mirror of https://github.com/python/cpython.git
78ffba4221
This should be a pure refactoring, without user-visible behaviour changes. Before this change, ctypes uses traditional native C types, usually identified by [`struct` format characters][struct-chars] when a short (and identifier-friendly) name is needed: - `signed char` (`b`) / `unsigned char` (`B`) - `short` (`h`) / `unsigned short` (`h`) - `int` (`i`) / `unsigned int` (`i`) - `long` (`l`) / `unsigned long` (`l`) - `long long` (`q`) / `unsigned long long` (`q`) These map to C99 fixed-width types, which this PR switches to: - - `int8_t`/`uint8_t` - `int16_t`/`uint16_t` - `int32_t`/`uint32_t` - `int64_t`/`uint64_t` The C standard doesn't guarantee that the “traditional” types must map to the fixints. But, [`ctypes` currently requires it][swapdefs], so the assumption won't break anything. By “map” I mean that the *size* of the types matches. The *alignment* requirements might not. This needs to be kept in mind but is not an issue in `ctypes` accessors, which [explicitly handle unaligned memory][memcpy] for the integer types. Note that there are 5 “traditional” C type sizes, but 4 fixed-width ones. Two of the former are functionally identical to one another; which ones they are is platform-specific (e.g. `int`==`long`==`int32_t`.) This means that one of the [current][current-impls-1] [implementations][current-impls-2] is redundant on any given platform. The fixint types are parametrized by the number of bytes/bits, and one bit for signedness. This makes it easier to autogenerate code for them or to write generic macros (though generic API like [`PyLong_AsNativeBytes`][PyLong_AsNativeBytes] is problematic for performance reasons -- especially compared to a `memcpy` with compile-time-constant size). When one has a *different* integer type, determining the corresponding fixint means a `sizeof` and signedness check. This is easier and more robust than the current implementations (see [`wchar_t`][sizeof-wchar_t] or [`_Bool`][sizeof-bool]). [swapdefs]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L420-L444 [struct-chars]: https://docs.python.org/3/library/struct.html#format-characters [current-impls-1]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L470-L653 [current-impls-2]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L703-L944 [memcpy]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L613 [PyLong_AsNativeBytes]: https://docs.python.org/3/c-api/long.html#c.PyLong_AsNativeBytes [sizeof-wchar_t]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L1547-L1555 [sizeof-bool]: https://github.com/python/cpython/blob/v3.13.0/Modules/_ctypes/cfield.c#L1562-L1572 Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com> |
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| .. | ||
| clinic | ||
| _ctypes.c | ||
| _ctypes_test.c | ||
| _ctypes_test.h | ||
| _ctypes_test_generated.c.h | ||
| callbacks.c | ||
| callproc.c | ||
| cfield.c | ||
| ctypes.h | ||
| malloc_closure.c | ||
| stgdict.c | ||