authorgravatar for git@vexu.euVeikka Tuominen <git@vexu.eu> 2021-06-11 19:17:01+03:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2021-06-11 10:31:08-07:00
loge3a74697f0317e1e6185262b477c0bfcad06d788
tree199edf57e8f0842414d9a6749fb2ff3ec890207b
parenta913311f3cf17c950facdf7aae16336fbdfbf8a9

Merge pull request #8330 from kivikakk/single-limb-bigint-overflow

bigint add failures with aliasing

2 files changed, 60 insertions(+), 7 deletions(-)

lib/std/math/big/int.zig+21-7
...@@ -316,7 +316,9 @@ pub const Mutable = struct {...@@ -316,7 +316,9 @@ pub const Mutable = struct {
316 }316 }
317317
318 if (a.limbs.len == 1 and b.limbs.len == 1 and a.positive == b.positive) {318 if (a.limbs.len == 1 and b.limbs.len == 1 and a.positive == b.positive) {
319 if (!@addWithOverflow(Limb, a.limbs[0], b.limbs[0], &r.limbs[0])) {319 var o: Limb = undefined;
320 if (!@addWithOverflow(Limb, a.limbs[0], b.limbs[0], &o)) {
321 r.limbs[0] = o;
320 r.len = 1;322 r.len = 1;
321 r.positive = a.positive;323 r.positive = a.positive;
322 return;324 return;
...@@ -333,10 +335,10 @@ pub const Mutable = struct {...@@ -333,10 +335,10 @@ pub const Mutable = struct {
333 }335 }
334 } else {336 } else {
335 if (a.limbs.len >= b.limbs.len) {337 if (a.limbs.len >= b.limbs.len) {
336 lladd(r.limbs[0..], a.limbs[0..a.limbs.len], b.limbs[0..b.limbs.len]);338 lladd(r.limbs[0..], a.limbs, b.limbs);
337 r.normalize(a.limbs.len + 1);339 r.normalize(a.limbs.len + 1);
338 } else {340 } else {
339 lladd(r.limbs[0..], b.limbs[0..b.limbs.len], a.limbs[0..a.limbs.len]);341 lladd(r.limbs[0..], b.limbs, a.limbs);
340 r.normalize(b.limbs.len + 1);342 r.normalize(b.limbs.len + 1);
341 }343 }
342344
...@@ -1683,12 +1685,14 @@ pub const Managed = struct {...@@ -1683,12 +1685,14 @@ pub const Managed = struct {
16831685
1684 /// r = a + scalar1686 /// r = a + scalar
1685 ///1687 ///
1686 /// r and a may be aliases.1688 /// r and a may be aliases. If r aliases a, then caller must call
1689 /// `r.ensureAddScalarCapacity` prior to calling `add`.
1687 /// scalar is a primitive integer type.1690 /// scalar is a primitive integer type.
1688 ///1691 ///
1689 /// Returns an error if memory could not be allocated.1692 /// Returns an error if memory could not be allocated.
1690 pub fn addScalar(r: *Managed, a: Const, scalar: anytype) Allocator.Error!void {1693 pub fn addScalar(r: *Managed, a: Const, scalar: anytype) Allocator.Error!void {
1691 try r.ensureCapacity(math.max(a.limbs.len, calcLimbLen(scalar)) + 1);1694 assert((r.limbs.ptr != a.limbs.ptr) or r.limbs.len >= math.max(a.limbs.len, calcLimbLen(scalar)) + 1);
1695 try r.ensureAddScalarCapacity(a, scalar);
1692 var m = r.toMutable();1696 var m = r.toMutable();
1693 m.addScalar(a, scalar);1697 m.addScalar(a, scalar);
1694 r.setMetadata(m.positive, m.len);1698 r.setMetadata(m.positive, m.len);
...@@ -1696,11 +1700,13 @@ pub const Managed = struct {...@@ -1696,11 +1700,13 @@ pub const Managed = struct {
16961700
1697 /// r = a + b1701 /// r = a + b
1698 ///1702 ///
1699 /// r, a and b may be aliases.1703 /// r, a and b may be aliases. If r aliases a or b, then caller must call
1704 /// `r.ensureAddCapacity` prior to calling `add`.
1700 ///1705 ///
1701 /// Returns an error if memory could not be allocated.1706 /// Returns an error if memory could not be allocated.
1702 pub fn add(r: *Managed, a: Const, b: Const) Allocator.Error!void {1707 pub fn add(r: *Managed, a: Const, b: Const) Allocator.Error!void {
