From cff99f36f06688063a126c370cf3ab88dc7244d2 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Tue, 13 Feb 2024 15:22:41 +0100
Subject: [PATCH 1/4] gh-115119: Detect _decimal dependencies using pkg-config

Only libmpdec 4.0.0 supports pkg-config.
---
 Modules/_decimal/_decimal.c |  10 ++-
 configure                   | 159 ++++++++++++++++++++++++++----------
 configure.ac                | 127 ++++++++++++++--------------
 3 files changed, 192 insertions(+), 104 deletions(-)

diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
index 5b053c73e20bc9..68d5229f271892 100644
--- a/Modules/_decimal/_decimal.c
+++ b/Modules/_decimal/_decimal.c
@@ -33,7 +33,15 @@
 #include "pycore_long.h"          // _PyLong_IsZero()
 #include "pycore_pystate.h"       // _PyThreadState_GET()
 #include "complexobject.h"
-#include "mpdecimal.h"
+
+#include <mpdecimal.h>
+
+// Reuse config from mpdecimal.h if present.
+#if defined(MPD_CONFIG_64)
+  #define CONFIG_64 MPD_CONFIG_64
+#elif defined(MPD_CONFIG_32)
+  #define CONFIG_32 MPD_CONFIG_32
+#endif
 
 #include <ctype.h>                // isascii()
 #include <stdlib.h>
diff --git a/configure b/configure
index ba2d49df7c65fe..fe447a13db0d27 100755
--- a/configure
+++ b/configure
@@ -873,6 +873,7 @@ TCLTK_CFLAGS
 LIBSQLITE3_LIBS
 LIBSQLITE3_CFLAGS
 LIBMPDEC_INTERNAL
+LIBMPDEC_LIBS
 LIBMPDEC_CFLAGS
 MODULE__CTYPES_MALLOC_CLOSURE
 LIBFFI_LIBS
@@ -1140,6 +1141,8 @@ LIBUUID_CFLAGS
 LIBUUID_LIBS
 LIBFFI_CFLAGS
 LIBFFI_LIBS
+LIBMPDEC_CFLAGS
+LIBMPDEC_LIBS
 LIBSQLITE3_CFLAGS
 LIBSQLITE3_LIBS
 TCLTK_CFLAGS
@@ -1961,6 +1964,10 @@ Some influential environment variables:
   LIBFFI_CFLAGS
               C compiler flags for LIBFFI, overriding pkg-config
   LIBFFI_LIBS linker flags for LIBFFI, overriding pkg-config
+  LIBMPDEC_CFLAGS
+              C compiler flags for LIBMPDEC, overriding pkg-config
+  LIBMPDEC_LIBS
+              linker flags for LIBMPDEC, overriding pkg-config
   LIBSQLITE3_CFLAGS
               C compiler flags for LIBSQLITE3, overriding pkg-config
   LIBSQLITE3_LIBS
@@ -14416,27 +14423,91 @@ printf "%s\n" "$with_system_libmpdec" >&6; }
 if test "x$with_system_libmpdec" = xyes
 then :
 
-  LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
-  LIBMPDEC_LDFLAGS=${LIBMPDEC_LDFLAGS-"-lmpdec"}
-  LIBMPDEC_INTERNAL=
-
-else $as_nop
+pkg_failed=no
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for libmpdec" >&5
+printf %s "checking for libmpdec... " >&6; }
 
-  LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
-  LIBMPDEC_LDFLAGS="-lm \$(LIBMPDEC_A)"
-  LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
+if test -n "$LIBMPDEC_CFLAGS"; then
+    pkg_cv_LIBMPDEC_CFLAGS="$LIBMPDEC_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmpdec\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libmpdec") 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LIBMPDEC_CFLAGS=`$PKG_CONFIG --cflags "libmpdec" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LIBMPDEC_LIBS"; then
+    pkg_cv_LIBMPDEC_LIBS="$LIBMPDEC_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmpdec\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libmpdec") 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LIBMPDEC_LIBS=`$PKG_CONFIG --libs "libmpdec" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
 
-    if test "x$with_pydebug" = xyes
-then :
 
-    as_fn_append LIBMPDEC_CFLAGS " -DTEST_COVERAGE"
 
-fi
+if test $pkg_failed = yes; then
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
 
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
 fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LIBMPDEC_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libmpdec" 2>&1`
+        else
+	        LIBMPDEC_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libmpdec" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LIBMPDEC_PKG_ERRORS" >&5
 
