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Merged
zware merged 38 commits into from
May 12, 2026
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gh-115119: Removed bundled copy of the libmpdec #133964

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c8b8a57
gh-115119: Removed bundled copy of the libmpdec
skirpichev May 13, 2025
43c8721
+ configure
skirpichev May 13, 2025
9d6c9b5
+1
skirpichev May 13, 2025
5de2aa2
Apply suggestions from code review
skirpichev May 13, 2025
dfd9f40
+ configure
skirpichev May 13, 2025
769a36a
autoconf
AA-Turner May 13, 2025
60f7ae2
revert
AA-Turner May 13, 2025
b9af863
makesetup
AA-Turner May 13, 2025
81c7020
+ lint and macos
skirpichev May 13, 2025
3bf12e8
Windows: SBOM
AA-Turner May 13, 2025
4555447
lint
AA-Turner May 13, 2025
2fca0e5
fix docs
skirpichev May 14, 2025
800dd01
XXX disable _decimal if no libmpdec is available
skirpichev May 14, 2025
be3d413
+1
skirpichev May 14, 2025
bd03679
fix json
skirpichev May 14, 2025
2ba6b8b
reorder
skirpichev May 14, 2025
8bc2e53
install libmpdec on this job
skirpichev May 14, 2025
a79e284
Merge branch 'main' into remove-bundled-mpdecimal/115119
skirpichev Jun 3, 2025
f0dc0bb
XXX try libmpdec-dev from PPA for PHP: https://launchpad.net/~ondrej/…
skirpichev Jun 3, 2025
6e74feb
+1
skirpichev Jun 3, 2025
a4a6796
Merge branch 'master' into remove-bundled-mpdecimal/115119
skirpichev May 8, 2026
e0bdb87
news
skirpichev May 8, 2026
adf7af4
+1
skirpichev May 8, 2026
9ccd488
+1
skirpichev May 8, 2026
e10ed83
Apply suggestions from code review
skirpichev May 9, 2026
b2f5f30
address review: restore license.rst
skirpichev May 9, 2026
081d1e0
address review: revert unrelated change
skirpichev May 9, 2026
97767d6
address review: cleanup configure.ac
skirpichev May 9, 2026
57bd0b0
Merge branch 'main' into remove-bundled-mpdecimal/115119
skirpichev May 11, 2026
fa0d506
Merge branch 'master' into remove-bundled-mpdecimal/115119
skirpichev May 12, 2026
0cab465
address review: move news
skirpichev May 12, 2026
f4a1b18
address review: trying to reword license.rst
skirpichev May 12, 2026
11867cd
address review: cleanup Modules/_decimal/README.txt
skirpichev May 12, 2026
0e3afd7
address review: set module missing, if have_mpdec==no
skirpichev May 12, 2026
0dd4a29
Apply suggestions from code review
skirpichev May 12, 2026
59a7986
address review: configure.ac cleanup
skirpichev May 12, 2026
c1e262a
Merge branch 'master' into remove-bundled-mpdecimal/115119
skirpichev May 12, 2026
b4cc60d
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zware May 12, 2026
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2 changes: 1 addition & 1 deletion .github/workflows/posix-deps-apt.sh
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Expand Up @@ -27,7 +27,7 @@ apt-get -yq --no-install-recommends install \
zlib1g-dev

# Workaround missing libmpdec-dev on ubuntu 24.04 by building mpdecimal
# from source. ppa:ondrej/php (launchpad.net) are unreliable
# from source. ppa:ondrej/php (launchpad.net) are unreliable
# (https://status.canonical.com) so fetch the tarball directly
# from the upstream host.
# https://www.bytereef.org/mpdecimal/
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4 changes: 2 additions & 2 deletions Doc/license.rst
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Expand Up @@ -959,8 +959,8 @@ on the cfuhash project::
libmpdec
Comment thread
skirpichev marked this conversation as resolved.
--------

The :mod:`!_decimal` C extension underlying the :mod:`decimal` module
is built using an included copy of the libmpdec
Previously, the :mod:`!_decimal` C extension underlying the :mod:`decimal` module
was built using an included copy of the libmpdec
Comment thread
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Outdated
library unless the build is configured ``--with-system-libmpdec``::
Comment thread
skirpichev marked this conversation as resolved.

