Add a memory safety test (#129)

* initial commit of memory safety test

* Clean up, document test

* Tweak documentation

---------

Co-authored-by: Rahul <[email protected]>

crates/openvino/tests/memory-safety.rs

@@ -0,0 +1,36 @@
+//! This test originates from some strange segfaults that we observed while using the OpenVINO C
+//! library. Because OpenVINO is taking a pointer to a tensor when constructing a model, we want to
+//! be sure that we do the right thing on this side of the FFI boundary.
+
+mod fixtures;
+
+use fixtures::mobilenet::Fixture;
+use openvino::{Core, DeviceType, ElementType, Shape, Tensor};
+use std::fs;
+
+#[test]
+fn memory_safety() -> anyhow::Result<()> {
+    let mut core = Core::new()?;
+    let xml = fs::read_to_string(Fixture::graph())?;
+    let weights = fs::read(Fixture::weights())?;
+
+    // Copy the fixture weights into a tensor. Once we're done here we want to get rid of the
+    // original weights buffer as a sanity check.
+    let shape = Shape::new(&[1, weights.len() as i64])?;
+    let mut weights_tensor = Tensor::new(ElementType::U8, &shape)?;
+    weights_tensor.get_raw_data_mut()?.copy_from_slice(&weights);
+    drop(weights);
+
+    // Now create a model from a reference to the weights tensor. We observed segfault crashes when
+    // passing weights by value but not by reference.
+    let model = core.read_model_from_buffer(xml.as_bytes(), Some(&weights_tensor))?;
+    drop(weights_tensor);
+
+    // Here we double-check that the model is usable. Though it has captured a reference to the
+    // `weights_tensor` and that tensor has been dropped, whatever OpenVINO is doing internally must
+    // be safe enough. See
+    // https://github.com/openvinotoolkit/openvino/blob/d840d86905f013d95cccbafaa0ddff266e250f75/src/inference/src/model_reader.cpp#L178.
+    assert_eq!(model.get_inputs_len()?, 1);
+    assert!(core.compile_model(&model, DeviceType::CPU).is_ok());
+    Ok(())
+}