Jul 1, 2025 · May 14, 2025 · May 16, 2025 · May 16, 2025 · Jun 3, 2025 · Jun 3, 2025
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
    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'
          # 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/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
 Build changes
 =============

 * Removed implicit fallback to the buildled copy of the ``libmpdec`` library.
  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`.)


 C API changes
 =============
diff --git a/Misc/NEWS.d/next/Build/2025-05-16-07-46-06.gh-issue-115119.ALBgS_.rst b/Misc/NEWS.d/next/Build/2025-05-16-07-46-06.gh-issue-115119.ALBgS_.rst
 Removed implicit fallback to the buildled copy of the ``libmpdec`` library.
 Now this should be explicitly enabled with :option:`--with-system-libmpdec`
 set to ``no`` or with :option:`!--without-system-libmpdec`.  Patch by Sergey
 B Kirpichev.
diff --git a/configure b/configure
diff --git a/configure.ac b/configure.ac

 # Check for use of the system libmpdec library
 AC_MSG_CHECKING([for --with-system-libmpdec])
 AC_DEFUN([USE_BUNDLED_LIBMPDEC],
         [LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
          LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
          LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
          have_mpdec=yes
          with_system_libmpdec=no])
 AC_ARG_WITH(
  [system_libmpdec],
  [AS_HELP_STRING(
    [--with-system-libmpdec],
    [build _decimal module using an installed mpdecimal library, see Doc/library/decimal.rst (default is yes)]
  )],
  [],
  [AS_IF([test "x$with_system_libmpdec" = xno],
         [USE_BUNDLED_LIBMPDEC()])],
  [with_system_libmpdec="yes"])
 AC_MSG_RESULT([$with_system_libmpdec])

 AC_DEFUN([USE_BUNDLED_LIBMPDEC],
         [LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
          LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
          LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
          have_mpdec=yes
          with_system_libmpdec=no])

 AS_VAR_IF(
  [with_system_libmpdec], [yes],
  [PKG_CHECK_MODULES(
    [LIBMPDEC], [libmpdec >= 2.5.0], [],
    [LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
     LIBMPDEC_LIBS=${LIBMPDEC_LIBS-"-lmpdec -lm"}
     LIBMPDEC_INTERNAL=])],
  [USE_BUNDLED_LIBMPDEC()])
     LIBMPDEC_INTERNAL=])])

 AS_VAR_IF([with_system_libmpdec], [yes],
  [WITH_SAVE_ENV([
      ], [const char *x = mpd_version();])],
      [have_mpdec=yes],
      [have_mpdec=no])
  ])],
  [AC_MSG_WARN([m4_normalize([
     the bundled copy of libmpdecimal is scheduled for removal in Python 3.15;
  ])])
 AS_VAR_IF([with_system_libmpdec], [no],
          [AC_MSG_WARN([m4_normalize([
     the bundled copy of libmpdecimal is scheduled for removal in Python 3.16;
     consider using a system installed mpdecimal library.])])])

 AS_IF([test "$with_system_libmpdec" = "yes" && test "$have_mpdec" = "no"],
      [AC_MSG_WARN([m4_normalize([
         no system libmpdecimal found; falling back tobundled libmpdecimal
 (deprecated and scheduledforremoval in Python 3.15)])])
 USE_BUNDLED_LIBMPDEC()])
         no system libmpdecimal found; falling back topure-Python version
         forthe decimal module])])
 AS_VAR_SET([py_cv_module_]_decimal, [n/a])])

 # Disable forced inlining in debug builds, see GH-94847
 AS_VAR_IF(
Original file line number	Diff line number	Diff line change
Expand Up		@@ -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
skirpichev marked this conversation as resolved. Show resolvedHide resolved
		timeout-minutes: 60
		needs: build-context
		if: needs.build-context.outputs.run-tests == 'true'
Expand All		@@ -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
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -163,6 +163,11 @@ that may require changes to your code.
		Build changes
		=============

		* Removed implicit fallback to the buildled copy of the ``libmpdec`` library.
skirpichev marked this conversation as resolved. Show resolvedHide resolved
		Now this should be explicitly enabled with :option:`--with-system-libmpdec`
		set to ``no`` or with :option:`!--without-system-libmpdec`.
Copy link Member hugovkJul 2, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Does the devguide need updating? For example the macOS build instructions say to use`--with-system-libmpdec`, do we want people to stop using that for 3.15+? https://devguide.python.org/getting-started/setup-building/#install-dependencies Copy link ContributorAuthor skirpichevJul 2, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. I think we can just drop this option. It's specified in 3.13+ instructions (where it's default to "yes"). I'll prepare a patch.
		(Contributed by Sergey B Kirpichev in :gh:`115119`.)