@zware zware May 12, 2026

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Wouldn't hurt to fix the libffi section as well. Suggested wording here, though:

Suggested change
Previously, the :mod:`!_decimal` C extension underlying the :mod:`decimal` module
was built using an included copy of the libmpdec
library unless the build is configured ``--with-system-libmpdec``::
The :mod:`!_decimal` C extension underlying the :mod:`decimal` module
is linked to the libmpdec C library::

On the other hand, we could just leave this file alone for now and get someone more knowledgeable about such things to tell us what we should do in a separate issue :)

@skirpichev skirpichev May 12, 2026

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Then lets keep this intact.


Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
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5 changes: 4 additions & 1 deletion Doc/tools/removed-ids.txt
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Expand Up @@ -6,6 +6,9 @@ c-api/file.html: deprecated-api

library/asyncio-task.html: terminating-a-task-group

# Removed libmpdec
using/configure.html: cmdoption-with-system-libmpdec
Comment thread
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# Removed APIs
library/symtable.html: symtable.Class.get_methods
library/sys.html: sys._enablelegacywindowsfsencoding
library/sys.html: sys._enablelegacywindowsfsencoding
29 changes: 0 additions & 29 deletions Doc/using/configure.rst
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Expand Up @@ -112,7 +112,6 @@ Dependencies to build optional modules are:

.. [1] If *libmpdec* is not available, the :mod:`decimal` module will use
a pure-Python implementation.
See :option:`--with-system-libmpdec` for details.
.. [2] See :option:`--with-readline` for choosing the backend for the
:mod:`readline` module.
.. [3] The :mod:`uuid` module uses ``_uuid`` to generate "safe" UUIDs.
Expand Down Expand Up @@ -553,11 +552,6 @@ Options for third-party dependencies
C compiler and linker flags for ``libmpdec``, used by :mod:`decimal` module,
overriding ``pkg-config``.

.. note::

These environment variables have no effect unless
:option:`--with-system-libmpdec` is specified.

.. option:: LIBLZMA_CFLAGS
.. option:: LIBLZMA_LIBS

Expand Down Expand Up @@ -1067,29 +1061,6 @@ Libraries options
Build the :mod:`!pyexpat` module using an installed ``expat`` library
(default is no).

.. option:: --with-system-libmpdec

Build the ``_decimal`` extension module using an installed ``mpdecimal``
library, see the :mod:`decimal` module (default is yes).

.. versionadded:: 3.3

.. versionchanged:: 3.13
Default to using the installed ``mpdecimal`` library.

.. versionchanged:: 3.15

A bundled copy of the library will no longer be selected
implicitly if an installed ``mpdecimal`` library is not found.
In Python 3.15 only, it can still be selected explicitly using
``--with-system-libmpdec=no`` or ``--without-system-libmpdec``.

.. deprecated-removed:: 3.13 3.16
A copy of the ``mpdecimal`` library sources will no longer be distributed
with Python 3.16.

.. seealso:: :option:`LIBMPDEC_CFLAGS` and :option:`LIBMPDEC_LIBS`.

.. option:: --with-readline=readline|editline

Designate a backend library for the :mod:`readline` module.
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2 changes: 1 addition & 1 deletion Doc/whatsnew/3.13.rst
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Expand Up @@ -2597,7 +2597,7 @@ Build Changes

.. _mimalloc library: https://github.com/microsoft/mimalloc/

* The :file:`configure` option :option:`--with-system-libmpdec`
* The :file:`configure` option :option:!--with-system-libmpdec`
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Outdated
now defaults to ``yes``.
The bundled copy of ``libmpdec`` will be removed in Python 3.16.

