Please explain '-iwithprefixbefore' in 'includes.txt'

[oclyke]

Hi @facchinm (or others 🙂) - Inspired by this project I am trying to build a similar mbed-os core for the Apollo3.

I have faced an issue trying to supply additional include search paths to the compile steps in a portable (cross platform) capable way.

• Using the @file syntax from mbed's generated include directly won't work because those paths are relative and I can't guarantee the working directory that my compiler is called from (can I?)
• I've tried writing scripts to use the IDE's {runtime.platform.path} variable to generate a list of search paths that are absolute, however this bloats the number of characters from ~16k (mbed generated include file) to ~40k (varies based on the exact install location of the core) which causes an error running GCC. (~32k characters seems to be the limit for a single command line call)

At a loss I came back to this project for a reference. I see in your variant's includes.txt it has this leading -iwithprefixbefore/ and that it is directly included in your compile / link lines ("@{compiler.mbed.includes}" -> nano33ble.compiler.mbed.includes={build.variant.path}/includes.txt)

Can you please explain what that prefix is doing? How is it handled by the Arduino IDE?

Thanks a lot - I have been trying hard to determine a way to expose the full mbed API to the user in this core.

[facchinm]

Hi @oclyke !
That procedure takes advantage of https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html , so that paths length is greatly reduced (and can be specified as relative to {runtime.platform.path} ).
I think the missing piece you are looking for is "-iprefix{build.core.path}" ; in this way, gcc replaces internally the withprefixbefore string with the one provided.

Glad to hear you are working on the Apollo3! Let me know how it proceeds 😉

[oclyke]

Thanks a bunch @facchinm! I was previously unaware of that option in GCC. It will be invaluable in the project and future work as well. You can always check out the Apollo3 project here: https://github.com/sparkfun/Arduino_Apollo3

The v2.0.0 release will be based on mbed so that we can support ArduinoBLE as directly as possible.