		C API changes
		=============
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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,4 @@
		Removed implicit fallback to the buildled copy of the ``libmpdec`` library.
skirpichev marked this conversation as resolved. Show resolvedHide resolved
		Now this should be explicitly enabled with :option:`--with-system-libmpdec`
		set to ``no`` or with :option:`!--without-system-libmpdec`. Patch by Sergey
skirpichev marked this conversation as resolved. Show resolvedHide resolved
		B Kirpichev.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -4092,31 +4092,30 @@ fi

		# Check for use of the system libmpdec library
		AC_MSG_CHECKING([for --with-system-libmpdec])
		AC_DEFUN([USE_BUNDLED_LIBMPDEC],
		[LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
		LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
		LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
		have_mpdec=yes
		with_system_libmpdec=no])
		AC_ARG_WITH(
		[system_libmpdec],
		[AS_HELP_STRING(
		[--with-system-libmpdec],
		[build _decimal module using an installed mpdecimal library, see Doc/library/decimal.rst (default is yes)]
		)],
		[],
		[AS_IF([test "x$with_system_libmpdec" = xno],
		[USE_BUNDLED_LIBMPDEC()])],
		[with_system_libmpdec="yes"])
		AC_MSG_RESULT([$with_system_libmpdec])

		AC_DEFUN([USE_BUNDLED_LIBMPDEC],
		[LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
		LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
		LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
		have_mpdec=yes
		with_system_libmpdec=no])

		AS_VAR_IF(
		[with_system_libmpdec], [yes],
		[PKG_CHECK_MODULES(
		[LIBMPDEC], [libmpdec >= 2.5.0], [],
		[LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
		LIBMPDEC_LIBS=${LIBMPDEC_LIBS-"-lmpdec -lm"}
		LIBMPDEC_INTERNAL=])],
		[USE_BUNDLED_LIBMPDEC()])
		LIBMPDEC_INTERNAL=])])

		AS_VAR_IF([with_system_libmpdec], [yes],
		[WITH_SAVE_ENV([
Expand All		@@ -4132,16 +4131,17 @@ AS_VAR_IF([with_system_libmpdec], [yes],
		], [const char *x = mpd_version();])],
		[have_mpdec=yes],
		[have_mpdec=no])
		])],
		[AC_MSG_WARN([m4_normalize([
		the bundled copy of libmpdecimal is scheduled for removal in Python 3.15;
		])])
		AS_VAR_IF([with_system_libmpdec], [no],
		[AC_MSG_WARN([m4_normalize([
		the bundled copy of libmpdecimal is scheduled for removal in Python 3.16;
		consider using a system installed mpdecimal library.])])])

		AS_IF([test "$with_system_libmpdec" = "yes" && test "$have_mpdec" = "no"],
		[AC_MSG_WARN([m4_normalize([
		no system libmpdecimal found; falling back tobundled libmpdecimal
		(deprecated and scheduledforremoval in Python 3.15)])])
		USE_BUNDLED_LIBMPDEC()])
		no system libmpdecimal found; falling back topure-Python version
		forthe decimal module])])
		AS_VAR_SET([py_cv_module_]_decimal, [n/a])])
Copy link Member AA-TurnerMay 16, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. `AC_MSG_ERROR`? I think opting in to the pure Python version should be explicit. Copy link ContributorAuthor skirpichevMay 16, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. AC_MSG_ERROR ? Well, that could be an option. Though, more complex wrt implementation: all linux jobs will fail, unless we either provide system libmpdec or change ./configure invocations to use a new option. I think opting in to the pure Python version should be explicit. I'm not sure it's useful. After all, the pure-Python version is always available as the`_pydecimal.py`. Did you suggest a new option like`--with-purepython-decimal`? Copy link Member picnixzJun 2, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. A warning is actually ok, but users may not see it and then, they would have a slow version of decimal. OTOH, an error might be too abrupt but at least the tansition would be more explicit and would force people to upgrade if they want an efficient way to do it. I'm +0.25 for AC_MSG_ERROR just to force people to update. We can add an option`--allow-fallback-to-pydecimal` to handle CI possible failures, though this means that devs should be aware that their C code might not be tested in the CI due to that.

		# Disable forced inlining in debug builds, see GH-94847
		AS_VAR_IF(
Expand Down