1703 try r.ensureCapacity(math.max(a.limbs.len, b.limbs.len) + 1);1708 assert((r.limbs.ptr != a.limbs.ptr and r.limbs.ptr != b.limbs.ptr) or r.limbs.len >= math.max(a.limbs.len, b.limbs.len) + 1);
1709 try r.ensureAddCapacity(a, b);
1704 var m = r.toMutable();1710 var m = r.toMutable();
1705 m.add(a, b);1711 m.add(a, b);
1706 r.setMetadata(m.positive, m.len);1712 r.setMetadata(m.positive, m.len);
...@@ -1746,6 +1752,14 @@ pub const Managed = struct {...@@ -1746,6 +1752,14 @@ pub const Managed = struct {
1746 rma.setMetadata(m.positive, m.len);1752 rma.setMetadata(m.positive, m.len);
1747 }1753 }
17481754
1755 pub fn ensureAddScalarCapacity(r: *Managed, a: Const, scalar: anytype) !void {
1756 try r.ensureCapacity(math.max(a.limbs.len, calcLimbLen(scalar)) + 1);
1757 }
1758
1759 pub fn ensureAddCapacity(r: *Managed, a: Const, b: Const) !void {
1760 try r.ensureCapacity(math.max(a.limbs.len, b.limbs.len) + 1);
1761 }
1762
1749 pub fn ensureMulCapacity(rma: *Managed, a: Const, b: Const) !void {1763 pub fn ensureMulCapacity(rma: *Managed, a: Const, b: Const) !void {
1750 try rma.ensureCapacity(a.limbs.len + b.limbs.len + 1);1764 try rma.ensureCapacity(a.limbs.len + b.limbs.len + 1);
1751 }1765 }
lib/std/math/big/int_test.zig+39
...@@ -538,6 +538,17 @@ test "big.int add sign" {...@@ -538,6 +538,17 @@ test "big.int add sign" {
538 try testing.expect((try a.to(i32)) == -3);538 try testing.expect((try a.to(i32)) == -3);
539}539}
540540
541test "big.int add scalar" {
542 var a = try Managed.initSet(testing.allocator, 50);
543 defer a.deinit();
544
545 var b = try Managed.init(testing.allocator);
546 defer b.deinit();
547 try b.addScalar(a.toConst(), 5);
548
549 try testing.expect((try b.to(u32)) == 55);
550}
551
541test "big.int sub single-single" {552test "big.int sub single-single" {
542 var a = try Managed.initSet(testing.allocator, 50);553 var a = try Managed.initSet(testing.allocator, 50);
543 defer a.deinit();554 defer a.deinit();
...@@ -1562,3 +1573,31 @@ test "big.int pow" {...@@ -1562,3 +1573,31 @@ test "big.int pow" {
1562 try testing.expectEqual(@as(i32, 1), try a.to(i32));1573 try testing.expectEqual(@as(i32, 1), try a.to(i32));
1563 }1574 }
1564}1575}
1576
1577test "big.int regression test for 1 limb overflow with alias" {
1578 // Note these happen to be two consecutive Fibonacci sequence numbers, the
1579 // first two whose sum exceeds 2**64.
1580 var a = try Managed.initSet(testing.allocator, 7540113804746346429);
1581 defer a.deinit();
1582 var b = try Managed.initSet(testing.allocator, 12200160415121876738);
1583 defer b.deinit();
1584
1585 try a.ensureAddCapacity(a.toConst(), b.toConst());
1586 try a.add(a.toConst(), b.toConst());
1587
1588 try testing.expect(a.toConst().orderAgainstScalar(19740274219868223167) == .eq);
1589}
1590
1591test "big.int regression test for realloc with alias" {
1592 // Note these happen to be two consecutive Fibonacci sequence numbers, the
1593 // second of which is the first such number to exceed 2**192.
1594 var a = try Managed.initSet(testing.allocator, 5611500259351924431073312796924978741056961814867751431689);
1595 defer a.deinit();
1596 var b = try Managed.initSet(testing.allocator, 9079598147510263717870894449029933369491131786514446266146);
1597 defer b.deinit();
1598
1599 try a.ensureAddCapacity(a.toConst(), b.toConst());
1600 try a.add(a.toConst(), b.toConst());
1601
1602 try testing.expect(a.toConst().orderAgainstScalar(14691098406862188148944207245954912110548093601382197697835) == .eq);
1603}