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2 changes: 1 addition & 1 deletion Doc/whatsnew/3.15.rst
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Expand Up @@ -2626,7 +2626,7 @@ Build changes
=============

* Removed implicit fallback to the bundled copy of the ``libmpdec`` library.
Now this should be explicitly enabled with :option:`--with-system-libmpdec`
Now this should be explicitly enabled with :option:`!--with-system-libmpdec`
set to ``no`` or with :option:`!--without-system-libmpdec`.
(Contributed by Sergey B Kirpichev in :gh:`115119`.)

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11 changes: 11 additions & 0 deletions Doc/whatsnew/3.16.rst
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Expand Up @@ -191,6 +191,17 @@ that may require changes to your code.
Build changes
=============

* Remove the bundled copy of the libmpdec_ decimal library from the CPython source tree
to simplify maintenence and updates. The :mod:`decimal` module will now
unconditionally use the system's libmpdec decimal library. Also remove the
now unused :option:`!--with-system-libmpdec` :program:`configure` flag.
Comment thread
skirpichev marked this conversation as resolved.
This change has no impact on binary releases of Python, which have been
built against a separate copy of libmpdec for the past several releases.

(Contributed by Sergey B Kirpichev in :gh:`115119`.)

.. _libmpdec: https://www.bytereef.org/mpdecimal/


C API changes
=============
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1 change: 0 additions & 1 deletion Mac/BuildScript/build-installer.py
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Expand Up @@ -1158,7 +1158,6 @@ def buildPython():
print(" NOTE: --with-mimalloc=no pending resolution of weak linking issues")
runCommand("%s -C --enable-framework --enable-universalsdk=/ "
"--with-mimalloc=no "
"--with-system-libmpdec "
"--with-universal-archs=%s "
"%s "
"%s "
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96 changes: 0 additions & 96 deletions Makefile.pre.in
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Expand Up @@ -231,7 +231,6 @@ RUNSHARED= @RUNSHARED@
ENSUREPIP= @ENSUREPIP@

# Internal static libraries
LIBMPDEC_A= Modules/_decimal/libmpdec/libmpdec.a
LIBEXPAT_A= Modules/expat/libexpat.a

# HACL* build configuration
Expand Down Expand Up @@ -606,45 +605,6 @@ LINK_PYTHON_OBJS=@LINK_PYTHON_OBJS@
DTRACE_DEPS = \
Python/ceval.o Python/gc.o Python/import.o Python/sysmodule.o

##########################################################################
# decimal's libmpdec

LIBMPDEC_OBJS= \
Modules/_decimal/libmpdec/basearith.o \
Modules/_decimal/libmpdec/constants.o \
Modules/_decimal/libmpdec/context.o \
Modules/_decimal/libmpdec/convolute.o \
Modules/_decimal/libmpdec/crt.o \
Modules/_decimal/libmpdec/difradix2.o \
Modules/_decimal/libmpdec/fnt.o \
Modules/_decimal/libmpdec/fourstep.o \
Modules/_decimal/libmpdec/io.o \
Modules/_decimal/libmpdec/mpalloc.o \
Modules/_decimal/libmpdec/mpdecimal.o \
Modules/_decimal/libmpdec/numbertheory.o \
Modules/_decimal/libmpdec/sixstep.o \
Modules/_decimal/libmpdec/transpose.o
# _decimal does not use signaling API
# Modules/_decimal/libmpdec/mpsignal.o