+	LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
+     LIBMPDEC_LIBS=${LIBMPDEC_LIBS-"-lmpdec -lm"}
+     LIBMPDEC_INTERNAL=
+elif test $pkg_failed = untried; then
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+	LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
+     LIBMPDEC_LIBS=${LIBMPDEC_LIBS-"-lmpdec -lm"}
+     LIBMPDEC_INTERNAL=
+else
+	LIBMPDEC_CFLAGS=$pkg_cv_LIBMPDEC_CFLAGS
+	LIBMPDEC_LIBS=$pkg_cv_LIBMPDEC_LIBS
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
 
+fi
+else $as_nop
+  LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
+   LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
+   LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
+fi
 
+# Disable forced inlining in debug builds, see GH-94847
+if test "x$with_pydebug" = xyes
+then :
+  as_fn_append LIBMPDEC_CFLAGS " -DTEST_COVERAGE"
+fi
 
 # Check whether _decimal should use a coroutine-local or thread-local context
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for --with-decimal-contextvar" >&5
@@ -14461,51 +14532,53 @@ fi
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $with_decimal_contextvar" >&5
 printf "%s\n" "$with_decimal_contextvar" >&6; }
 
-# Check for libmpdec machine flavor
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for decimal libmpdec machine" >&5
+if test "x$with_system_libmpdec" = xno
+then :
+  # Check for libmpdec machine flavor
+   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for decimal libmpdec machine" >&5
 printf %s "checking for decimal libmpdec machine... " >&6; }
-case $ac_sys_system in #(
+   case $ac_sys_system in #(
   Darwin*) :
     libmpdec_system=Darwin ;; #(
   SunOS*) :
     libmpdec_system=sunos ;; #(
   *) :
     libmpdec_system=other
- ;;
+    ;;
 esac
 
-libmpdec_machine=unknown
-if test "$libmpdec_system" = Darwin; then
-    # universal here means: build libmpdec with the same arch options
-    # the python interpreter was built with
-    libmpdec_machine=universal
-elif test $ac_cv_sizeof_size_t -eq 8; then
-    if test "$ac_cv_gcc_asm_for_x64" = yes; then
-        libmpdec_machine=x64
-    elif test "$ac_cv_type___uint128_t" = yes; then
-        libmpdec_machine=uint128
-    else
-        libmpdec_machine=ansi64
-    fi
-elif test $ac_cv_sizeof_size_t -eq 4; then
-    if test "$ac_cv_gcc_asm_for_x87" = yes -a "$libmpdec_system" != sunos; then
-        case $CC in #(
+   libmpdec_machine=unknown
+   if test "$libmpdec_system" = Darwin; then
+       # universal here means: build libmpdec with the same arch options
+       # the python interpreter was built with
+       libmpdec_machine=universal
+   elif test $ac_cv_sizeof_size_t -eq 8; then
+       if test "$ac_cv_gcc_asm_for_x64" = yes; then
+           libmpdec_machine=x64
+       elif test "$ac_cv_type___uint128_t" = yes; then
+           libmpdec_machine=uint128
+       else
+           libmpdec_machine=ansi64
+       fi
+   elif test $ac_cv_sizeof_size_t -eq 4; then
+       if test "$ac_cv_gcc_asm_for_x87" = yes -a "$libmpdec_system" != sunos; then
+           case $CC in #(
   *gcc*) :
     libmpdec_machine=ppro ;; #(
   *clang*) :
     libmpdec_machine=ppro ;; #(
   *) :
     libmpdec_machine=ansi32
-         ;;
+            ;;
 esac
-    else
-        libmpdec_machine=ansi32
-    fi
-fi
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libmpdec_machine" >&5
+       else
+           libmpdec_machine=ansi32
+       fi
+   fi
+   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libmpdec_machine" >&5
 printf "%s\n" "$libmpdec_machine" >&6; }
 
-case $libmpdec_machine in #(
+   case $libmpdec_machine in #(
   x64) :
     as_fn_append LIBMPDEC_CFLAGS " -DCONFIG_64=1 -DASM=1" ;; #(
   uint128) :
@@ -14522,8 +14595,9 @@ case $libmpdec_machine in #(
     as_fn_append LIBMPDEC_CFLAGS " -DUNIVERSAL=1" ;; #(
   *) :
     as_fn_error $? "_decimal: unsupported architecture" "$LINENO" 5
- ;;
+    ;;
 esac
+fi
 
 if test "$have_ipa_pure_const_bug" = yes; then
     # Some versions of gcc miscompile inline asm:
@@ -14542,6 +14616,9 @@ fi
 
