From: Nobuyoshi Nakada <nobu@...>
Date: 2007-07-23T03:14:55+09:00
Subject: [ruby-dev:31273] Re: (1 << 0x40000000)[0x40000000]

なかだです。

At Mon, 23 Jul 2007 00:35:30 +0900,
Tanaka Akira wrote in [ruby-dev:31271]:
> 次のように、(1 << 0x40000000)[0x40000000] が 0 になります。
(以下略)


Index: trunk/bignum.c
===================================================================
--- trunk/bignum.c	(revision 12828)
+++ trunk/bignum.c	(working copy)
@@ -2062,27 +2062,37 @@ rb_big_aref(VALUE x, VALUE y)
 {
     BDIGIT *xds;
-    int shift;
-    long s1, s2;
+    BDIGIT_DBL num;
+    VALUE shift;
+    long i, s1, s2;
 
     if (TYPE(y) == T_BIGNUM) {
-	if (!RBIGNUM(y)->sign || RBIGNUM(x)->sign)
+	if (!RBIGNUM(y)->sign)
 	    return INT2FIX(0);
-	return INT2FIX(1);
+	if (RBIGNUM(bigtrunc(y))->len > SIZEOF_VALUE/SIZEOF_BDIGITS) {
+	  out_of_range:
+	    return RBIGNUM(x)->sign ? INT2FIX(0) : INT2FIX(1);
+	}
+	shift = big2ulong(y, "long", Qfalse);
+    }
+    else {
+	i = NUM2LONG(y);
+	if (i < 0) return INT2FIX(0);
+	shift = (VALUE)i;
     }
-    shift = NUM2INT(y);
-    if (shift < 0) return INT2FIX(0);
     s1 = shift/BITSPERDIG;
     s2 = shift%BITSPERDIG;
 
+    if (s1 >= RBIGNUM(x)->len) goto out_of_range;
     if (!RBIGNUM(x)->sign) {
-	if (s1 >= RBIGNUM(x)->len) return INT2FIX(1);
-	x = rb_big_clone(x);
-	get2comp(x);
+	xds = BDIGITS(x);
+	i = 0; num = 1;
+	while (num += ~xds[i], ++i <= s1) {
+	    num = BIGDN(num);
+	}
     }
     else {
-	if (s1 >= RBIGNUM(x)->len) return INT2FIX(0);
+	num = BDIGITS(x)[s1];
     }
-    xds = BDIGITS(x);
-    if (xds[s1] & (1<<s2))
+    if (num & ((BDIGIT_DBL)1<<s2))
 	return INT2FIX(1);
     return INT2FIX(0);
Index: stable/bignum.c
===================================================================
--- stable/bignum.c	(revision 12828)
+++ stable/bignum.c	(working copy)
@@ -2152,27 +2152,37 @@ rb_big_aref(x, y)
 {
     BDIGIT *xds;
-    int shift;
-    long s1, s2;
+    BDIGIT_DBL num;
+    unsigned long shift;
+    long i, s1, s2;
 
     if (TYPE(y) == T_BIGNUM) {
-	if (!RBIGNUM(y)->sign || RBIGNUM(x)->sign)
+	if (!RBIGNUM(y)->sign)
 	    return INT2FIX(0);
-	return INT2FIX(1);
+	if (RBIGNUM(bigtrunc(y))->len > SIZEOF_LONG/SIZEOF_BDIGITS) {
+	  out_of_range:
+	    return RBIGNUM(x)->sign ? INT2FIX(0) : INT2FIX(1);
+	}
+	shift = big2ulong(y, "long", Qfalse);
+    }
+    else {
+	i = NUM2LONG(y);
+	if (i < 0) return INT2FIX(0);
+	shift = (VALUE)i;
     }
-    shift = NUM2INT(y);
-    if (shift < 0) return INT2FIX(0);
     s1 = shift/BITSPERDIG;
     s2 = shift%BITSPERDIG;
 
+    if (s1 >= RBIGNUM(x)->len) goto out_of_range;
     if (!RBIGNUM(x)->sign) {
-	if (s1 >= RBIGNUM(x)->len) return INT2FIX(1);
-	x = rb_big_clone(x);
-	get2comp(x);
+	xds = BDIGITS(x);
+	i = 0; num = 1;
+	while (num += ~xds[i], ++i <= s1) {
+	    num = BIGDN(num);
+	}
     }
     else {
-	if (s1 >= RBIGNUM(x)->len) return INT2FIX(0);
+	num = BDIGITS(x)[s1];
     }
-    xds = BDIGITS(x);
-    if (xds[s1] & (1<<s2))
+    if (num & ((BDIGIT_DBL)1<<s2))
 	return INT2FIX(1);
     return INT2FIX(0);


-- 
--- 僕の前にBugはない。
--- 僕の後ろにBugはできる。
    中田 伸悦