Change default CMake version, Ubuntu 14.04

Question

As far as I've understood, I need to use at least CMake 3.1 in order to use C++11. Ubuntu 14.04 comes with 2.8.x.

I followed a guide suggesting that one should install CMake to /opt, so I have CMake installed to /opt/cmake-3.2.1-Linux-x86_64 and added /opt/cmake-3.2.1-Linux-x86_64/bin to path (as the first element) in .bashrc.

If I try to apt-get remove cmake the process wants to remove not only CMake but also ROS (so yes, I've stopped by ubuntu: upgrading software (cmake) - version disambiguation (local compile), only to conclude that I couldn't use the answers)

Result of cmake --version:

cmake version 3.2.1

Setting minimum required version to 3.1 and running catkin_make in the same terminal yields:

CMake 3.1 or higher is required.  You are running version 2.8.12.2

How can I make catkin use the new (/correct) version of CMake?

Answer 1

Two things going on here:

1. According to the catkin_make file, it isn't copying the shell environment to the python subprocess 'cmake' invocation.

catkin_make:

...
if args.no_color:
    run_command(cmd, build_path)
else:
    run_command_colorized(cmd, build_path)

builder.py:

def run_command(cmd, cwd, quiet=False, colorize=False, add_env=None):
    ...
    env = None
    if add_env:
        env = copy.copy(os.environ)
        env.update(add_env)
    try:
        proc = subprocess.Popen(
            cmd, cwd=cwd, shell=False,
            stdout=stdout_pipe, stderr=stderr_pipe,
            env=env
        )

You can modify the appropriate lines in the catkin_make script to properly pass an empty dictionary for add_env, and it should attempt to copy the environment to the spawned sub process:

if args.no_color:
    run_command(cmd, build_path, add_env={})
else:
    run_command_colorized(cmd, build_path, add_env={})

This should modify the path and let it find the appropriate cmake version, but I'm not sure this alone solves your original question, leading us to...

2. If you are just attempting to use C++11 when building catkin, you could also just add the -std=c++11 compiler flag to CMAKE_CXX_FLAGS:

catkin_make --cmake-flags "-DCMAKE_CXX_FLAGS=\${CMAKE_CXX_FLAGS};-std=c++11"

or modify the CMakeLists.txt: set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")