LIBMPDEC_HEADERS= \
$(srcdir)/Modules/_decimal/libmpdec/basearith.h \
$(srcdir)/Modules/_decimal/libmpdec/bits.h \
$(srcdir)/Modules/_decimal/libmpdec/constants.h \
$(srcdir)/Modules/_decimal/libmpdec/convolute.h \
$(srcdir)/Modules/_decimal/libmpdec/crt.h \
$(srcdir)/Modules/_decimal/libmpdec/difradix2.h \
$(srcdir)/Modules/_decimal/libmpdec/fnt.h \
$(srcdir)/Modules/_decimal/libmpdec/fourstep.h \
$(srcdir)/Modules/_decimal/libmpdec/io.h \
$(srcdir)/Modules/_decimal/libmpdec/mpalloc.h \
$(srcdir)/Modules/_decimal/libmpdec/mpdecimal.h \
$(srcdir)/Modules/_decimal/libmpdec/numbertheory.h \
$(srcdir)/Modules/_decimal/libmpdec/sixstep.h \
$(srcdir)/Modules/_decimal/libmpdec/transpose.h \
$(srcdir)/Modules/_decimal/libmpdec/typearith.h \
$(srcdir)/Modules/_decimal/libmpdec/umodarith.h

##########################################################################
# pyexpat's expat library

Expand Down Expand Up @@ -962,7 +922,6 @@ coverage-lcov:
@lcov $(COVERAGE_LCOV_OPTIONS) --remove $(COVERAGE_INFO) \
'*/Modules/_hacl/*' \
'*/Modules/_ctypes/libffi*/*' \
'*/Modules/_decimal/libmpdec/*' \
'*/Modules/expat/*' \
'*/Modules/xx*.c' \
'*/Python/pyfpe.c' \
Expand Down Expand Up @@ -1471,60 +1430,6 @@ PYTHON_HEADERS= \
\
$(srcdir)/Python/stdlib_module_names.h

##########################################################################
# Build static libmpdec.a
LIBMPDEC_CFLAGS=@LIBMPDEC_CFLAGS@ $(PY_STDMODULE_CFLAGS) $(CCSHARED)

# "%.o: %c" is not portable
Modules/_decimal/libmpdec/basearith.o: $(srcdir)/Modules/_decimal/libmpdec/basearith.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/basearith.c

Modules/_decimal/libmpdec/constants.o: $(srcdir)/Modules/_decimal/libmpdec/constants.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/constants.c

Modules/_decimal/libmpdec/context.o: $(srcdir)/Modules/_decimal/libmpdec/context.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/context.c

Modules/_decimal/libmpdec/convolute.o: $(srcdir)/Modules/_decimal/libmpdec/convolute.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/convolute.c

Modules/_decimal/libmpdec/crt.o: $(srcdir)/Modules/_decimal/libmpdec/crt.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/crt.c

Modules/_decimal/libmpdec/difradix2.o: $(srcdir)/Modules/_decimal/libmpdec/difradix2.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/difradix2.c

Modules/_decimal/libmpdec/fnt.o: $(srcdir)/Modules/_decimal/libmpdec/fnt.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/fnt.c

Modules/_decimal/libmpdec/fourstep.o: $(srcdir)/Modules/_decimal/libmpdec/fourstep.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/fourstep.c

Modules/_decimal/libmpdec/io.o: $(srcdir)/Modules/_decimal/libmpdec/io.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/io.c

Modules/_decimal/libmpdec/mpalloc.o: $(srcdir)/Modules/_decimal/libmpdec/mpalloc.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/mpalloc.c

Modules/_decimal/libmpdec/mpdecimal.o: $(srcdir)/Modules/_decimal/libmpdec/mpdecimal.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/mpdecimal.c

Modules/_decimal/libmpdec/mpsignal.o: $(srcdir)/Modules/_decimal/libmpdec/mpsignal.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/mpsignal.c

Modules/_decimal/libmpdec/numbertheory.o: $(srcdir)/Modules/_decimal/libmpdec/numbertheory.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/numbertheory.c

Modules/_decimal/libmpdec/sixstep.o: $(srcdir)/Modules/_decimal/libmpdec/sixstep.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/sixstep.c

