gh-100540: Remove obsolete '--with-system-ffi' configure option (GH-100544)

It has had no effect on non-macOS platforms for a long time, and has had
the non-obvious effect of invoking `pkg_config` and not setting
`-DUSING_APPLE_OS_LIBFFI` on macOS since GH-22855.

4 files changed, 87 insertions, 156 deletions

diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
index db4bf74..8fa8d25 100644
--- a/Doc/using/configure.rst
+++ b/Doc/using/configure.rst
@@ -471,11 +471,6 @@ Libraries options
    Build the :mod:`pyexpat` module using an installed ``expat`` library
    (default is no).
 
-.. cmdoption:: --with-system-ffi
-
-   Build the :mod:`_ctypes` extension module using an installed ``ffi``
-   library, see the :mod:`ctypes` module (default is system-dependent).
-
 .. cmdoption:: --with-system-libmpdec
 
    Build the ``_decimal`` extension module using an installed ``mpdec``
diff --git a/Misc/NEWS.d/next/Build/2022-12-26-15-07-48.gh-issue-100540.l6ToSY.rst b/Misc/NEWS.d/next/Build/2022-12-26-15-07-48.gh-issue-100540.l6ToSY.rst
new file mode 100644
index 0000000..c924ab5
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2022-12-26-15-07-48.gh-issue-100540.l6ToSY.rst
@@ -0,0 +1,8 @@
+Removed the ``--with-system-ffi`` ``configure`` option; ``libffi`` must
+now always be supplied by the system on all non-Windows platforms.  The
+option has had no effect on non-Darwin platforms for several releases, and
+in 3.11 only had the non-obvious effect of invoking ``pkg-config`` to
+find ``libffi`` and never setting ``-DUSING_APPLE_OS_LIBFFI``.  Now on
+Darwin platforms ``configure`` will first check for the OS ``libffi`` and
+then fall back to the same processing as other platforms if it is not
+found.
diff --git a/configure b/configure
index 7229993..6afd1e9 100755
--- a/configure
+++ b/configure
@@ -1064,7 +1064,6 @@ with_hash_algorithm
 with_tzpath
 with_libs
 with_system_expat
-with_system_ffi
 with_system_libmpdec
 with_decimal_contextvar
 enable_loadable_sqlite_extensions
@@ -1847,9 +1846,6 @@ Optional Packages:
   --with-libs='lib1 ...'  link against additional libs (default is no)
   --with-system-expat     build pyexpat module using an installed expat
                           library, see Doc/library/pyexpat.rst (default is no)
-  --with-system-ffi       build _ctypes module using an installed ffi library,
-                          see Doc/library/ctypes.rst (default is
-                          system-dependent)
   --with-system-libmpdec  build _decimal module using an installed libmpdec
                           library, see Doc/library/decimal.rst (default is no)
   --with-decimal-contextvar
@@ -12516,43 +12512,77 @@ fi
 
 
 
-# Check for use of the system libffi library
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-system-ffi" >&5
-$as_echo_n "checking for --with-system-ffi... " >&6; }
+have_libffi=missing
+if test "x$ac_sys_system" = xDarwin; then :
 
-# Check whether --with-system_ffi was given.
-if test "${with_system_ffi+set}" = set; then :
-  withval=$with_system_ffi;
-fi
+  save_CFLAGS=$CFLAGS
+save_CPPFLAGS=$CPPFLAGS
+save_LDFLAGS=$LDFLAGS
+save_LIBS=$LIBS
 
 
-if test "$ac_sys_system" = "Darwin"
-then
-    case "$with_system_ffi" in
-        "")
-            with_system_ffi="no"
-            ;;
-        yes|no)
-            ;;
-        *)
-            as_fn_error $? "--with-system-ffi accepts no arguments" "$LINENO" 5
-            ;;
-    esac
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_system_ffi" >&5
-$as_echo "$with_system_ffi" >&6; }
+    CFLAGS="-I${SDKROOT}/usr/include/ffi $CFLAGS"
+    ac_fn_c_check_header_mongrel "$LINENO" "ffi.h" "ac_cv_header_ffi_h" "$ac_includes_default"
+if test "x$ac_cv_header_ffi_h" = xyes; then :
+
+      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ffi_call in -lffi" >&5
+$as_echo_n "checking for ffi_call in -lffi... " >&6; }
+if ${ac_cv_lib_ffi_ffi_call+:} false; then :
+  $as_echo_n "(cached) " >&6
 else
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-    if test "$with_system_ffi" != ""
-    then
-        { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: --with(out)-system-ffi is ignored on this platform" >&5
-$as_echo "$as_me: WARNING: --with(out)-system-ffi is ignored on this platform" >&2;}
-    fi
-    with_system_ffi="yes"
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lffi  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ffi_call ();
+int
+main ()
+{
+return ffi_call ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_ffi_ffi_call=yes
+else
+  ac_cv_lib_ffi_ffi_call=no
 fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_ffi_ffi_call" >&5
+$as_echo "$ac_cv_lib_ffi_ffi_call" >&6; }
+if test "x$ac_cv_lib_ffi_ffi_call" = xyes; then :
 
-have_libffi=missing
-if test "x$with_system_ffi" = xyes; then :
+                have_libffi=yes
+        LIBFFI_CFLAGS="-I${SDKROOT}/usr/include/ffi -DUSING_APPLE_OS_LIBFFI=1"
+        LIBFFI_LIBS="-lffi"
+
+fi
+
+
+fi
+
+
+
+CFLAGS=$save_CFLAGS
+CPPFLAGS=$save_CPPFLAGS
+LDFLAGS=$save_LDFLAGS
+LIBS=$save_LIBS
+
+
+
+fi
+if test "x$have_libffi" = xmissing; then :
 
 
 pkg_failed=no
@@ -12764,80 +12794,6 @@ $as_echo "yes" >&6; }
 	have_libffi=yes
 fi
 
