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cuda.core: validate ctypes host callback signatures against CUhostFn - #2525
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Andy-Jost merged 5 commits intoAug 7, 2026
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Reject incompatible ctypes prototypes before CUDA sees them, document the required ABI, and note the stronger checking in the 1.2.0 release notes.
Use getattr for private ctypes calling-convention constants so the regenerated _host_callback.pyi type-checks cleanly.
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The previous check inspected ctypes' private _flags_ bits to identify the calling convention. That is wrong on Windows: CPython defines FUNCFLAG_STDCALL as 0, so a bitwise test can never match WINFUNCTYPE, and every win-64 test job rejected a valid callback. The 0x2 fallback used when _ctypes.FUNCFLAG_STDCALL is absent is FUNCFLAG_HRESULT, not stdcall. Drop the calling-convention check rather than repair the bit arithmetic. ctypes only honors stdcall when building a callback on 32-bit x86 Windows, which cuda.core does not support, and FUNCFLAG_PYTHONAPI is never consulted on the callback path, so CFUNCTYPE, WINFUNCTYPE, and PYFUNCTYPE all yield the same FFI_DEFAULT_ABI thunk. That leaves the declared result and argument types, which are reachable through the public restype/argtypes attributes. Reading those public attributes also lets a function pointer taken from a shared library be accepted once its restype and argtypes are declared, which the class-level lookup could never see.
…-host-callback # Conflicts: # cuda_core/docs/source/release/1.2.0-notes.rst
juenglin
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Summary
Closes#2439.
cuda.coreaccepted anyctypes._CFuncPtras a host callback and cast its address toCUhostFnwithout checking the declared prototype. CUDA requiresvoid (*)(void*); a mismatched restype, argument list, or calling convention is undefined behavior when the driver invokes the callback._resolve_host_callbacknow validates ctypes prototypes against that ABI before the pointer reaches CUDA. Construction (GraphNode.callback/GraphBuilder.callback) and update paths share the check. ValidCFUNCTYPE(None, c_void_p)callbacks keep working; on WindowsWINFUNCTYPEis also accepted. Docs, stubs, and the 1.2.0 release notes are updated accordingly.Changes
TypeError(message namesCUhostFnand suggests a conforming declaration or a Python callable)callback/updateAPIsWINFUNCTYPEaccept, skipped on Linux)cuda_core/docs/source/release/1.2.0-notes.rst