From b4a110f54e66190736a93f91530beb25480ef86f Mon Sep 17 00:00:00 2001 From: Michael Carroll Date: Sat, 22 Aug 2026 10:44:17 -0700 Subject: [PATCH] Skip redundant find_package(Python3) in generator extensions Every rosidl generator extension calls find_package(Python3 REQUIRED COMPONENTS ...) unconditionally. Because ament_execute_extensions includes each extension into the same scope, a single interface package runs that search once per registered generator -- 13 times for a default rolling workspace. CMake does not memoize this. Each repeat re-enters FindPython/Support.cmake and re-interrogates the interpreter with roughly seven subprocesses. On Windows, where CreateProcess for python.exe costs ~60ms locally and far more on a CI runner, the repeats dominate configure time. Guard each call on the imported target, exactly as ament_cmake_core's python.cmake already does. Imported targets are directory scoped, so the target created by the first search is visible to every later extension. Companion to ros2/rosidl. With all four repos patched, configure of builtin_interfaces drops from 17.6s to 13.1s on Windows (median of 5), python.exe spawns from 92 to 22, and the generated build.ninja is byte identical. Signed-off-by: Michael Carroll --- ...idl_generator_py_generate_interfaces.cmake | 37 ++++++++++--------- 1 file changed, 20 insertions(+), 17 deletions(-) diff --git a/rosidl_generator_py/cmake/rosidl_generator_py_generate_interfaces.cmake b/rosidl_generator_py/cmake/rosidl_generator_py_generate_interfaces.cmake index 2fe245b1..2810984c 100644 --- a/rosidl_generator_py/cmake/rosidl_generator_py_generate_interfaces.cmake +++ b/rosidl_generator_py/cmake/rosidl_generator_py_generate_interfaces.cmake @@ -17,23 +17,26 @@ find_package(rosidl_runtime_c REQUIRED) find_package(rosidl_typesupport_c REQUIRED) find_package(rosidl_typesupport_interface REQUIRED) -# 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 Development NumPy) +# Development gives Python3::Module, NumPy gives Python3::NumPy. +if(NOT TARGET Python3::Module OR NOT TARGET Python3::NumPy) + # 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 Development NumPy) +endif() # Get a list of typesupport implementations from valid rmw implementations. rosidl_generator_py_get_typesupports(_typesupport_impls)