scikit-build
cmake only runs make single-threaded (-j1)
Problem:
When I run the cmake pypi package version from catkin, I get the following warning in the logs:
make: warning: jobserver unavailable: using -j1. Add '+' to parent make rule. which means nothing is built in parallel.
Also, CMake calls make with -j1, and the build is thus single-threaded.
Expected behavior:
cmake runs with job setting from catkin, which would result in a multi-threaded build (-j12). This is what happens when using a CMake .deb package installation.
Analysis:
This only occurs when CMake is installed via pip. The problem with that is that in this case the entrypoint to CMake (/usr/local/bin/cmake) is a Python file which then subprocess.calls the actual CMake binary. However, since Python 3.2, file descriptors are not forwarded to child processes anymore by default and therefore the real CMake (and therefore also make) cannot access catkin's make jobserver and defaults to -j1. (see: https://docs.python.org/3/library/subprocess.html "Changed in version 3.2: The default for close_fds was changed from False to what is described above.". )
System:
- Ubuntu 20.04 LTS
- catkin_tools 0.8.5
- Python 3.8.10 (default, Jun 22 2022, 20:18:18) [GCC 9.4.0]
- cmake==3.23.3
