python · skirpichev · May 13, 2025 · May 13, 2025 · May 13, 2025 · May 13, 2025
@@ -90,7 +90,7 @@ jobs:
     name: 'Check if generated files are up to date'
     # Don't use ubuntu-latest but a specific version to make the job
     # reproducible: to get the same tools versions (autoconf, aclocal, ...)
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-22.04
     timeout-minutes: 60
     needs: build-context
     if: needs.build-context.outputs.run-tests == 'true'
@@ -110,7 +110,9 @@ jobs:
           # Include env.pythonLocation in key to avoid changes in environment when setup-python updates Python
           key: ${{ github.job }}-${{ env.IMAGE_OS_VERSION }}-${{ needs.build-context.outputs.config-hash }}-${{ env.pythonLocation }}
       - name: Install dependencies
-        run: sudo ./.github/workflows/posix-deps-apt.sh
+        run: |
+          sudo ./.github/workflows/posix-deps-apt.sh
+          sudo apt-get -yq install libmpdec-dev
       - name: Add ccache to PATH
         run: echo "PATH=/usr/lib/ccache:$PATH" >> "$GITHUB_ENV"
       - name: Configure ccache action

diff --git a/Doc/deprecations/c-api-pending-removal-in-3.15.rst b/Doc/deprecations/c-api-pending-removal-in-3.15.rst
@@ -1,7 +1,6 @@
 Pending removal in Python 3.15
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-* The bundled copy of ``libmpdecimal``.
 * The :c:func:`!PyImport_ImportModuleNoBlock`:
   Use :c:func:`PyImport_ImportModule` instead.
 * :c:func:`PyWeakref_GetObject` and :c:func:`PyWeakref_GET_OBJECT`:

diff --git a/Doc/license.rst b/Doc/license.rst
@@ -975,39 +975,6 @@ on the cfuhash project::
    OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
-libmpdec
---------
-
-The :mod:`!_decimal` C extension underlying the :mod:`decimal` module
-is built using an included copy of the libmpdec
-library unless the build is configured ``--with-system-libmpdec``::
-
-   Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
-
-   Redistribution and use in source and binary forms, with or without
-   modification, are permitted provided that the following conditions
-   are met:
-
-   1. Redistributions of source code must retain the above copyright
-      notice, this list of conditions and the following disclaimer.
-
-   2. Redistributions in binary form must reproduce the above copyright
-      notice, this list of conditions and the following disclaimer in the
-      documentation and/or other materials provided with the distribution.
-
-   THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
-   ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-   ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
-   FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
-   OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
-   OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
-   SUCH DAMAGE.
-
-
 W3C C14N test suite
 -------------------
 

@@ -416,11 +416,6 @@ 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
 
@@ -835,22 +830,6 @@ 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.
-
-   .. deprecated-removed:: 3.13 3.15
-      A copy of the ``mpdecimal`` library sources will no longer be distributed
-      with Python 3.15.
-
-   .. seealso:: :option:`LIBMPDEC_CFLAGS` and :option:`LIBMPDEC_LIBS`.
-
 .. option:: --with-readline=readline|editline
 
    Designate a backend library for the :mod:`readline` module.

diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
@@ -2575,7 +2575,7 @@ 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`
   now defaults to ``yes``.
   The bundled copy of ``libmpdecimal`` will be removed in Python 3.15.
 

diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
@@ -154,6 +154,15 @@ that may require changes to your code.
 Build changes
 =============
 
+* Remove the bundled 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.
+
+  (Contributed by Sergey B Kirpichev in :gh:`115119`.)
+
+  .. _libmpdec: https://www.bytereef.org/mpdecimal/
+
 
 C API changes
 =============

@@ -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 "

@@ -225,7 +225,6 @@ RUNSHARED=       @RUNSHARED@
 ENSUREPIP=      @ENSUREPIP@
 
 # Internal static libraries
-LIBMPDEC_A= Modules/_decimal/libmpdec/libmpdec.a
 LIBEXPAT_A= Modules/expat/libexpat.a
 
 # HACL* build configuration
@@ -589,45 +588,6 @@ 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
 
@@ -945,7 +905,6 @@ 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' \
@@ -1409,60 +1368,6 @@ 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) $(CCSHARED)
@@ -3321,7 +3226,7 @@ MODULE_UNICODEDATA_DEPS=$(srcdir)/Modules/unicodedata_db.h $(srcdir)/Modules/uni
 MODULE__CTYPES_DEPS=$(srcdir)/Modules/_ctypes/ctypes.h
 MODULE__CTYPES_TEST_DEPS=$(srcdir)/Modules/_ctypes/_ctypes_test_generated.c.h
 MODULE__CTYPES_MALLOC_CLOSURE=@MODULE__CTYPES_MALLOC_CLOSURE@
-MODULE__DECIMAL_DEPS=$(srcdir)/Modules/_decimal/docstrings.h @LIBMPDEC_INTERNAL@
+MODULE__DECIMAL_DEPS=$(srcdir)/Modules/_decimal/docstrings.h
 MODULE__ELEMENTTREE_DEPS=$(srcdir)/Modules/pyexpat.c @LIBEXPAT_INTERNAL@
 MODULE__HASHLIB_DEPS=$(srcdir)/Modules/hashlib.h
 MODULE__IO_DEPS=$(srcdir)/Modules/_io/_iomodule.h

diff --git a/Misc/NEWS.d/3.12.0a2.rst b/Misc/NEWS.d/3.12.0a2.rst
@@ -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`.
 

diff --git a/Misc/NEWS.d/3.13.0b1.rst b/Misc/NEWS.d/3.13.0b1.rst
@@ -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.
 
@@ -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.
 
 ..
 

diff --git a/Misc/NEWS.d/next/Build/2025-05-13-12-38-26.gh-issue-115119.7n0nx3.rst b/Misc/NEWS.d/next/Build/2025-05-13-12-38-26.gh-issue-115119.7n0nx3.rst
@@ -0,0 +1,2 @@
+Removed bundled copy of the libmpdec, use system library if it's available.
+Patch by Sergey B Kirpichev.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Removed bundled copy of the libmpdec, use system library if it's available.
		Patch by Sergey B Kirpichev.