erts: Fix bug in bxor of a big negative number

Wrong result for

(X bsl WS) bxor Y.

where
X is any negative integer
Y is any integer that does not require more words than X
WS is erlang:system_info(wordsize) or larger


Fix: The subtraction of 1 (for 2-complement conversion)
must be carried along all the way to the last words.

1 files changed, 8 insertions, 3 deletions

diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c
index d1e46e3063..323cd6c518 100644
--- a/erts/emulator/beam/big.c
+++ b/erts/emulator/beam/big.c
@@ -1273,8 +1273,11 @@ static dsize_t I_bxor(ErtsDigit* x, dsize_t xl, short xsgn,
 		*r++ = ~c ^ *y++;
 		x++;
 	    }
-	    while(xl--)
-		*r++ = ~*x++;
+	    while(xl--) {
+		DSUBb(*x,0,b,c);
+		*r++ = ~c;
+		x++;
+	    }
 	}
 	else {
 	    ErtsDigit b1, b2;
@@ -1292,7 +1295,9 @@ static dsize_t I_bxor(ErtsDigit* x, dsize_t xl, short xsgn,
 		x++; y++;
 	    }
 	    while(xl--) {
-		*r++ = *x++;
+                DSUBb(*x,0,b1,c1);
+		*r++ = c1;
+                x++;
 	    }
 	}
     }