From 934a7abcb6d69e237d63d7fca61c661ca7483de7 Mon Sep 17 00:00:00 2001 From: Chris Lalancette Date: Tue, 13 Feb 2024 21:25:55 +0000 Subject: [PATCH] Set hints to find the python version we actually want. The comment in the commit explains the reasoning behind it. Signed-off-by: Chris Lalancette --- ament_cmake_core/cmake/core/python.cmake | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/ament_cmake_core/cmake/core/python.cmake b/ament_cmake_core/cmake/core/python.cmake index 5820821d..204f002a 100644 --- a/ament_cmake_core/cmake/core/python.cmake +++ b/ament_cmake_core/cmake/core/python.cmake @@ -18,5 +18,21 @@ # find_package(Python3 3.8 REQUIRED) # find_package(ament_cmake REQUIRED) if(NOT TARGET Python3::Interpreter) + # By default, without the settings below, find_package(Python3) will attempt + # to find the newest python version it can, and additionally will find the + # most specific version. For instance, on a system that has + # /usr/bin/python3.10, /usr/bin/python3.11, and /usr/bin/python3, it will find + # /usr/bin/python3.11, even if /usr/bin/python3 points to /usr/bin/python3.10. + # The behavior we want is to prefer the "system" installed version unless the + # user specifically tells us othewise through the Python3_EXECUTABLE hint. + # Setting CMP0094 to NEW means that the search will stop after the first + # python version is found. Setting Python3_FIND_UNVERSIONED_NAMES means that + # the search will prefer /usr/bin/python3 over /usr/bin/python3.11. And that + # latter functionality is only available in CMake 3.20 or later, so we need + # at least that version. + cmake_minimum_required(VERSION 3.20) + cmake_policy(SET CMP0094 NEW) + set(Python3_FIND_UNVERSIONED_NAMES FIRST) + find_package(Python3 REQUIRED COMPONENTS Interpreter) endif()