python: Update python.m4 configure script.

* configure.ac: Unset PYTHON_LIBS.  Support python 3.10.
* m4/python.m4: Find correct version string for python >= 3.10.
--

See-also: https://dev.gnupg.org/D546

Also test for 3.11 and 3.12 (wk).

2 files changed, 198 insertions, 91 deletions

diff --git a/configure.ac b/configure.ac
index dfcaac31..83ac09de 100644
--- a/configure.ac
+++ b/configure.ac
@@ -521,11 +521,13 @@ if test "$found_py" = "1"; then
 	if test "$found_py" = "1" -o "$found_py3" = "1"; then
 	  # Reset everything, so that we can look for another Python.
           m4_foreach([mym4pythonver],
-                     [[2.7],[3.4],[3.5],[3.6],[3.7],[3.8],[3.9],[all]],
+                     [[2.7],[3.4],[3.5],[3.6],[3.7],[3.8],[3.9],[3.10],
+                      [3.11],[3.12],[all]],
            [unset PYTHON
 	    unset PYTHON_VERSION
 	    unset PYTHON_CPPFLAGS
 	    unset PYTHON_LDFLAGS
+	    unset PYTHON_LIBS
 	    unset PYTHON_SITE_PKG
 	    unset PYTHON_EXTRA_LIBS
 	    unset PYTHON_EXTRA_LDFLAGS
diff --git a/m4/python.m4 b/m4/python.m4
index fd0fe771..4b9483c0 100644
--- a/m4/python.m4
+++ b/m4/python.m4
@@ -1,10 +1,10 @@
 ## ------------------------                                 -*- Autoconf -*-
 ## Python file handling
 ## From Andrew Dalke
-## Updated by James Henstridge
+## Updated by James Henstridge and other contributors.
 ## Updated by Werner Koch 2018-10-17
-## ---------------------------------
-# Copyright (C) 1999-2017 Free Software Foundation, Inc.
+## ------------------------
+# Copyright (C) 1999-2021 Free Software Foundation, Inc.
 #
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -36,13 +36,12 @@
 # numbers and dots only.
 AC_DEFUN([AM_PATH_PYTHON],
  [
-  dnl Find a Python interpreter.  Python versions prior to 2.0 are not
-  dnl supported. (2.0 was released on October 16, 2000).  Python 3.0
-  dnl through to Python 3.9 are also not supported.
+  dnl Find a Python interpreter.  Python versions prior to 2.7 are not
+  dnl supported. Python 3.0 through to Python 3.3 are also not supported.
   m4_define_default([_AM_PYTHON_INTERPRETER_LIST],
 [python2 python2.7 dnl
  python dnl
- python3 python3.9 python3.8 python3.7 python3.6 python3.5 python3.4
+ python3 python3.10 python3.9 python3.8 python3.7 python3.6 python3.5 python3.4
  ])
 
   AC_ARG_VAR([PYTHON], [the Python interpreter])
@@ -85,34 +84,141 @@ AC_DEFUN([AM_PATH_PYTHON],
   ])
 
   if test "$PYTHON" = :; then
-  dnl Run any user-specified action, or abort.
+    dnl Run any user-specified action, or abort.
     m4_default([$3], [AC_MSG_ERROR([no suitable Python interpreter found])])
   else
 
-  dnl Query Python for its version number.  Getting [:3] seems to be
-  dnl the best way to do this; it's what "site.py" does in the standard
-  dnl library.
-
+  dnl Query Python for its version number.  Although site.py simply uses
+  dnl sys.version[:3], printing that failed with Python 3.10, since the
+  dnl trailing zero was eliminated. So now we output just the major
+  dnl and minor version numbers, as numbers. Apparently the tertiary
+  dnl version is not of interest.
+  dnl
   AC_CACHE_CHECK([for $am_display_PYTHON version], [am_cv_python_version],
-    [am_cv_python_version=`$PYTHON -c "import sys; sys.stdout.write(sys.version[[:3]])"`])
+    [am_cv_python_version=`$PYTHON -c "import sys; print ('%u.%u' % sys.version_info[[:2]])"`])
   AC_SUBST([PYTHON_VERSION], [$am_cv_python_version])
 
-  dnl Use the values of $prefix and $exec_prefix for the corresponding
-  dnl values of PYTHON_PREFIX and PYTHON_EXEC_PREFIX.  These are made
-  dnl distinct variables so they can be overridden if need be.  However,
-  dnl general consensus is that you shouldn't need this ability.
-
-  AC_SUBST([PYTHON_PREFIX], ['${prefix}'])
-  AC_SUBST([PYTHON_EXEC_PREFIX], ['${exec_prefix}'])
-
-  dnl At times (like when building shared libraries) you may want
+  dnl At times, e.g., when building shared libraries, you may want
   dnl to know which OS platform Python thinks this is.
-
+  dnl
   AC_CACHE_CHECK([for $am_display_PYTHON platform], [am_cv_python_platform],
     [am_cv_python_platform=`$PYTHON -c "import sys; sys.stdout.write(sys.platform)"`])
   AC_SUBST([PYTHON_PLATFORM], [$am_cv_python_platform])
 
