decimal.diff

Index: bignum.c
===================================================================
--- bignum.c	(revision 23992)
+++ bignum.c	(working copy)
@@ -54,4 +54,10 @@ bigzero_p(VALUE x)
 
 int
+rb_bigzero_p(VALUE x)
+{
+    return BIGZEROP(x);
+}
+
+int
 rb_cmpint(VALUE val, VALUE a, VALUE b)
 {
Index: ext/decimal/decimal.c
===================================================================
--- ext/decimal/decimal.c	(revision 83)
+++ ext/decimal/decimal.c	(working copy)
@@ -427,18 +427,14 @@ dec_to_s(VALUE self)
     if (d == DEC_NINF) return rb_str_new2("-Infinity");
     if (d->inum == DEC_PZERO || d->inum == DEC_NZERO) {
-	const size_t HEAD_LEN = d->inum == DEC_PZERO ? 2U : 3U; /* "-0.".length */
-	long len = HEAD_LEN + d->scale;
-	char *buf;
-
 	/* FIXME: use "0eN" style when the scale is negative? */
 	if (d->scale <= 0) /* ignore the case of negative scale */
 	    return d->inum == DEC_PZERO ? rb_str_new2("0") : rb_str_new2("-0");
-	buf = xmalloc(len);
-	if (d->inum == DEC_PZERO)
-	    memcpy(buf, "0.", HEAD_LEN);
-	else
-	    memcpy(buf, "-0.", HEAD_LEN);
-	memset(buf + HEAD_LEN, '0', d->scale);
-	return rb_str_new(buf, len);
+#if SIZEOF_LONG > SIZEOF_INT
+	if (d->scale > INT_MAX) {
+	    rb_raise(rb_eArgError, "too big Decimal");
+	}
+#endif
+	return rb_sprintf("%s0.%0*d", (d->inum == DEC_PZERO ? "" : "-"),
+			  (int)d->scale, 0);
     }
     return finite_to_s(d);
@@ -827,4 +823,7 @@ do_round(Decimal *d, long scale, VALUE m
 	}
     }
+    else {
+	rb_bug("do_round(): invalid round mode");
+    }
   coda:
     if (negative) inum = INUM_UMINUS(inum);
Index: ext/decimal/inum19.h
===================================================================
--- ext/decimal/inum19.h	(revision 83)
+++ ext/decimal/inum19.h	(working copy)
@@ -15,18 +15,7 @@
 
 #define BDIGITS(x) (RBIGNUM_DIGITS(x))
-#define BIGZEROP(x) (RBIGNUM_LEN(x) == 0 || \
-		     (BDIGITS(x)[0] == 0 && \
-		      (RBIGNUM_LEN(x) == 1 || bigzero_p(x))))
-
-static int
-bigzero_p(VALUE x)
-{
-    long i;
-    for (i = RBIGNUM_LEN(x) - 1; 0 <= i; i--) {
-	if (BDIGITS(x)[i]) return 0;
-    }
-    return 1;
-}
+#define BIGZEROP(x) (rb_bigzero_p(x))
 
+int rb_bigzero_p(VALUE x);
 
 static VALUE