compile-sketches uses gnu++11...

[FredM67]

Describe the problem

My sketches need to set gnu++17 instead of gnu++11 in the platform.txt file.

How to do the same when compiling on GitHub?

To reproduce

Compile some sketches with a c++17 feature, not available in c++11.

Expected behavior

It should be possible to overwrite the c++ version used to compile.

'arduino/compile-sketches' version

latest

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest version
• My report contains all necessary details

[per1234]

Hi @FredM67. You can add arbitrary flags to the arduino-cli compile command used to compile the sketch via the action's cli-compile-flags input:

https://github.com/arduino/compile-sketches#cli-compile-flags

You can learn the available flags from the Arduino CLI documentation:

https://arduino.github.io/arduino-cli/latest/commands/arduino-cli_compile/#options

In this case, the flag of interest is --build-property. Depending on which boards platform you are using, you may be able to use the compiler.cpp.extra_flags build property to add additional flags to the compilation command. So if you wanted to add the -std=gnu++17 flag to the compilation command, you would add this to your workflow under the with key of the step that runs the arduino/compile-sketches action:

cli-compile-flags: |
  - --build-property
  - compiler.cpp.extra_flags=-std=gnu++17

Please note that usability of build properties is dependent on how each boards platform author has configured their platform. Providing customization of the compilation command via compiler.cpp.extra_flags, etc. build properties is a common convention established by Arduino's official boards platforms, but there is no guarantee of that. Some platform authors have also unnecessarily used the properties for their own purposes (arduino/arduino-cli#846). So this is an advanced usage and you should make sure to study the boards platform to make sure it supports this.

[FredM67]

cli-compile-flags: |
  - --build-property
  - compiler.cpp.extra_flags=-std=gnu++17

Thx a LOT for the example.... I've tried every possible combinaison, but couldn't find the right way to add this flag.
I think, a sample should be added to the doc !

[per1234]

You are welcome.

I completely agree that the general usage of this input is not adequately documented. A pull request adding an example. I would not use something so complex as --build-property, but I do think demonstrating the correct way to pass flag that have an argument is important. So I think the best candidate for the example would be --output-dir