How to include a header file when the file that is including it is not in the root project folder?

Question

I am trying to learn how to better organize a project and it's files in C++.

My simple test project only seems to work whenever main.cpp (and main.exe) is in the root project folder. Here's how I wanted to try to set it up.

• Project
  • .vscode
    • c_cpp_properties.json
  • headers
    • header.h
  • main
    • main.cpp
    • main.exe

Inside of main.cpp, I have #include "headers/header.h"

When I try to compile it with this setup, I get this error fatal error: headers/header.h: No such file or directory

I am wondering why this doesn't work when the following setup, which doesn't have main.cpp in a subfolder, compiles and runs just fine (without changing any of the code).

• Project
  • .vscode
    • c_cpp_properties.json
  • headers
    • header.h
  • main.cpp
  • main.exe

I am using Visual Studio Code with the C/C++ and C/C++ Compile Run extensions (in case that's relevant).

Edit:

Changing it to "../headers/header.h" does work, but I am wondering how I would do this without using ../.

If I'm understanding correctly I just need to add something to the includePath in c_cpp_properties.json. Here's what the "includePath" section looks like right now.

"includePath": [
    "${workspaceFolder}/**"
],

So I think I just need to make it something like

"includePath": [
    "${workspaceFolder}/**",
    "..."
],

What exactly should I be putting in the ... part?

Answer 1

When compiling a specific file, your compiler will look at the path of this file. So, in your first example, it is .../Project/main/main.cpp, but in your second example it's ../Project/main.cpp. So now its obvious why looking at the path that is headers/header.h is valid in second case, but not the first one.

However, you can of course leave your main.cpp in your main directory if you wish, you'd only need to set INCLUDE_PATH directory. If you were using Makefile, it'd be a simple -I flag addition, but since you're using VS code, you might want to look at this question. Sorry I can't provide more detailed solution, I'm not really familiar with VS Code environment.