How to collect source files with CMake without glo

Question

The CMake documentation explicitly states that file(GLOB ...) is not recommended to collect source files for a build, but it doesn't mention what the recommended method actually is.

Specifying every source file manually sounds a little bit too manually to me. So, what is the right method to collect source files, if not file(GLOB ...)?

Answer 1

I use a conventional CMakeLists.txt and a python script to update it. I run the python script manually after adding files.

import os
import re       

def relFiles(base, sub):
    fullSub = os.path.join(base,sub)
    abs = [os.path.join(dp, f) for dp, dn, fn in os.walk(fullSub) for f in fn]
    return [os.path.relpath(f, base) for f in abs]

def updateAddLibrary(cmakelistsDir, subs):
    cmakelists = os.path.join(cmakelistsDir, "CMakeLists.txt")
    listings = [relFiles(cmakelistsDir, sub) for sub in subs]
    files = [f for listing in listings for f in listing] #flatten
    with open(cmakelists, 'r') as file:
        text = file.read()
    sources = "".join(["    %s\n" % f.replace('\\', '/') for f in files])
    text = re.sub(r"add_library\s*\(\s*([^\s\)]+).*?\)",
           r"add_library(\1\n%s)" % sources, 
           text, 1, re.DOTALL)
    with open(cmakelists, "w") as file:
        file.write(text)

dir = os.path.dirname(os.path.abspath(__file__))
updateAddLibrary(dir, ['inc','src'])

Example before:

...
add_library(MyLib
    inc/a.h
) 
...

after:

...
add_library(MyLib
    inc/a.h
    inc/sub/b.h
    src/a.cpp
)        
...

Answer 2

Manual is indeed the recommended method. By recommending against using GLOB, the documentation is simply warning against a build system that depends on files present. For example, you want to add a test executable, so you create mytest.cpp. Oops. Now your library compilation breaks. The documentation for AUX_SOURCE_DIRECTORY (similar purpose as globbing for for source files) gives the following warning:

It is tempting to use this command to avoid writing the list of source files for a library or executable target. While this seems to work, there is no way for CMake to generate a build system that knows when a new source file has been added. Normally the generated build system knows when it needs to rerun CMake because the CMakeLists.txt file is modified to add a new source. When the source is just added to the directory without modifying this file, one would have to manually rerun CMake to generate a build system incorporating the new file.

If you're certain that you want all the contents of a directory, and don't plan on adding new ones, then by all means use a GLOB.

Also, don't forget listing files manually doesn't have to involve typing all the filenames. You could do, for example, ls *.cpp >> CMakeLists.txt, then use your editor to move the list of files to the correct place in the file.

Answer 3

I use GLOB for exactly that and every time I add a file I run

touch ../src/CMakeLists.txt

The next make command will re-scan the directories.

"There is no way for CMake to generate a build system that knows when a new source file has been added" Really? Okay, so tell it!

It's not 100% automatic but a damn sight easier than adding files manually.

Answer 4

I use cog, a python module. Here is a sample to collect .cpp file:

The CMakeLists.txt:

set(SRC_FILES "")

# [[[cog
#    import cog, glob
#    for src in glob.glob('*.cpp'):
#       if "skeleton" in src: continue
#       cog.outl("SET(SRC_FILES ${SRC_FILES} %s)" % src)
# ]]]
# [[[end]]]

add_library(mylib STATIC  ${SRC_FILES})

And then, run:

python -m cogapp -r CMakeLists.txt

The CMakeLists.txt file will be updated in place.

For how to install cog and other usage, please read the article from the author.