pitrou commented on a change in pull request #9395:
URL: https://github.com/apache/arrow/pull/9395#discussion_r571938500
##########
File path: cpp/src/arrow/tensor.cc
##########
@@ -127,14 +162,31 @@ Status CheckTensorStridesValidity(const
std::shared_ptr<Buffer>& data,
return Status::OK();
}
- std::vector<int64_t> last_index(shape);
- const int64_t n = static_cast<int64_t>(shape.size());
- for (int64_t i = 0; i < n; ++i) {
- --last_index[i];
+ // Check the largest offset can be computed without overflow
+ const size_t ndim = shape.size();
+ int64_t largest_offset = 0;
+ for (size_t i = 0; i < ndim; ++i) {
+ if (shape[i] == 0) continue;
+
+ int64_t dim_offset;
+ if (!internal::MultiplyWithOverflow(shape[i] - 1, strides[i],
&dim_offset)) {
+ if (dim_offset <= 0) {
+ // Ignore the negative dim_offset here because we are interested in
only the
+ // largest offset
Review comment:
That doesn't seem right. What if all strides are negative?
It seems you must maintain two separate offsets: a largest positive one, and
a largest negative one.
##########
File path: cpp/src/arrow/tensor_test.cc
##########
@@ -152,6 +243,22 @@ TEST(TestTensor, MakeFailureCases) {
// negative items in shape
ASSERT_RAISES(Invalid, Tensor::Make(float64(), data, {-3, 6}));
+ // overflow in stride computation
+ constexpr uint64_t total_length =
+ 1 + static_cast<uint64_t>(std::numeric_limits<int64_t>::max());
+ EXPECT_RAISES_WITH_MESSAGE_THAT(
+ Invalid,
+ testing::HasSubstr(
+ "Row-major strides computed from shape would not fit in 64-bit
integer"),
+ Tensor::Make(float64(), data, {2, 2, static_cast<int64_t>(total_length /
4)}));
+
+ // overflow by negative multiplication in strides validity check
+ EXPECT_RAISES_WITH_MESSAGE_THAT(
+ Invalid, testing::HasSubstr("would not fit in 64-bit integer"),
+ Tensor::Make(
+ float64(), data, {0, 4, 0},
+ {sizeof(double), -static_cast<int64_t>(total_length / 2),
sizeof(double)}));
Review comment:
What if, for example, `shape = {3, total_length / 3}` and `strides =
{-total_length / 3, -1}`?
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