-  # Just factor out some code duplication.
+  dnl emacs-page
+  dnl If --with-python-sys-prefix is given, use the values of sys.prefix
+  dnl and sys.exec_prefix for the corresponding values of PYTHON_PREFIX
+  dnl and PYTHON_EXEC_PREFIX. Otherwise, use the GNU ${prefix} and
+  dnl ${exec_prefix} variables.
+  dnl
+  dnl The two are made distinct variables so they can be overridden if
+  dnl need be, although general consensus is that you shouldn't need
+  dnl this separation.
+  dnl
+  dnl Also allow directly setting the prefixes via configure options,
+  dnl overriding any default.
+  dnl
+  if test "x$prefix" = xNONE; then
+    am__usable_prefix=$ac_default_prefix
+  else
+    am__usable_prefix=$prefix
+  fi
+
+  # Allow user to request using sys.* values from Python,
+  # instead of the GNU $prefix values.
+  AC_ARG_WITH([python-sys-prefix],
+  [AS_HELP_STRING([--with-python-sys-prefix],
+                  [use Python's sys.prefix and sys.exec_prefix values])],
+  [am_use_python_sys=:],
+  [am_use_python_sys=false])
+
+  # Allow user to override whatever the default Python prefix is.
+  AC_ARG_WITH([python_prefix],
+  [AS_HELP_STRING([--with-python_prefix],
+                  [override the default PYTHON_PREFIX])],
+  [am_python_prefix_subst=$withval
+   am_cv_python_prefix=$withval
+   AC_MSG_CHECKING([for explicit $am_display_PYTHON prefix])
+   AC_MSG_RESULT([$am_cv_python_prefix])],
+  [
+   if $am_use_python_sys; then
+     # using python sys.prefix value, not GNU
+     AC_CACHE_CHECK([for python default $am_display_PYTHON prefix],
+     [am_cv_python_prefix],
+     [am_cv_python_prefix=`$PYTHON -c "import sys; sys.stdout.write(sys.prefix)"`])
+
+     dnl If sys.prefix is a subdir of $prefix, replace the literal value of
+     dnl $prefix with a variable reference so it can be overridden.
+     case $am_cv_python_prefix in
+     $am__usable_prefix*)
+       am__strip_prefix=`echo "$am__usable_prefix" | sed 's|.|.|g'`
+       am_python_prefix_subst=`echo "$am_cv_python_prefix" | sed "s,^$am__strip_prefix,\\${prefix},"`
+       ;;
+     *)
+       am_python_prefix_subst=$am_cv_python_prefix
+       ;;
+     esac
+   else # using GNU prefix value, not python sys.prefix
+     am_python_prefix_subst='${prefix}'
+     am_python_prefix=$am_python_prefix_subst
+     AC_MSG_CHECKING([for GNU default $am_display_PYTHON prefix])
+     AC_MSG_RESULT([$am_python_prefix])
+   fi])
+  # Substituting python_prefix_subst value.
+  AC_SUBST([PYTHON_PREFIX], [$am_python_prefix_subst])
+
+  # emacs-page Now do it all over again for Python exec_prefix, but with yet
+  # another conditional: fall back to regular prefix if that was specified.
+  AC_ARG_WITH([python_exec_prefix],
+  [AS_HELP_STRING([--with-python_exec_prefix],
+                  [override the default PYTHON_EXEC_PREFIX])],
+  [am_python_exec_prefix_subst=$withval
+   am_cv_python_exec_prefix=$withval
+   AC_MSG_CHECKING([for explicit $am_display_PYTHON exec_prefix])
+   AC_MSG_RESULT([$am_cv_python_exec_prefix])],
+  [
+   # no explicit --with-python_exec_prefix, but if
+   # --with-python_prefix was given, use its value for python_exec_prefix too.
+   AS_IF([test -n "$with_python_prefix"],
+   [am_python_exec_prefix_subst=$with_python_prefix
+    am_cv_python_exec_prefix=$with_python_prefix
+    AC_MSG_CHECKING([for python_prefix-given $am_display_PYTHON exec_prefix])
+    AC_MSG_RESULT([$am_cv_python_exec_prefix])],
+   [
+    # Set am__usable_exec_prefix whether using GNU or Python values,
+    # since we use that variable for pyexecdir.
+    if test "x$exec_prefix" = xNONE; then
+      am__usable_exec_prefix=$am__usable_prefix
+    else
+      am__usable_exec_prefix=$exec_prefix
+    fi
+    #
+    if $am_use_python_sys; then # using python sys.exec_prefix, not GNU
+      AC_CACHE_CHECK([for python default $am_display_PYTHON exec_prefix],
+      [am_cv_python_exec_prefix],
+      [am_cv_python_exec_prefix=`$PYTHON -c "import sys; sys.stdout.write(sys.exec_prefix)"`])
+      dnl If sys.exec_prefix is a subdir of $exec_prefix, replace the
+      dnl literal value of $exec_prefix with a variable reference so it can
+      dnl be overridden.
+      case $am_cv_python_exec_prefix in
+      $am__usable_exec_prefix*)
+        am__strip_prefix=`echo "$am__usable_exec_prefix" | sed 's|.|.|g'`
+        am_python_exec_prefix_subst=`echo "$am_cv_python_exec_prefix" | sed "s,^$am__strip_prefix,\\${exec_prefix},"`
+        ;;
+      *)
+        am_python_exec_prefix_subst=$am_cv_python_exec_prefix
+        ;;
+     esac
+   else # using GNU $exec_prefix, not python sys.exec_prefix
+     am_python_exec_prefix_subst='${exec_prefix}'
+     am_python_exec_prefix=$am_python_exec_prefix_subst
+     AC_MSG_CHECKING([for GNU default $am_display_PYTHON exec_prefix])
+     AC_MSG_RESULT([$am_python_exec_prefix])
+   fi])])
+  # Substituting python_exec_prefix_subst.
+  AC_SUBST([PYTHON_EXEC_PREFIX], [$am_python_exec_prefix_subst])
+
+  # Factor out some code duplication into this shell variable.
   am_python_setup_sysconfig="\
 import sys
 # Prefer sysconfig over distutils.sysconfig, for better compatibility
@@ -132,96 +238,95 @@ try:
 except ImportError:
     pass"
 
