Multiple Rust modules with "cargo test" (minimal example included)

[SanderVocke]

Hi there,

I am starting to get the hang of using cxx-qt and would love to use it to slowly migrate a QML project's custom QML types from PySide to cxx-qt.

In my approach I compile the cxx-qt QObject types into a static library, then link that into a dynamic library with a registration function that registers them through qmlRegisterType.

It seems to work nicely.

However, I also would like to make use of cargo test to unit-test the objects on the Rust side individually. For my first module, this worked fine. But when creating more than one Rust module in the same crate, I run into linker errors.

To illustrate I made this minimal example: https://github.com/SanderVocke/cxx-qt-multi-module-problem

It is quite straightforward - basically it is the minimal-qml example, plus:

• a single C++ header for creating unique pointers, to use in unit-testing;
• an extra module added;
• each module exposes test functions with Cargo's test macros.

cargo build works fine, but cargo test runs into linker issues. The README gives more detail. This is on 0.6.1.

Would you have any idea how to modify or restructure this? Ideally I would still like it to be a single crate, because I expect to make many QObject derivatives and a crate per object would be overkill.

Thanks in any case!

P.S.: if with a small modification this structure can be made to work, I would suggest adding something like this into the examples folder.

[ahayzen-kdab]

It could be that both modules are outputting to the same header file?

Could you try using cxx_file_stem to specify different files in the bridge macro?

See the book for more info https://kdab.github.io/cxx-qt/book/bridge/index.html#cxx_file_stem

[LeonMatthesKDAB]

Just tested it locally: This solves the issue for me!
We probably need a better error message for this!

[LeonMatthesKDAB]

At least with the newest version of CXX-Qt (I bumped it to the version in our git repo)

[ahayzen-kdab]

Yeah, maybe the new build system can detect that, but it's figuring out if the existing file is from a previous build or if it's from a another module.

Or might just be that CxxQtBuilder needs to keep track of the output files and detect duplicates etc.

[SanderVocke]

Ah, that's probably it. I didn't realize the module name influenced this. Will try this, thanks!

[SanderVocke]

That's it, thanks! Each bridge module name should be different.