undefined reference with multiple names .ccp file in different folders

[NicoHood]

There we go! Found a "better" bug finally :)

If you have a library structure like this:
/src/folderA/file.cpp
/src/folderB/file.cpp

You will get compile errors, even if the .cpp file (with the same name) just exists (empty):

Arduino/sketchbook/libraries/HID-Project/src/MultiReport/../HID-APIs/GamepadAPI.hpp:38: undefined reference to `Gamepad'
[more of them...}

Commit can be found here:
NicoHood/HID@6d6c7d3

This PR is required to build the Gamepad example without (other) compile errors:
arduino/Arduino#3948

So it looks like the builder does not differentiate between folders.

[matthijskooijman]

Weird, I thought we fixed this by keeping the library directory structure intact, but perhaps this wasn't copied over to the arduino-builder code?

Could you post a full verbose compilation output?

I suspect that this is a limitation of gcc-ar / .a files. If I read the ar manpage right, files inside an archive are by default identified by just their filenames, no path included. It seems there is a non-standard extension to use the full pathname, but gnu ar only supports reading such files, not writing them. Perhaps using compiler.ar.flags=qc (using quick append, rather then replace) might help, though I'm not sure how the linker then treats this archive.

[ffissore]

@NicoHood can you pls provide full debug output?