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| -rw-r--r-- | Doc/library/ctypes.rst | 20 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Documentation/2022-11-16-12-52-23.gh-issue-92892.TS-P0j.rst | 1 |
2 files changed, 21 insertions, 0 deletions
diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst index e85a6cb..71e5545 100644 --- a/Doc/library/ctypes.rst +++ b/Doc/library/ctypes.rst @@ -373,6 +373,26 @@ that they can be converted to the required C data type:: 31 >>> +.. _ctypes-calling-variadic-functions: + +Calling varadic functions +^^^^^^^^^^^^^^^^^^^^^^^^^ + +On a lot of platforms calling variadic functions through ctypes is exactly the same +as calling functions with a fixed number of parameters. On some platforms, and in +particular ARM64 for Apple Platforms, the calling convention for variadic functions +is different than that for regular functions. + +On those platforms it is required to specify the *argtypes* attribute for the +regular, non-variadic, function arguments: + +.. code-block:: python3 + + libc.printf.argtypes = [ctypes.c_char_p] + +Because specifying the attribute does inhibit portability it is adviced to always +specify ``argtypes`` for all variadic functions. + .. _ctypes-calling-functions-with-own-custom-data-types: diff --git a/Misc/NEWS.d/next/Documentation/2022-11-16-12-52-23.gh-issue-92892.TS-P0j.rst b/Misc/NEWS.d/next/Documentation/2022-11-16-12-52-23.gh-issue-92892.TS-P0j.rst new file mode 100644 index 0000000..54e421d --- /dev/null +++ b/Misc/NEWS.d/next/Documentation/2022-11-16-12-52-23.gh-issue-92892.TS-P0j.rst @@ -0,0 +1 @@ +Document that calling variadic functions with ctypes requires special care on macOS/arm64 (and possibly other platforms). |