Ninja support for CLion IDE

CLion_Ninja.md

Ninja support for CLion IDE

This script enables Ninja-powered builds in CLion IDE by wrapping around CMake, which it uses. See my blog post for details.

Disclaimer

This script is provided AS IS with no guarantees given or responsibilities taken by the author. This script relies on undocumented features of CLion IDE and may lead to instability of build and/or IDE. Use it on your own risk under WTFPL terms.

Getting started

Supported OS: I've tested this scipt under Ubuntu and python 2.7. I suppose it should work on Mac and Windows too but I've never tested it.

0. Make sure you have python 2.7 installed.
1. Download cmake_ninja_wrapper.py and give it execution permission.
2. Edit REAL_CMAKE variable at the beginning of the script to point at CLion's bundled CMake binary (recommended) or at system CMake.
3. In CLion, go to Settings → Build, Execution, Deployment → Toolchains
4. Under "CMake executable" select cmake_ninja_wrapper.py script.

Make sure that CLion successfully detects make program (it should be still /usr/bin/make) and C/C++ compiler. At this point you are done. Go, reload you CMake project and try to build it.

Troubleshooting

In case of any troubles try setting TRACING variable at the beginning of the file to True and re-parsing CMake project in IDE. After that look at /tmp/cmake_wrapper.log for any insights :-)

cmake_ninja_wrapper.py

#!/usr/bin/python

import sys
import os
import subprocess
import shutil
import re
import select

# ---------------------- Configuration section ------------------------------

REAL_CMAKE = "/usr/bin/cmake"
TRACING = False

# --------------------------- Code section ----------------------------------

def trace(message, argv = []):
    if not TRACING:
        return

    with open('/tmp/cmake_wrapper.log', 'a') as log:
        if not argv == []:
            log.write("\n\n")

        log.write(message)

        if not argv == []:
            argv = '"%s"' % ('" "'.join(argv))
            log.write("\n\n\t%s\n\tat: %s\n" % (argv, os.getcwd()))

def call_cmake(passing_args):
    """Call real cmake as a subprocess passing it's output both to stdout and trace file."""
    passing_args = [REAL_CMAKE] + passing_args
    trace("Calling real cmake:", passing_args)

    proc = subprocess.Popen(passing_args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize=0)
    while True:
        reads = [proc.stdout.fileno(), proc.stderr.fileno()]
        ret = select.select(reads, [], [])

        for fd in ret[0]:
            if fd == proc.stdout.fileno():
                line = proc.stdout.readline()
                sys.stdout.write(line)
                sys.stdout.flush()
                trace(line)
            if fd == proc.stderr.fileno():
                line = proc.stderr.readline()
                sys.stderr.write(line)
                sys.stderr.flush()
                trace(line)

        if proc.poll() != None:
            break

    for line in proc.stdout:
        sys.stdout.write(line)
        trace(line)

    for line in proc.stderr:
        sys.stderr.write(line)
        trace(line)

    return proc.poll()

def is_real_project():
    """Detect if called inside clion private directory."""
    cwd = os.getcwd()
    return "clion" in cwd and "cmake" in cwd and "generated" in cwd

class CMakeCache(object):
    """CMake cache management utility"""
    def __init__(self, path):
        super(CMakeCache, self).__init__()
        self.path = path
    
    def alter(self, variable, value):
        """
        Change a variable value in CMake cache.
        TODO: Add variable if it doesn't already exist
        """
        if not os.path.isfile(self.path):
            return

        with open(self.path, 'r') as cache_file:
            cache_data = cache_file.read()

        pattern = '%s=.*' % re.escape(variable)
        replacement = '%s=%s' % (variable, value)
        cache_data = re.sub(pattern, replacement, cache_data)

        with open(self.path, 'w') as cache_file:
            cache_file.write(cache_data)

    def ninjafy(self):
        self.alter('CMAKE_GENERATOR:INTERNAL', 'Ninja')
        self.alter('CMAKE_MAKE_PROGRAM:FILEPATH', '/usr/bin/ninja')

    def makefy(self):
        self.alter('CMAKE_GENERATOR:INTERNAL', 'Unix Makefiles')
        self.alter('CMAKE_MAKE_PROGRAM:FILEPATH', '/usr/bin/make')

def ninjafy_argv(original):
    """Replace Unix Makefiles generator with Ninja"""
    processed = []
    next_g = False
    for a in original:
        if a == '-G':
            next_g = True
        elif next_g and 'Unix Makefiles' in a:
            a = a.replace('Unix Makefiles', 'Ninja')

        processed.append(a)

    return processed



trace('Originally called:', sys.argv)

# Enable wrapping logic only when called inside clion private directory.
if not is_real_project():
    sys.exit(call_cmake(sys.argv[1:]))

# Check if generator argument was specified
if '-G' in sys.argv:
    # Generate Makefile artifacts required by CLion
    cache = CMakeCache('CMakeCache.txt')
    cache.makefy()
    exit_code = call_cmake(sys.argv[1:])
    if exit_code != 0:
        sys.exit(exit_code)

    # Generate Ninja artifacts for actual build
    passing_args = ninjafy_argv(sys.argv[1:])
    cache.ninjafy()
    sys.exit(call_cmake(passing_args))
else:
    sys.exit(call_cmake(sys.argv[1:]))

Would it be too slow because of python?

Not in any noticeable way, I don't think. The script does some very lightweight string manipulation, which is fast enough in just about any language.

That said, it's been years since I've used this script myself, so please let us all know if it worked for you 😃