-else
-
-  if test "x$ac_sys_system" = xDarwin; then :
-
-    save_CFLAGS=$CFLAGS
-save_CPPFLAGS=$CPPFLAGS
-save_LDFLAGS=$LDFLAGS
-save_LIBS=$LIBS
-
-
-      CFLAGS="-I${SDKROOT}/usr/include/ffi $CFLAGS"
-      ac_fn_c_check_header_mongrel "$LINENO" "ffi.h" "ac_cv_header_ffi_h" "$ac_includes_default"
-if test "x$ac_cv_header_ffi_h" = xyes; then :
-
-        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ffi_call in -lffi" >&5
-$as_echo_n "checking for ffi_call in -lffi... " >&6; }
-if ${ac_cv_lib_ffi_ffi_call+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_check_lib_save_LIBS=$LIBS
-LIBS="-lffi  $LIBS"
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-/* Override any GCC internal prototype to avoid an error.
-   Use char because int might match the return type of a GCC
-   builtin and then its argument prototype would still apply.  */
-#ifdef __cplusplus
-extern "C"
-#endif
-char ffi_call ();
-int
-main ()
-{
-return ffi_call ();
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_lib_ffi_ffi_call=yes
-else
-  ac_cv_lib_ffi_ffi_call=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-LIBS=$ac_check_lib_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_ffi_ffi_call" >&5
-$as_echo "$ac_cv_lib_ffi_ffi_call" >&6; }
-if test "x$ac_cv_lib_ffi_ffi_call" = xyes; then :
-
-                    have_libffi=yes
-          LIBFFI_CFLAGS="-I${SDKROOT}/usr/include/ffi -DUSING_APPLE_OS_LIBFFI=1"
-          LIBFFI_LIBS="-lffi"
-
-else
-  have_libffi=no
-fi
-
-
-fi
-
-
-
-CFLAGS=$save_CFLAGS
-CPPFLAGS=$save_CPPFLAGS
-LDFLAGS=$save_LDFLAGS
-LIBS=$save_LIBS
-
-
-
-fi
-
 fi
 
 if test "x$have_libffi" = xyes; then :
diff --git a/configure.ac b/configure.ac
index d6499be..4873664 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3705,36 +3705,22 @@ AS_VAR_IF([with_system_expat], [yes], [
 AC_SUBST([LIBEXPAT_CFLAGS])
 AC_SUBST([LIBEXPAT_INTERNAL])
 
-# Check for use of the system libffi library
-AC_MSG_CHECKING(for --with-system-ffi)
-AC_ARG_WITH(system_ffi,
-            AS_HELP_STRING([--with-system-ffi], [build _ctypes module using an installed ffi library, see Doc/library/ctypes.rst (default is system-dependent)]),,,)
-
-if test "$ac_sys_system" = "Darwin"
-then
-    case "$with_system_ffi" in
-        "")
-            with_system_ffi="no"
-            ;;
-        yes|no)
-            ;;
-        *)
-            AC_MSG_ERROR([--with-system-ffi accepts no arguments])
-            ;;
-    esac
-    AC_MSG_RESULT($with_system_ffi)
-else
-    AC_MSG_RESULT(yes)
-    if test "$with_system_ffi" != ""
-    then
-        AC_MSG_WARN([--with(out)-system-ffi is ignored on this platform])
-    fi
-    with_system_ffi="yes"
-fi
-
 dnl detect libffi
 have_libffi=missing
-AS_VAR_IF([with_system_ffi], [yes], [
+AS_VAR_IF([ac_sys_system], [Darwin], [
+  WITH_SAVE_ENV([
+    CFLAGS="-I${SDKROOT}/usr/include/ffi $CFLAGS"
+    AC_CHECK_HEADER([ffi.h], [
+      AC_CHECK_LIB([ffi], [ffi_call], [
+        dnl use ffi from SDK root
+        have_libffi=yes
+        LIBFFI_CFLAGS="-I${SDKROOT}/usr/include/ffi -DUSING_APPLE_OS_LIBFFI=1"
+        LIBFFI_LIBS="-lffi"
+      ])
+    ])
+  ])
+])
+AS_VAR_IF([have_libffi], [missing], [
   PKG_CHECK_MODULES([LIBFFI], [libffi], [have_libffi=yes], [
     WITH_SAVE_ENV([
       CPPFLAGS="$CPPFLAGS $LIBFFI_CFLAGS"
@@ -3748,20 +3734,6 @@ AS_VAR_IF([with_system_ffi], [yes], [
       ])
     ])
   ])
-], [
-  AS_VAR_IF([ac_sys_system], [Darwin], [
-    WITH_SAVE_ENV([
-      CFLAGS="-I${SDKROOT}/usr/include/ffi $CFLAGS"
-      AC_CHECK_HEADER([ffi.h], [
-        AC_CHECK_LIB([ffi], [ffi_call], [
-          dnl use ffi from SDK root
-          have_libffi=yes
-          LIBFFI_CFLAGS="-I${SDKROOT}/usr/include/ffi -DUSING_APPLE_OS_LIBFFI=1"
-          LIBFFI_LIBS="-lffi"
-        ], [have_libffi=no])
-      ])
-    ])
-  ])
 ])
 
 AS_VAR_IF([have_libffi], [yes], [