 
 
+
+
+
   if test "$ac_sys_system" = "Emscripten" -a -z "$LIBSQLITE3_CFLAGS" -a -z "$LIBSQLITE3_LIBS"
 then :
 
@@ -29816,7 +29893,7 @@ fi
 then :
 
     as_fn_append MODULE_BLOCK "MODULE__DECIMAL_CFLAGS=$LIBMPDEC_CFLAGS$as_nl"
-    as_fn_append MODULE_BLOCK "MODULE__DECIMAL_LDFLAGS=$LIBMPDEC_LDFLAGS$as_nl"
+    as_fn_append MODULE_BLOCK "MODULE__DECIMAL_LDFLAGS=$LIBMPDEC_LIBS$as_nl"
 
 fi
    if test "$py_cv_module__decimal" = yes; then
diff --git a/configure.ac b/configure.ac
index b39af7422c4c7c..2a4d1df3403078 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3799,23 +3799,21 @@ AC_ARG_WITH(
   [with_system_libmpdec="no"])
 AC_MSG_RESULT([$with_system_libmpdec])
 
-AS_VAR_IF([with_system_libmpdec], [yes], [
-  LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
-  LIBMPDEC_LDFLAGS=${LIBMPDEC_LDFLAGS-"-lmpdec"}
-  LIBMPDEC_INTERNAL=
-], [
-  LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
-  LIBMPDEC_LDFLAGS="-lm \$(LIBMPDEC_A)"
-  LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"
-
-  dnl Disable forced inlining in debug builds, see GH-94847
-  AS_VAR_IF([with_pydebug], [yes], [
-    AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DTEST_COVERAGE"])
-  ])
-])
-
-AC_SUBST([LIBMPDEC_CFLAGS])
-AC_SUBST([LIBMPDEC_INTERNAL])
+AS_VAR_IF(
+  [with_system_libmpdec], [yes],
+  [PKG_CHECK_MODULES(
+    [LIBMPDEC], [libmpdec], [],
+    [LIBMPDEC_CFLAGS=${LIBMPDEC_CFLAGS-""}
+     LIBMPDEC_LIBS=${LIBMPDEC_LIBS-"-lmpdec -lm"}
+     LIBMPDEC_INTERNAL=])],
+  [LIBMPDEC_CFLAGS="-I\$(srcdir)/Modules/_decimal/libmpdec"
+   LIBMPDEC_LIBS="-lm \$(LIBMPDEC_A)"
+   LIBMPDEC_INTERNAL="\$(LIBMPDEC_HEADERS) \$(LIBMPDEC_A)"])
+
+# Disable forced inlining in debug builds, see GH-94847
+AS_VAR_IF(
+  [with_pydebug], [yes],
+  [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DTEST_COVERAGE"])])
 
 # Check whether _decimal should use a coroutine-local or thread-local context
 AC_MSG_CHECKING([for --with-decimal-contextvar])
@@ -3836,50 +3834,52 @@ fi
 
 AC_MSG_RESULT([$with_decimal_contextvar])
 
