How can I have code in a project that won't compile for Arduino?

Question

I want to test the algorithms in my code without needing to send it to an actual Arduino board. I figured I could lay out my project like:

project/
 core.cpp # core algorithms
 core.h # header for core.cpp
 project.ino # Arduino setup() loop() calling into core
 pc-main.cpp # main(argv) calling into core

However, when I do this, the Arduino IDE wants to compile pc-main.cpp, which won't work since it uses stdio and all that. What can I do instead?

Is there a way to hide a file from the build, other than changing the extension which would inconvenience other editors and compilers? Is there a different standard approach to this kind of problem?

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What I've thought of:

• I could put pc-main.cpp in another directory and have the build for it refer to the files in the Arduino project directory, but that seems awkward and I'd like a more elegant solution.

• I could symlink the core.* files into the Arduino project directory from elsewhere, but that would also be inelegant, and inconvenience Windows users should one want to compile the project.

• I could put an #ifdef around the contents of pc-main.cpp, but I haven't found a suitable #define to check for, other than board-specific ones.

I don't want a solution which requires extra steps for each build; the whole point of trying to do this is fast and easy development.

I would also prefer one which does not bring in a whole additional build system, testing framework, or IDE; for example, I found arduino_ci and PlatformIO while researching this question. I'll switch to looking at such options if there isn't a good solution to the problem as I've stated it here.

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[My question is arguably the same as Project structure to build for PC and Arduino at a high level, but the question and answer there are broad and about organizing modules and not how to make the build actually work.]

Answer 1

I would use conditional compilation, like this:

#ifndef(ARDUINO)
// Non-Arduino code.
#endif

• Kevin Reid: Thanks. Is there official documentation that specifies this #define exists?
• JRobert: You can add the #define to your code and manually change it when you change environments. You can look up Arduino compiler predefined symbols. Or you can tweak the IDE's compiler command to include "-DSYMBOL_OF_MY_CHOICE" which would define your symbol during an IDE compile and presumably be undefined in your desktop environment.
• Kevin Reid: To be clear, I found that ARDUINO is already defined and I didn't need to configure anything, so Edgar's code works exactly as written. I'm asking if there's documentation for it, as I think the answer would be even better with a link.
• Edgar Bonet: @KevinReid: I didn't find it in a doc (although it's mentioned here), but in a Makefile intended to emulate the Arduino IDE.