Fix a tricky bug in Cython stream casting #904
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kingcrimsontianyu
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gforsyth
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rapidsai#893 contains a tricky bug. The following is incorrect: ```python def stream_register(stream: int, flags: int) -> None: cdef CUstream cpp_stream = <CUstream>stream ``` `stream` is a Python object. The cast applies to the address of this Python object, instead of the underlying integer value. This surprisingly does not trigger a compile error. There are two ways to fix this bug: - Method 1: double casting. The additional cast to `uintptr_t` extracts the underlying integer value of `stream` correctly. ```python def stream_register(stream: int, flags: int) -> None: cdef CUstream cpp_stream = <CUstream><uintptr_t>stream ``` - Method 2: `uintptr_t` as type hint (used in this PR). `uintptr_t` is not just a type hint; it actually causes `stream` to be a C object. ```python def stream_register(stream: uintptr_t, flags: int) -> None: cdef CUstream cpp_stream = <CUstream>stream ``` For both method, `uintptr_t` must be `cimport`-ed into the source file. Authors: - Tianyu Liu (https://github.com/kingcrimsontianyu) Approvers: - Lawrence Mitchell (https://github.com/wence-) URL: rapidsai#904
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#893 contains a tricky bug. The following is incorrect:
streamis a Python object. The cast applies to the address of this Python object, instead of the underlying integer value. This surprisingly does not trigger a compile error.There are two ways to fix this bug:
uintptr_textracts the underlying integer value ofstreamcorrectly.uintptr_tas type hint (used in this PR).uintptr_tis not just a type hint; it actually causesstreamto be a C object.For both method,
uintptr_tmust becimport-ed into the source file.