10000 bpo-45569: Change PYLONG_BITS_IN_DIGIT default to 30 (GH-30497) · python/cpython@025cbe7 · GitHub
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bpo-45569: Change PYLONG_BITS_IN_DIGIT default to 30 (GH-30497)
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‎Doc/using/configure.rst

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@@ -35,8 +35,7 @@ General Options
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Define the size in bits of Python :class:`int` digits: 15 or 30 bits.
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By default, the number of bits is selected depending on ``sizeof(void*)``:
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30 bits if ``void*`` size is 64-bit or larger, 15 bits otherwise.
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By default, the digit size is 30.
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Define the ``PYLONG_BITS_IN_DIGIT`` to ``15`` or ``30``.
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‎Doc/whatsnew/3.11.rst

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like Pyodide.
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(Contributed by Christian Heimes and Ethan Smith in :issue:`40280`.)
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* CPython will now use 30-bit digits by default for the Python :class:`int`
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implementation. Previously, the default was to use 30-bit digits on platforms
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with ``SIZEOF_VOID_P >= 8``, and 15-bit digits otherwise. It's still possible
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to explicitly request use of 15-bit digits via either the
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``--enable-big-digits`` option to the configure script or (for Windows) the
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``PYLONG_BITS_IN_DIGIT`` variable in ``PC/pyconfig.h``, but this option may
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be removed at some point in the future. (Contributed by Mark Dickinson in
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:issue:`45569`.)
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C API Changes
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=============
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‎Include/pyport.h

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@@ -85,20 +85,12 @@ Used in: Py_SAFE_DOWNCAST
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#define PY_INT32_T int32_t
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#define PY_INT64_T int64_t
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/* If PYLONG_BITS_IN_DIGIT is not defined then we'll use 30-bit digits if all
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the necessary integer types are available, and we're on a 64-bit platform
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(as determined by SIZEOF_VOID_P); otherwise we use 15-bit digits.
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From pyodide: WASM has 32 bit pointers but has native 64 bit arithmetic
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so it is more efficient to use 30 bit digits.
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/* PYLONG_BITS_IN_DIGIT describes the number of bits per "digit" (limb) in the
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* PyLongObject implementation (longintrepr.h). It's currently either 30 or 15,
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* defaulting to 30. The 15-bit digit option may be removed in the future.
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*/
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#ifndef PYLONG_BITS_IN_DIGIT
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#if SIZEOF_VOID_P >= 8 || defined(__wasm__)
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# define PYLONG_BITS_IN_DIGIT 30
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#else
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# define PYLONG_BITS_IN_DIGIT 15
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#endif
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#define PYLONG_BITS_IN_DIGIT 30
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#endif
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/* uintptr_t is the C9X name for an unsigned integral type such that a

‎Misc/NEWS.d/next/Build/2022-01-09-11-24-54.bpo-45569.zCIENy.rst

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The build now defaults to using 30-bit digits for Python integers. Previously
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either 15-bit or 30-bit digits would be selected, depending on the platform.
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15-bit digits may still be selected using the ``--enable-big-digits=15`` option
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to the ``configure`` script, or by defining ``PYLONG_BITS_IN_DIGIT`` in
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``pyconfig.h``.

‎configure

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@@ -1730,7 +1730,7 @@ Optional Features:
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Doc/library/socket.rst (default is yes if supported)
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--enable-big-digits[=15|30]
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use big digits (30 or 15 bits) for Python longs
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(default is system-dependent)]
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(default is 30)]
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--disable-test-modules don't build nor install test modules
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Optional Packages:

‎configure.ac

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@@ -5084,7 +5084,7 @@ AC_CHECK_DECLS([RTLD_LAZY, RTLD_NOW, RTLD_GLOBAL, RTLD_LOCAL, RTLD_NODELETE, RTL
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# determine what size digit to use for Python's longs
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AC_MSG_CHECKING([digit size for Python's longs])
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AC_ARG_ENABLE(big-digits,
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AS_HELP_STRING([--enable-big-digits@<:@=15|30@:>@],[use big digits (30 or 15 bits) for Python longs (default is system-dependent)]]),
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AS_HELP_STRING([--enable-big-digits@<:@=15|30@:>@],[use big digits (30 or 15 bits) for Python longs (default is 30)]]),
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[case $enable_big_digits in
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yes)
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enable_big_digits=30 ;;

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