From e21d46fddd0753e66a4acda88317670fee07f3e6 Mon Sep 17 00:00:00 2001
From: "Miro Hron\\v{c}ok" <miro@hroncok.cz>
Date: Tue, 27 Oct 2020 14:33:46 -0700
Subject: [PATCH] python: determine Python (3.10) version number correctly.

This change fixes https://bugs.gnu.org/44239
(and https://bugzilla.redhat.com/show_bug.cgi?id=1889732).

* m4/python.m4: use print('%u.%u' % sys.version_info[:2]) for
the version number instead of merely sys.version[:3], so the
numbers are treated as numbers.
* t/python-vars.sh (PYTHON_VERSION): Likewise.
* doc/automake.texi: Document it.
* NEWS: mention it. (Minor tweaks from Karl Berry.)
---
 NEWS              |  2 ++
 doc/automake.texi |  2 +-
 m4/python.m4      | 12 +++++++-----
 t/python-vars.sh  |  4 +++-
 4 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/NEWS b/NEWS
index fa35bf1..9c69e48 100644
--- a/NEWS
+++ b/NEWS
@@ -74,6 +74,8 @@ New in 1.16.2:
 
 * Bugs fixed
 
+  - Python 3.10 version number no longer considered to be 3.1.
+
   - When cleaning the compiled python files, '\n' is not used anymore in the
     substitution text of 'sed' transformations.  This is done to preserve
     compatibility with the 'sed' implementation provided by macOS which
diff --git a/doc/automake.texi b/doc/automake.texi
index ed7e2e2..17bc2da 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -7861,7 +7861,7 @@ AM_CONDITIONAL([HAVE_PYTHON], [test "$PYTHON" != :])
 @item PYTHON_VERSION
 The Python version number, in the form @var{major}.@var{minor}
 (e.g., @samp{2.5}).  This is currently the value of
-@samp{sys.version[:3]}.
+@samp{'%u.%u' % sys.version_info[:2]}.
 
 @item PYTHON_PREFIX
 The string @samp{$@{prefix@}}.  This term may be used in future work
diff --git a/m4/python.m4 b/m4/python.m4
index 16c2f4f..b2302ba 100644
--- a/m4/python.m4
+++ b/m4/python.m4
@@ -1,7 +1,7 @@
 ## ------------------------                                 -*- Autoconf -*-
 ## Python file handling
 ## From Andrew Dalke
-## Updated by James Henstridge
+## Updated by James Henstridge and other contributors.
 ## ------------------------
 # Copyright (C) 1999-2020 Free Software Foundation, Inc.
 #
@@ -86,12 +86,14 @@ AC_DEFUN([AM_PATH_PYTHON],
     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.
 
   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 $exec_prefix for the corresponding
diff --git a/t/python-vars.sh b/t/python-vars.sh
index 5c748bc..b53018b 100644
--- a/t/python-vars.sh
+++ b/t/python-vars.sh
@@ -28,7 +28,9 @@ CONFIG_SITE=/dev/null; export CONFIG_SITE
 # vary among different python installations, so we need more relaxed
 # and ad-hoc checks for them.  Also, more proper "functional" checks
 # on them should be done in the 'python-virtualenv.sh' test.
-PYTHON_VERSION=$($PYTHON -c 'import sys; print(sys.version[:3])') || exit 1
+# 
+# This version identification is duplicated in python.m4 (and the manual).
+PYTHON_VERSION=$($PYTHON -c 'import sys; print("%u.%u" % sys.version_info[:2])') || exit 1
 PYTHON_PLATFORM=$($PYTHON -c 'import sys; print(sys.platform)') || exit 1
 PYTHON_EXEC_PREFIX='${exec_prefix}'
 PYTHON_PREFIX='${prefix}'
-- 
1.8.3.1

