How to have CMake resolve directories

Usage
1

Currently, I have to add directories to my files in my C/C++ project both in the CMakeLists.txt and my include directives, for example:

add_library (library1
src/dir1/file1.h
src/dir1/file1.c
)

and in file1.c itself:

#include “…/dir2/fileNeededByFile1.h”

etc.

I’d like CMake to resolve this for me automatically. I thought that the “include_directories” would do this, but it seems to not be the case. How can I tell CMake to look into certain directories (recursively, or if not possible, not recursively) and avoid having to write the directories one by one?

2

I’m really unclear on what you are asking for.

This article does a pretty good job explaining include directories with CMake though.

3

Thanks for the link, I will check it.

What I want is to not have to write the directory of every file both in the add_library add_executable etc. commands and the include directories in the code, as I surmise that CMake likely offers me a way to solve this. That is, instead of

add_library (library1
src/dir1/file1.h
src/dir1/file1.c
src/dir2/file2.h
src/dir2/file2.c
…
)

I’d like to be able to write:

add_library (library1
file1.h
file1.c
file2.h
file2.c
)

and in file1.h’s directives, instead of
#include “…/src/dir3/fileNeededByFile1.h”.

I’d like to write
#include “fileNeededByFile1.h”.

I expect that there is a

command_to_set_directories( library1
src/dir1/
src/dir2/
src/dir3/
}
to do that.

4

There isn’t a CMake command that auto resolves directories the way you want.

Your best tools for adding files and include directories are target_sources / target_include_directories

I’d look at this blog post by Craig Scott for handling your source files in a nice way which I have seen accepted in many projects that want to make their CMake code nicer.

Essentially your CMake script would end up looking like this:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.13)

project(FOOBAR LANGUAGES C)

add_library(library)
add_subdirectory(src)
add_subdirectory(inc)

Overall I think that’s a nice presentation :+1:

Then you have a CMakeLists.txt in src that looks like this (You can obviously do this for as many directories as you want):

# src/CMakeLists.txt
target_include_directories(library PRIVATE .)
target_sources(library PRIVATE 
     file1.c 
     file1.h
     file2.c
     file2.h
)

And potentially if you a nice library author your CMakeLists.txt in your inc directory looks like this:

# inc/CMakeLists.txt

# Notice the use of PUBLIC!
# Now when a client links against your library they automatically absorb the inc/ include directory
# Which makes their CMake code nicer since they don't need to know how your project is laid out!
target_include_directories(library PUBLIC .)
target_sources(library PRIVATE
    library1.h
)
5

That looks nice. Thank you so much.

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