From cb7eaa7fe6e5172578bd5e57bd527672c3ac2bf0 Mon Sep 17 00:00:00 2001
From: Alex Shinn <alexshinn@gmail.com>
Date: Sun, 7 May 2017 16:36:12 +0900
Subject: [PATCH] fixing bitwise-xor for negative bignum cases

---
 lib/srfi/142/bit.c    | 8 ++++++--
 lib/srfi/142/test.sld | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/srfi/142/bit.c b/lib/srfi/142/bit.c
index e80e17bd..3dae9eab 100644
--- a/lib/srfi/142/bit.c
+++ b/lib/srfi/142/bit.c
@@ -131,9 +131,9 @@ sexp sexp_bit_ior (sexp ctx, sexp self, sexp_sint_t n, sexp x, sexp y) {
         sexp_set_twos_complement(res);
       for (i=0; i<len; i++)
         sexp_bignum_data(res)[i] |= sexp_bignum_data(tmp)[i];
-      if ((sexp_bignum_sign(res) < 0) ^ sexp_fixnump(y))
+      if ((sexp_bignum_sign(x) < 0) ^ (sexp_fixnump(y) || sexp_bignum_sign(y) < 0))
         sexp_set_twos_complement(res);
-      if (sexp_fixnump(y)) {
+      if (sexp_fixnump(y) || sexp_bignum_sign(y) < 0) {
         sexp_negate_exact(res);
       }
     } else {
@@ -188,6 +188,10 @@ sexp sexp_bit_xor (sexp ctx, sexp self, sexp_sint_t n, sexp x, sexp y) {
           = sexp_bignum_data(res)[i] ^ sexp_bignum_data(tmp)[i];
       if (sexp_bignum_sign(res) < 0)
         sexp_set_twos_complement(res);
+      if  (!((sexp_bignum_sign(x) < 0) ^ (sexp_bignum_sign(y) < 0))) {
+        sexp_set_twos_complement(res);
+        sexp_negate_exact(res);
+      }
     } else {
       res = sexp_type_exception(ctx, self, SEXP_FIXNUM, y);
     }
diff --git a/lib/srfi/142/test.sld b/lib/srfi/142/test.sld
index 0d4cef77..55db18b3 100644
--- a/lib/srfi/142/test.sld
+++ b/lib/srfi/142/test.sld
@@ -35,6 +35,9 @@
       (test -461856550205267621490541042387407516495872
           (bitwise-xor -1930735170000000000001689392892000000000000
                        1689392892000000000000193073517000000000000))
+      (test 461856550205267621490541042387407516495872
+          (bitwise-xor -1930735170000000000001689392892000000000000
+                       -1689392892000000000000193073517000000000000))
       (test 3769478 (bitwise-and 1694076839 -4290775858))
       (test 1680869008 (bitwise-and -193073517 1689392892))