Modules/_decimal/libmpdec/transpose.o: $(srcdir)/Modules/_decimal/libmpdec/transpose.c $(LIBMPDEC_HEADERS) $(PYTHON_HEADERS)
$(CC) -c $(LIBMPDEC_CFLAGS) -o $@ $(srcdir)/Modules/_decimal/libmpdec/transpose.c

$(LIBMPDEC_A): $(LIBMPDEC_OBJS)
-rm -f $@
$(AR) $(ARFLAGS) $@ $(LIBMPDEC_OBJS)

##########################################################################
# Build static libexpat.a
LIBEXPAT_CFLAGS=@LIBEXPAT_CFLAGS@ $(PY_STDMODULE_CFLAGS) $(CCSHARED)
Expand Down Expand Up @@ -3501,7 +3406,6 @@ MODULE_UNICODEDATA_DEPS=$(srcdir)/Modules/unicodedata_db.h $(srcdir)/Modules/uni
MODULE__CTYPES_DEPS=$(srcdir)/Modules/_ctypes/ctypes.h
MODULE__CTYPES_TEST_DEPS=$(srcdir)/Modules/_ctypes/_ctypes_test_generated.c.h
MODULE__CTYPES_MALLOC_CLOSURE=@MODULE__CTYPES_MALLOC_CLOSURE@
MODULE__DECIMAL_DEPS=@LIBMPDEC_INTERNAL@
MODULE__ELEMENTTREE_DEPS=$(srcdir)/Modules/pyexpat.c @LIBEXPAT_INTERNAL@
MODULE__HASHLIB_DEPS=$(srcdir)/Modules/hashlib.h
MODULE__IO_DEPS=$(srcdir)/Modules/_io/_iomodule.h
Expand Down
2 changes: 1 addition & 1 deletion Misc/NEWS.d/3.12.0a2.rst
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Expand Up @@ -957,7 +957,7 @@ Fix ``make regen-test-levenshtein`` for out-of-tree builds.
.. nonce: eVXGEx
.. section: Build

Don't use vendored ``libmpdec`` headers if :option:`--with-system-libmpdec`
Don't use vendored ``libmpdec`` headers if :option:`!--with-system-libmpdec`
is passed to :program:`configure`. Don't use vendored ``libexpat`` headers
if :option:`--with-system-expat` is passed to :program:`configure`.

Expand Down
4 changes: 2 additions & 2 deletions Misc/NEWS.d/3.13.0b1.rst
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Expand Up @@ -1429,7 +1429,7 @@ script) without specifying a value for ``UseTIER2``.
.. nonce: LT27pF
.. section: Build

The :file:`configure` option :option:`--with-system-libmpdec` now defaults
The :file:`configure` option :option:`!--with-system-libmpdec` now defaults
to ``yes``. The bundled copy of ``libmpdecimal`` will be removed in Python
3.15.

Expand Down Expand Up @@ -1470,7 +1470,7 @@ Increase WASI stack size from 512 KiB to 8 MiB and the initial memory from
.. section: Build

:program:`configure` now uses :program:`pkg-config` to detect :mod:`decimal`
dependencies if the :option:`--with-system-libmpdec` option is given.
dependencies if the :option:`!--with-system-libmpdec` option is given.

..

Expand Down
2 changes: 1 addition & 1 deletion Misc/NEWS.d/3.15.0a1.rst
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Expand Up @@ -6395,7 +6395,7 @@ Add support for configuring compiler flags for the JIT with ``CFLAGS_JIT``
.. section: Build

Removed implicit fallback to the bundled copy of the ``libmpdec`` library.
Now this should be explicitly enabled via :option:`--with-system-libmpdec`
Now this should be explicitly enabled via :option:`!--with-system-libmpdec`
set to ``no`` or :option:`!--without-system-libmpdec`. Patch by Sergey B
Kirpichev.

Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Build/2025-05-13-12-38-26.gh-issue-115119.7n0nx3.rst
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@@ -0,0 +1,2 @@
Removed bundled copy of the libmpdec, use system library if it's available.
Patch by Sergey B Kirpichev.
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