Passing (a lot of) variable(s) values at build time

[samatthias]

Dear Community,

I’m researching quite a while now for getting into the secrets of passing some variable values at build time. Here was a thread that I walked through but I’m not satisfied yet. These values are not for public sharing i.e. if you want to share your code online on github or similar services (secrets, ips, URLs, etc.pp.)

Thread I studied:

Pass env variables at build time

Hello, I am working on an open source project which however connects to some private cloud service. I want the DSN string for the service (mqtt) to be “added” at build time, so my code on github doesn’t expose any credentials. Any idea how to achieve this? Also, I see that even when working on arduino, I am not handling a .ino file anymore but a .cpp one. Can I use regular cpp syntax in platformio or am I still constrained to the C-like arduino language? Thank you!

There are still some questions i.E:

• I have tons of variables in my main.cpp file like (IPAdress, subnet, gateway, secrets like passwords, URLs, etc. pp.) - shall I really add these all to my platformio.ini file (as suggested as dynamic build flags)? In my opinion, it would be great if I could put them into one separate file in my project. Is this feasible? Is there a better solution to this problem I’m not aware of? Is there a better best practice?

• Anyhow - if I go with the proposed solution of the mentioned thread I can’t share my platfomio.ini file anymore on github (if add it to the gitignore file) - isn’t that bad practice?

Could one of you spend a little bit of time to answer my questions?

Thanks and best regards
Matt

[maxgerhardt]

@samatthias

In my opinion, it would be great if I could put them into one separate file in my project. Is this feasible? Is there a better solution to this problem I’m not aware of? Is there a better best practice?

So, just a .h header file then that is git-ignored or only filled with example values? Like in WifiMQTTManager/examples/Basic at master · dreed47/WifiMQTTManager · GitHub? That works.

@samatthias

Anyhow - if I go with the proposed solution of the mentioned thread I can’t share my platfomio.ini file anymore on github (if add it to the gitignore file) - isn’t that bad practice?

In the special case that the platformio.ini just uses build flags with the reference to the environment variable names, it wouldn’t contain any secrets.

[samatthias]

@maxgerhardt: Many thanks for bringing light into this. Pretty easy solution. Thanks!

@maxgerhardt

In the special case that the platformio.ini just uses build flags with the reference to the environment variable names, it wouldn’t contain any secrets.

Ok, then I don’t understand where the values of these are stored. Can you clarify that?

Best regards
Matt

[maxgerhardt]

@samatthias

Ok, then I don’t understand where the values of these are stored. Can you clarify that?

In the environment variables themselves. This is a very special and you should probably do the .h header file way.

When your platformio.ini is setup e.g. like

build_flags = -D WIFI_PASSWORD=${sysenv.ENV_WIFI_PW}

all this does is to say "fetch the current value of the system environment variable ENV_WIFI_PW and put it in the C/C++ macro WIFI_PASSWORD. A user would then still have to execute

export ENV_WIFI_PW="abcdefgh"

(command depending on the OS used)

to fill it with a concrete value.

Thus you can also see that an editable file is much easier to work with.

[samatthias]

@maxgerhardt: Ah ok, from system vars - no you’re absolutely right, that’s not what I want. But many thanks for your clarifications. Very nice explanations!

Have a nice time!

regards
Matt