-  dnl Set up 4 directories:
+  dnl emacs-page Set up 4 directories:
 
-  dnl pythondir -- where to install python scripts.  This is the
-  dnl   site-packages directory, not the python standard library
-  dnl   directory like in previous automake betas.  This behavior
-  dnl   is more consistent with lispdir.m4 for example.
+  dnl 1. pythondir: where to install python scripts.  This is the
+  dnl    site-packages directory, not the python standard library
+  dnl    directory like in previous automake betas.  This behavior
+  dnl    is more consistent with lispdir.m4 for example.
   dnl Query distutils for this directory.
-  AC_CACHE_CHECK([for $am_display_PYTHON script directory],
-    [am_cv_python_pythondir],
-    [if test "x$prefix" = xNONE
-     then
-       am_py_prefix=$ac_default_prefix
-     else
-       am_py_prefix=$prefix
-     fi
-     am_cv_python_pythondir=`$PYTHON -c "
+  dnl
+  AC_CACHE_CHECK([for $am_display_PYTHON script directory (pythondir)],
+  [am_cv_python_pythondir],
+  [if test "x$am_cv_python_prefix" = x; then
+     am_py_prefix=$am__usable_prefix
+   else
+     am_py_prefix=$am_cv_python_prefix
+   fi
+   am_cv_python_pythondir=`$PYTHON -c "
 $am_python_setup_sysconfig
 if can_use_sysconfig:
-    sitedir = sysconfig.get_path('purelib', vars={'base':'$am_py_prefix'})
+  sitedir = sysconfig.get_path('purelib', vars={'base':'$am_py_prefix'})
 else:
-    from distutils import sysconfig
-    sitedir = sysconfig.get_python_lib(0, 0, prefix='$am_py_prefix')
+  from distutils import sysconfig
+  sitedir = sysconfig.get_python_lib(0, 0, prefix='$am_py_prefix')
 sys.stdout.write(sitedir)"`
-     case $am_cv_python_pythondir in
-     $am_py_prefix*)
-       am__strip_prefix=`echo "$am_py_prefix" | sed 's|.|.|g'`
-       am_cv_python_pythondir=`echo "$am_cv_python_pythondir" | sed "s,^$am__strip_prefix,$PYTHON_PREFIX,"`
-       ;;
-     *)
-       case $am_py_prefix in
-         /usr|/System*) ;;
-         *)
-	  am_cv_python_pythondir=$PYTHON_PREFIX/lib/python$PYTHON_VERSION/site-packages
-	  ;;
-       esac
-       ;;
+   #
+   case $am_cv_python_pythondir in
+   $am_py_prefix*)
+     am__strip_prefix=`echo "$am_py_prefix" | sed 's|.|.|g'`
+     am_cv_python_pythondir=`echo "$am_cv_python_pythondir" | sed "s,^$am__strip_prefix,\\${PYTHON_PREFIX},"`
+     ;;
+   *)
+     case $am_py_prefix in
+       /usr|/System*) ;;
+       *) am_cv_python_pythondir="\${PYTHON_PREFIX}/lib/python$PYTHON_VERSION/site-packages"
+          ;;
      esac
-    ])
+     ;;
+   esac
+  ])
   AC_SUBST([pythondir], [$am_cv_python_pythondir])
 
