+	}
+    }
+}
+
 static inline int
 is_pointer_to_heap(ptr)
     void *ptr;
@@ -597,6 +602,11 @@ rb_gc_mark(ptr)
 
     CHECK_STACK(ret);
     if (ret) {
+	obj = RANY(ptr);
+	if (rb_special_const_p(ptr)) return; /* special const not marked */
+	if (obj->as.basic.flags == 0) return;       /* free cell */
+	if (obj->as.basic.flags & FL_MARK) return;  /* already marked */ 
+	obj->as.basic.flags |= FL_MARK;
 	if (!mark_stack_overflow) {
 	    if (mark_stack_ptr - mark_stack < MARK_STACK_MAX) {
 		*mark_stack_ptr = ptr;
diff --git a/random.c b/random.c
index b04bcddb8f..86c8198d41 100644
--- a/random.c
+++ b/random.c
@@ -215,11 +215,6 @@ rb_f_rand(argc, argv, obj)
 	vmax = rb_dbl2big(RFLOAT(vmax)->value);
 	/* fall through */
       case T_BIGNUM:
-	vmax = rb_big_norm(vmax);
-	if (FIXNUM_P(vmax)) {
-	    max = FIX2INT(vmax);
-	    break;
-	}
       bignum:
         {
 	    long len = RBIGNUM(vmax)->len;