Buffer serialization does not match deserialization

[abadams]

We're currently getting failures for correctness_image_io, but only when the serialization round trip testing is enabled. I think it's likely that serializing buffers is wonky, but I don't know why this would have only just broken now. The serialization code is:

   for (int i = 0; i < buffer.dimensions(); ++i) {
        int32_t min = buffer.dim(i).min();
        int32_t extent = buffer.dim(i).extent();
        int32_t stride = buffer.dim(i).stride();
        buffer_dimensions_serialized.push_back(Serialize::CreateBufferDimension(builder, min, extent, stride));
    }
    auto copy = buffer.copy();  // compact in memory
    std::vector<uint8_t> data;
    data.resize(copy.size_in_bytes());
    memcpy(data.data(), copy.data(), copy.size_in_bytes());

and the deserialization code is:

   for (int i = 0; i < dimensions; ++i) {
        const auto *dim = buffer->dims()->Get(i);
        halide_dimension_t hl_dim, dense_dim;
        hl_dim.min = dim->min();
        hl_dim.extent = dim->extent();
        hl_dim.stride = dim->stride();
        hl_buffer_dimensions.push_back(hl_dim);
        dense_dim.min = hl_dim.min;
        dense_dim.extent = hl_dim.extent;
        if (i == 0) {
            dense_dim.stride = hl_dim.stride;
            stride = hl_dim.stride * hl_dim.extent;
        } else {
            dense_dim.stride = stride;
            stride *= hl_dim.extent;
        }
        dense_buffer_dimensions.push_back(dense_dim);
    }
    // To handle cropped buffer, we create a dense buffer and serialize into it,
    // then create a (potential sparse) buffer with orignal dimension infos and copy from the dense buffer
    auto fake_dense_buffer = Buffer<>(type, nullptr, dimensions, dense_buffer_dimensions.data(), name + "_dense_fake");
    auto dense_buffer = Buffer<>::make_with_shape_of(fake_dense_buffer, nullptr, nullptr, name + "_dense_tmp");
    memcpy(dense_buffer.data(), buffer->data()->data(), buffer->data()->size());
    auto fake_buffer = Buffer<>(type, nullptr, dimensions, hl_buffer_dimensions.data(), name + "_fake");
    auto hl_buffer = Buffer<>::make_with_shape_of(fake_buffer, nullptr, nullptr, name);
    hl_buffer.copy_from(dense_buffer);

The deserialization code appears to assume that the strides are in increasing order, which buffer.copy() does not guarantee (it preserves dimension ordering). I will attempt to fix.

[abadams]

Red herring, the problem was actually due to a clang tidy false positive in #8509