[BUG]: 'Unknown CMake command "python3_add_library" in pybind11NewTools.cmake

[stridera]

Required prerequisites

• [X] Make sure you've read the documentation. Your issue may be addressed there.
• [X] Search the issue tracker and Discussions to verify that this hasn't already been reported. +1 or comment there if it has.
• [X] Consider asking first in the Gitter chat room or in a Discussion.

Problem description

Attempting to build throws an error in tools/pybind11NewTools.cmake throws the following error: Unknown CMake command "python3_add_library".

Adding find_package (Python3 COMPONENTS Interpreter Development) fixes it.

Reproducible example code

src/cmakelists.txt

configure_file(${CMAKE_SOURCE_DIR}/third_party/pybind11/CMakeLists.txt ${CMAKE_BINARY_DIR}/external-projects/pybind11/CMakeLists.txt)
execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
    WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/external-projects/pybind11"
)
execute_process(COMMAND "${CMAKE_COMMAND}" --build .
    WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/external-projects/pybind11"
)

# Add pybind11 makefile
add_subdirectory("${CMAKE_BINARY_DIR}/third_party/pybind11"
                 "${CMAKE_BINARY_DIR}/third_party/pybind11"
                 EXCLUDE_FROM_ALL
)

set(PYBIND11_CPP_STANDARD -std=c++11)
# Force Pybind11 not to share resources with other pybind modules.
# With this definition we force the ABI version to be unique and not risk crashes on different modules.
# (workaround for RS5-10582; see also https://github.com/pybind/pybind11/issues/2898)
add_definitions(-DPYBIND11_COMPILER_TYPE="_librs_abi")
include_directories(${CMAKE_BINARY_DIR}/third_party/pybind11/include)

pybind11_add_module(${PROJECT_NAME} ${SOURCE_FILES} ${HEADER_FILES} ${PYBIND_FILES})

/third_party/pybind11/

#  minimum required cmake version: 3.1.0
cmake_minimum_required(VERSION 3.1.0)

project(pybind11-download NONE)

include(ExternalProject)
ExternalProject_Add(
        pybind11
        PREFIX .
        GIT_REPOSITORY "https://github.com/pybind/pybind11.git"
        GIT_TAG "914c06fb252b6cc3727d0eedab6736e88a3fcb01" # 2.9.2
        SOURCE_DIR "${CMAKE_BINARY_DIR}/third_party/pybind11"
        # Override default steps with no action, we just want the clone step.
        CONFIGURE_COMMAND ""
        BUILD_COMMAND ""
        INSTALL_COMMAND ""
)

[henryiii]

But this is already at https://github.com/pybind/pybind11/blob/0964a9093a728dbf67b9b98c6371752b1a346f25/tools/pybind11NewTools.cmake#L35 ?

[stridera]

Yeah, I noticed. I"m not a master at cmake files so I didn't just do a pull request, but I know that I'm getting the Unknown CMake command "python3_add_library". in my project until I add that line in my own branch. My guess is because it's inside the function, it's not calling any of the lines outside that function.

[BeatWolf]

Using windows and python 3.11 i seem to have a similar issue. python3_add_library is not found. The proposed solution here gets me a little farther, does not solve it yet though (different error).

[luator]

Are there any new insights on this? I just ran into the same error after upgrading my build environment from Ubuntu 20.04 to 22.04. So I guess it is related to the Python and/or CMake version.

[luator]

I found some workaround: In my case the error was triggered because I did find_package(pybind11) after an other package that apparently also searches for Python (Python3_FOUND was true) but probably in an incompatible way. Simply moving pybind11 to the top of the find_package-list fixed it for me.

[henryiii]

If you are searching for Python multiple times, you might want to set Python_ARTIFACTS_INTERACTIVE. Otherwise, FindPython will search every single time, and can even find different Python versions.