fix ownership of c stream error #4660
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wjones127
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viirya
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| match ffi_stream.get_last_error() { | ||
| Some(err_string) => err_string.as_ptr(), | ||
| None => std::ptr::null(), | ||
| } |
viirya
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Aug 7, 2023
| @@ -503,4 +512,32 @@ mod tests { | |||
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| _test_round_trip_import(vec![array.clone(), array.clone(), array]) | |||
| } | |||
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| #[test] | |||
| fn test_error_import() -> Result<()> { | |||
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Hmm, this test also passes in current branch without the fix. Doesn't?
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Yes that is true. We export an owned string, and then import an owned string. So round tripping to ourselves works. But other implementations (such as PyArrow) export a borrowed string, so our current implementation will raise a double free. To reproduce, within our implementation, add the changes for export at the top of the file, but leave out the changes for import. You should get a double free.
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I've added a PyArrow integration test that will fail on master.
viirya
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Which issue does this PR close?
Closes #4659.
Rationale for this change
The current implementation doesn't obey the ownership semantics laid out in the spec. When exporting to other Arrow implementations, it will leak memory through the
get_last_error()method. When importing from other Arrow implementations, it will cause a double free. Also, null pointers aren't being handled.What changes are included in this PR?
Changes
get_last_errorimplementations to treat the returned value as a borrowed and not owned string.Are there any user-facing changes?
I don't think so. It's possible that someone using the C Stream Interface to move data between an older version of arrow-rs and one after this change may face some FFI issues, but I doubt anyone is doing that.