-  dnl pkgpythondir -- $PACKAGE directory under pythondir.  Was
-  dnl   PYTHON_SITE_PACKAGE in previous betas, but this naming is
-  dnl   more consistent with the rest of automake.
-
+  dnl 2. pkgpythondir: $PACKAGE directory under pythondir.  Was
+  dnl    PYTHON_SITE_PACKAGE in previous betas, but this naming is
+  dnl    more consistent with the rest of automake.
+  dnl
   AC_SUBST([pkgpythondir], [\${pythondir}/$PACKAGE])
 
-  dnl pyexecdir -- directory for installing python extension modules
-  dnl   (shared libraries)
+  dnl 3. pyexecdir: directory for installing python extension modules
+  dnl    (shared libraries).
   dnl Query distutils for this directory.
-  AC_CACHE_CHECK([for $am_display_PYTHON extension module directory],
-    [am_cv_python_pyexecdir],
-    [if test "x$exec_prefix" = xNONE
-     then
-       am_py_exec_prefix=$am_py_prefix
-     else
-       am_py_exec_prefix=$exec_prefix
-     fi
-     am_cv_python_pyexecdir=`$PYTHON -c "
+  dnl
+  AC_CACHE_CHECK([for $am_display_PYTHON extension module directory (pyexecdir)],
+  [am_cv_python_pyexecdir],
+  [if test "x$am_cv_python_exec_prefix" = x; then
+     am_py_exec_prefix=$am__usable_exec_prefix
+   else
+     am_py_exec_prefix=$am_cv_python_exec_prefix
+   fi
+   am_cv_python_pyexecdir=`$PYTHON -c "
 $am_python_setup_sysconfig
 if can_use_sysconfig:
-    sitedir = sysconfig.get_path('platlib', vars={'platbase':'$am_py_prefix'})
+  sitedir = sysconfig.get_path('platlib', vars={'platbase':'$am_py_exec_prefix'})
 else:
-    from distutils import sysconfig
-    sitedir = sysconfig.get_python_lib(1, 0, prefix='$am_py_prefix')
+  from distutils import sysconfig
+  sitedir = sysconfig.get_python_lib(1, 0, prefix='$am_py_exec_prefix')
 sys.stdout.write(sitedir)"`
-     case $am_cv_python_pyexecdir in
-     $am_py_exec_prefix*)
-       am__strip_prefix=`echo "$am_py_exec_prefix" | sed 's|.|.|g'`
-       am_cv_python_pyexecdir=`echo "$am_cv_python_pyexecdir" | sed "s,^$am__strip_prefix,$PYTHON_EXEC_PREFIX,"`
-       ;;
-     *)
-       case $am_py_exec_prefix in
-         /usr|/System*) ;;
-         *)
-	   am_cv_python_pyexecdir=$PYTHON_EXEC_PREFIX/lib/python$PYTHON_VERSION/site-packages
-	   ;;
-       esac
-       ;;
+   #
+   case $am_cv_python_pyexecdir in
+   $am_py_exec_prefix*)
+     am__strip_prefix=`echo "$am_py_exec_prefix" | sed 's|.|.|g'`
+     am_cv_python_pyexecdir=`echo "$am_cv_python_pyexecdir" | sed "s,^$am__strip_prefix,\\${PYTHON_EXEC_PREFIX},"`
+     ;;
+   *)
+     case $am_py_exec_prefix in
+       /usr|/System*) ;;
+       *) am_cv_python_pyexecdir="\${PYTHON_EXEC_PREFIX}/lib/python$PYTHON_VERSION/site-packages"
+          ;;
      esac
-    ])
+     ;;
+   esac
+  ])
   AC_SUBST([pyexecdir], [$am_cv_python_pyexecdir])
 
-  dnl pkgpyexecdir -- $(pyexecdir)/$(PACKAGE)
-
+  dnl 4. pkgpyexecdir: $(pyexecdir)/$(PACKAGE)
+  dnl
   AC_SUBST([pkgpyexecdir], [\${pyexecdir}/$PACKAGE])
 
   dnl Run any user-specified action.
   $2
   fi
-
 ])