sunchao commented on a change in pull request #1449:
URL: https://github.com/apache/arrow-rs/pull/1449#discussion_r827605292
##########
File path: arrow/src/ffi.rs
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@@ -781,11 +781,19 @@ impl ArrowArray {
.to_string(),
));
};
- let ffi_array = (*array).clone();
- let ffi_schema = (*schema).clone();
+
+ let array_mut = array as *mut FFI_ArrowArray;
+ let schema_mut = schema as *mut FFI_ArrowSchema;
+
+ let array_data = std::ptr::replace(array_mut, FFI_ArrowArray::empty());
Review comment:
Actually after thinking more on this, it seems this won't address the
original problem neither. It basically just calls `drop` on `FFI_ArrowArray`
(which is empty), but doesn't free the memory pointed by `array` and `schema`.
```
+-------+
| array |
+-------+ +----------------------------+
| | |
+----------------->| FFI_ArrowArray | <- memory leaked
| |
+----------------------------+
```
For instance, if `array` and `schema` are from `Arc::into_raw`, then the
memory allocated for the `Arc` will become dangling after this, and thus memory
leak.
I'm thinking whether we'll need two APIs, one where we are able to take the
ownership of the memory allocated for the `array` and `schema` (e.g., exported
by `Arc::into_raw` from Rust itself), and one where we cannot take the
ownership (e.g., memory was allocated by other languages such as Java), and
thus requires the exporter to free the memory by itself later.
For the latter, we can clone the content for `FFI_ArrowArray` and
`FFI_ArrowSchema`, and set the content of the original `array` and `schema` to
be `FFI_ArrowArray::empty()` and `FFI_ArrowSchema::empty()` so that the
exporter can just safely free the memory later.
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