gh-115119: removed implicit fallback to the bundled libmpdec

.github/workflows/posix-deps-apt.sh

@@ -25,3 +25,10 @@ apt-get -yq install \
  uuid-dev \
  xvfb \
  zlib1g-dev
+
+# Workaround missing libmpdec-dev on ubuntu 24.04:
+# https://launchpad.net/~ondrej/+archive/ubuntu/php
+# https://deb.sury.org/
+sudo add-apt-repository ppa:ondrej/php
+apt-get update
+apt-get -yq install libmpdec-dev

Doc/whatsnew/3.15.rst

@@ -293,6 +293,11 @@ that may require changes to your code.
 Build changes
 =============
 
+* Removed implicit fallback to the bundled 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
 =============

Misc/NEWS.d/next/Build/2025-05-16-07-46-06.gh-issue-115119.ALBgS_.rst

@@ -0,0 +1,4 @@
+Removed implicit fallback to the bundled copy of the ``libmpdec`` library.
+Now this should be explicitly enabled via :option:`--with-system-libmpdec`
+set to ``no`` or :option:`!--without-system-libmpdec`. Patch by Sergey
+B Kirpichev.

configure.ac

@@ -4173,31 +4173,30 @@ 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([
@@ -4213,16 +4212,7 @@ 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;
- 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 to bundled libmpdecimal
- (deprecated and scheduled for removal in Python 3.15)])])
- USE_BUNDLED_LIBMPDEC()])
+ ])])
 
 # Disable forced inlining in debug builds, see GH-94847
 AS_VAR_IF(
@@ -8140,6 +8130,16 @@ PY_STDLIB_MOD([_curses_panel],
 PY_STDLIB_MOD([_decimal],
  [], [test "$have_mpdec" = "yes"],
  [$LIBMPDEC_CFLAGS], [$LIBMPDEC_LIBS])
+
+AS_VAR_IF([with_system_libmpdec], [no],
+ [AC_MSG_WARN([m4_normalize([
+ the bundled copy of libmpdecimal is scheduled for removal in Python 3.16;
+ consider using a system installed mpdecimal library.])])])
+AS_IF([test "$with_system_libmpdec" = "yes" && test "$have_mpdec" = "no"],
+ [AC_MSG_WARN([m4_normalize([
+ no system libmpdecimal found; falling back to pure-Python version
+ for the decimal module])])])
+
 PY_STDLIB_MOD([_dbm],
  [test -n "$with_dbmliborder"], [test "$have_dbm" != "no"],
  [$DBM_CFLAGS], [$DBM_LIBS])