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# C++ files organisation

## 12 posts in this topic

I have been coding C++ for more than a year now and I just realized that the way I package my project is very different from how all the C++ open source projects package their projects.
Most of the C++ projects package in such a way that it looks like this

project
|_ include
|_ src

while I usually store them in deep folder structures.
project
|_folder A
|_ sub folder A
|_ sub folder B
|_ folder B

When I learn a language, I want to embrace it fully and not just use it like another language. But before I migrate some of my projects, I thought I asked, what are the advantages/disadvantages to doing either way ? I know my way probably came from back when I just started programming and Java has a really deep folder structure. Do anyone do the same as I ?

Edited by ZwodahS
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Putting header files into a include folder has the advantage that you have all interfaces to your modules in a single place, like /usr/include and /usr/local/include on UNIX style systems. To make the software available to others, maybe as a library gives you a  more simple way to find the header files to the libraries.

But at the end I suspect that it is up to your personal feeling about how to handle header files.

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Nested source layout seems to have two problems:

1) Includes may have to still be relative i.e #include "../../player/LeftHand.h" which may get a little bit messy and a pain if you decide to move the project structure.
2) At work when we used Unity we had an issue with locating scripts (quickly). A location that makes sense to one person does not to another. We decided to have all game script files in the same directory, all library scripts in their own directory. So much easier.

Note that Visual Studio provides structures in the IDE call "filters". Even though these appear to be nested, they only point to files which are all in the same directory. This may be the best of both worlds.

I recommend nesting source only if they are unique to a lib or .exe such as

mygame
- bin
- game.exe
- lib
- libplatform.a
- libnetcode.a
- src
- platform
- *.cpp *.h
- game
- *.cpp *.h
- netcode
- *.cpp *.h
- *.cpp *.h

And then -Isrc/platform -Isrc/netcode -Isrc/imageloader so that library headers can be included using < >. Edited by Karsten_
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Personally I'm never putting my headers into a different directory. The only point to do that would be for publishing just the headers for a library I want to publish, but I would rather use CMake or some other build tool to copy the relevant headers from the source directory to a published include directory when needed.
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1) Includes may have to still be relative i.e #include "../../player/LeftHand.h" which may get a little bit messy and a pain if you decide to move the project structure.

I would suggest to not include files relative to the location of the source file or whatever, that is just asking for trouble in my opinion. Always include files from a base relative directory (e.g. project root, or more likely the "include" folder) and the problem disappears.

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Using relative includes is a good choice to prevent many -I<include dir> compiler parameters. This way you can go inside a subdir with sources and start the compiler/make in there without thinking about where you are and how your compiler include parameter must look.

But... in fact it is awesome to handle if you move a module around.

Because I use UML with a code generator that produces the include statements I do not think about the positioning. It is always right and works, even if I move around the modules in the model.

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Wow that is a lot of feedback :P. Thanks a lot.

1) Includes may have to still be relative i.e #include "../../player/LeftHand.h" which may get a little bit messy and a pain if you decide to move the project structure.

I would suggest to not include files relative to the location of the source file or whatever, that is just asking for trouble in my opinion. Always include files from a base relative directory (e.g. project root, or more likely the "include" folder) and the problem disappears.

So instead of relative includes, what would be a good way if I don't want a centralized include folder ?

I have this problem recently when I was reorganizing my files and I need to update quite a few of the includes.

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Using relative includes is a good choice to prevent many -I<include dir> compiler parameters. This way you can go inside a subdir with sources and start the compiler/make in there without thinking about where you are and how your compiler include parameter must look.

I would avoid relative includes if at all possible and rather use something like CMake to generate my makesfiles then.
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Avoiding lots of search pathes on the command line has the benefit that it is clear what version of a header file is used and you need not read hundreds of -I parameters with long pathes to find at which point something goes wrong.

But as I already said. It is always alot of work if you move a module around.

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So instead of relative includes, what would be a good way if I don't want a centralized include folder ?
I have this problem recently when I was reorganizing my files and I need to update quite a few of the includes.

Unless you are making reusable libraries as part of your project, I would recommend a single folder for both your src and header files. i.e a single .exe means I would create a single src directory. If you find this folder simply has too much source code files in, then this might even suggest that you need to break your project up into multiple separate libraries (in which case they would get their own src directories (containing .cpp and .h).

So since these libraries and binaries are separate projects, you could say that I don't do any nesting in my projects. Some places where you may be tempted however is if some code is completely standalone from the rest of the project (i.e so no #include "../" needed since it has no dependence on other headers). If a part of a project is also in a separate namespace then you may also want to nest, however often parts in a nested namespace still require ../headers and I do typically try to avoid this pattern.

One system that I have found to be very effective is the following (I use cmake but this should work with many build systems). Imagine a folder structure as follows:

proj/
src/
game/
foolib/
barlib/

If I specify on the command like -Isrc, this means that anywhere in the game source code, I can do

  #include <foolib/foolib.h>

If foolib has a dependency on barlib, I can do in the foolib code:

  #include <barlib/barlib.h>

This means that you can separate your project into logical libraries (and separate .cpp / .h directories) and yet still be able to reference the correct headers you need.

Whats quite useful about this system is that if barlib was really made to be a standalone library, I could have an installer script like:

# mkdir /usr/local/include/barlib
# cp -r src/barlib/*.h /usr/local/include/barlib
# cp lib/barlib.a /usr/local/lib/

And now any project on my computer can access the barlib.h in exactly the same way as when it was part of my project. Edited by Karsten_
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Avoiding lots of search pathes on the command line has the benefit that it is clear what version of a header file is used and you need not read hundreds of -I parameters with long pathes to find at which point something goes wrong.

Well, in general I set exactly one include directory for my project (excluding 3rd party libraries). Every file can then simply include what it needs using <mytool/file.h> or <mylibrary/file.h>. CMake just simplifies doing that because every sub-makefile is aware of that include directory without any work on my part. An added benefit is that you immediately see which library/subproject an include is from.
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