[GitHub] [arrow] hu6360567 commented on issue #11846: Crash when import/export between C++ and Rust

[GitBox <gi...@apache.org>]

hu6360567 commented on issue #11846:
URL: https://github.com/apache/arrow/issues/11846#issuecomment-985286141


   I've figured out the key problem, I missed up rust/C++ mangaged FFI pointers.
   In `import_array`,  it consumes the C++ managed pointers.
   
   As https://github.com/apache/arrow-rs/issues/994#issuecomment-985254643 mentioned, when calling `arrow::ExportRecordBatch`, the output pointers should be created in rust.
   
   Fix patch as below,
   ```rust
   #[no_mangle]
   pub extern "C" fn create_array(content: *mut *const FFI_ArrowArray, schema: *mut *const FFI_ArrowSchema) {
       unsafe {
           let array = ArrowArray::empty();
           let (c, s) = ArrowArray::into_raw(array);
           *content = c;
           *schema = s;
       }
   }
   ```
   
   ```c++
   void test2() {
       auto property = generateRB();
       const ArrowArray *array = nullptr;
       const ArrowSchema *schema = nullptr;
       create_array(&array, &schema);
       printf("array@%p, schema@%p\n", array, schema);
       DEBUG_C_INTERFACE("TEST2 Before Export", array, schema);
       std::cout << property->column_data(0).use_count() << "," << property->column_data(1).use_count() << std::endl;
       arrow::ExportRecordBatch(*property, const_cast<ArrowArray *>(array), const_cast<ArrowSchema *>(schema));
       DEBUG_C_INTERFACE("TEST2 After Export", array, schema);
       std::cout << property->column_data(0).use_count() << "," << property->column_data(1).use_count() << std::endl;
   
       DEBUG_C_INTERFACE("TEST2 Before Import", array, schema);
       std::cout << property->column_data(0).use_count() << "," << property->column_data(1).use_count() << std::endl;
       import_array(array, schema);
       DEBUG_C_INTERFACE("TEST2 After Import", array, schema);
       std::cout << property->column_data(0).use_count() << "," << property->column_data(1).use_count() << std::endl;
   }
   ```


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