-# Check for libmpdec machine flavor
-AC_MSG_CHECKING([for decimal libmpdec machine])
-AS_CASE([$ac_sys_system],
-  [Darwin*], [libmpdec_system=Darwin],
-  [SunOS*], [libmpdec_system=sunos],
-  [libmpdec_system=other]
-)
-
-libmpdec_machine=unknown
-if test "$libmpdec_system" = Darwin; then
-    # universal here means: build libmpdec with the same arch options
-    # the python interpreter was built with
-    libmpdec_machine=universal
-elif test $ac_cv_sizeof_size_t -eq 8; then
-    if test "$ac_cv_gcc_asm_for_x64" = yes; then
-        libmpdec_machine=x64
-    elif test "$ac_cv_type___uint128_t" = yes; then
-        libmpdec_machine=uint128
-    else
-        libmpdec_machine=ansi64
-    fi
-elif test $ac_cv_sizeof_size_t -eq 4; then
-    if test "$ac_cv_gcc_asm_for_x87" = yes -a "$libmpdec_system" != sunos; then
-        AS_CASE([$CC],
-            [*gcc*],   [libmpdec_machine=ppro],
-            [*clang*], [libmpdec_machine=ppro],
-            [libmpdec_machine=ansi32]
-        )
-    else
-        libmpdec_machine=ansi32
-    fi
-fi
-AC_MSG_RESULT([$libmpdec_machine])
-
-AS_CASE([$libmpdec_machine],
-  [x64],         [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DASM=1"])],
-  [uint128],     [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DANSI=1 -DHAVE_UINT128_T=1"])],
-  [ansi64],      [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DANSI=1"])],
-  [ppro],        [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1 -DASM=1 -Wno-unknown-pragmas"])],
-  [ansi32],      [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1"])],
-  [ansi-legacy], [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1 -DLEGACY_COMPILER=1"])],
-  [universal],   [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DUNIVERSAL=1"])],
-  [AC_MSG_ERROR([_decimal: unsupported architecture])]
-)
+AS_VAR_IF(
+  [with_system_libmpdec], [no],
+  [# Check for libmpdec machine flavor
+   AC_MSG_CHECKING([for decimal libmpdec machine])
+   AS_CASE([$ac_sys_system],
+     [Darwin*], [libmpdec_system=Darwin],
+     [SunOS*], [libmpdec_system=sunos],
+     [libmpdec_system=other]
+   )
+
+   libmpdec_machine=unknown
+   if test "$libmpdec_system" = Darwin; then
+       # universal here means: build libmpdec with the same arch options
+       # the python interpreter was built with
+       libmpdec_machine=universal
+   elif test $ac_cv_sizeof_size_t -eq 8; then
+       if test "$ac_cv_gcc_asm_for_x64" = yes; then
+           libmpdec_machine=x64
+       elif test "$ac_cv_type___uint128_t" = yes; then
+           libmpdec_machine=uint128
+       else
+           libmpdec_machine=ansi64
+       fi
+   elif test $ac_cv_sizeof_size_t -eq 4; then
+       if test "$ac_cv_gcc_asm_for_x87" = yes -a "$libmpdec_system" != sunos; then
+           AS_CASE([$CC],
+               [*gcc*],   [libmpdec_machine=ppro],
+               [*clang*], [libmpdec_machine=ppro],
+               [libmpdec_machine=ansi32]
+           )
+       else
+           libmpdec_machine=ansi32
+       fi
+   fi
+   AC_MSG_RESULT([$libmpdec_machine])
+
+   AS_CASE([$libmpdec_machine],
+     [x64],         [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DASM=1"])],
+     [uint128],     [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DANSI=1 -DHAVE_UINT128_T=1"])],
+     [ansi64],      [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_64=1 -DANSI=1"])],
+     [ppro],        [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1 -DASM=1 -Wno-unknown-pragmas"])],
+     [ansi32],      [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1"])],
+     [ansi-legacy], [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DCONFIG_32=1 -DANSI=1 -DLEGACY_COMPILER=1"])],
+     [universal],   [AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -DUNIVERSAL=1"])],
+     [AC_MSG_ERROR([_decimal: unsupported architecture])]
+   )])
 
 if test "$have_ipa_pure_const_bug" = yes; then
     # Some versions of gcc miscompile inline asm:
@@ -3894,6 +3894,9 @@ if test "$have_glibc_memmove_bug" = yes; then
     AS_VAR_APPEND([LIBMPDEC_CFLAGS], [" -U_FORTIFY_SOURCE"])
 fi
 
+AC_SUBST([LIBMPDEC_CFLAGS])
+AC_SUBST([LIBMPDEC_INTERNAL])
+
 
 dnl detect sqlite3 from Emscripten emport
 PY_CHECK_EMSCRIPTEN_PORT([LIBSQLITE3], [-sUSE_SQLITE3])
@@ -7409,7 +7412,7 @@ PY_STDLIB_MOD([_curses_panel],
   [], [test "$have_panel" != "no"],
   [$PANEL_CFLAGS $CURSES_CFLAGS], [$PANEL_LIBS $CURSES_LIBS]
 )
-PY_STDLIB_MOD([_decimal], [], [], [$LIBMPDEC_CFLAGS], [$LIBMPDEC_LDFLAGS])
+PY_STDLIB_MOD([_decimal], [], [], [$LIBMPDEC_CFLAGS], [$LIBMPDEC_LIBS])
 PY_STDLIB_MOD([_dbm],
   [test -n "$with_dbmliborder"], [test "$have_dbm" != "no"],
   [$DBM_CFLAGS], [$DBM_LIBS])

From e899ade99378d7ee0f72ce7b34d0a162f1f50bae Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Tue, 13 Feb 2024 15:39:23 +0100
Subject: [PATCH 2/4] Docs

---
 Doc/using/configure.rst                             | 13 +++++++++++++
 .../2024-02-13-15-31-28.gh-issue-115119.FnQzAW.rst  |  2 ++
 2 files changed, 15 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Build/2024-02-13-15-31-28.gh-issue-115119.FnQzAW.rst

diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
index aab9469b44828a..d4d598754ce8f6 100644
--- a/Doc/using/configure.rst
+++ b/Doc/using/configure.rst
@@ -387,6 +387,17 @@ Options for third-party dependencies
    C compiler and linker flags for ``libffi``, used by :mod:`ctypes` module,
    overriding ``pkg-config``.
 
+.. envvar:: LIBMPDEC_CFLAGS
+.. envvar:: LIBMPDEC_LIBS
+
+   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
 
@@ -787,6 +798,8 @@ Libraries options
 
    .. versionadded:: 3.3
 
+   .. seealso:: :envvar:`LIBMPDEC_CFLAGS` and :envvar:`LIBMPDEC_LIBS`.
+
 .. option:: --with-readline=readline|editline
 
    Designate a backend library for the :mod:`readline` module.
diff --git a/Misc/NEWS.d/next/Build/2024-02-13-15-31-28.gh-issue-115119.FnQzAW.rst b/Misc/NEWS.d/next/Build/2024-02-13-15-31-28.gh-issue-115119.FnQzAW.rst
new file mode 100644
index 00000000000000..5111d8f4db6b83
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2024-02-13-15-31-28.gh-issue-115119.FnQzAW.rst
@@ -0,0 +1,2 @@
+:program:`configure` now uses :program:`pkg-config` to detect :mod:`decimal`
+dependencies if the :option:`--with-system-libmpdec` option is given.

From 1d26811fe4be84ef7499bec34984636408b090d4 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Tue, 13 Feb 2024 15:47:25 +0100
Subject: [PATCH 3/4] Mark up configure env vars as options for consistency
 with the rest of the file

---
 Doc/using/configure.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
index d4d598754ce8f6..c8a1f6441250ac 100644
--- a/Doc/using/configure.rst
+++ b/Doc/using/configure.rst
@@ -387,8 +387,8 @@ Options for third-party dependencies
    C compiler and linker flags for ``libffi``, used by :mod:`ctypes` module,
    overriding ``pkg-config``.
 
-.. envvar:: LIBMPDEC_CFLAGS
-.. envvar:: LIBMPDEC_LIBS
+.. option:: LIBMPDEC_CFLAGS
+.. option:: LIBMPDEC_LIBS
 
    C compiler and linker flags for ``libmpdec``, used by :mod:`decimal` module,
    overriding ``pkg-config``.
@@ -798,7 +798,7 @@ Libraries options
 
    .. versionadded:: 3.3
 
-   .. seealso:: :envvar:`LIBMPDEC_CFLAGS` and :envvar:`LIBMPDEC_LIBS`.
+   .. seealso:: :option:`LIBMPDEC_CFLAGS` and :option:`LIBMPDEC_LIBS`.
 
 .. option:: --with-readline=readline|editline
 

From 4ccb592dcc4bddfdcc2aa1c4f3d6da74a297af97 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Wed, 10 Apr 2024 00:01:56 +0200
Subject: [PATCH 4/4] ifdefs

---
 Modules/_decimal/_decimal.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
index 0df6d5fe1c932e..82b2b4abf83407 100644
--- a/Modules/_decimal/_decimal.c
+++ b/Modules/_decimal/_decimal.c
@@ -38,9 +38,13 @@
 
 // Reuse config from mpdecimal.h if present.
 #if defined(MPD_CONFIG_64)
-  #define CONFIG_64 MPD_CONFIG_64
+  #ifndef CONFIG_64
+    #define CONFIG_64 MPD_CONFIG_64
+  #endif
 #elif defined(MPD_CONFIG_32)
-  #define CONFIG_32 MPD_CONFIG_32
+  #ifndef CONFIG_32
+    #define CONFIG_32 MPD_CONFIG_32
+  #endif
 #endif
 
 #include <ctype.h>                // isascii()