Hopefully better cross-compiling support with Python #1684
Conversation
CMake historically has had issues with finding dependencies for the target system and the host system in the same project. vcpkg has its own concept of host dependencies, but that doesn't generalize to the rest of CMake. In Plasma's case, the only host dependency that is causing is pain is the Python interpreter, to run the resources.dat building step on the host at compile time. CMake 4 introduces the idea of Python artifact prefixes, to allow finding Python multiple times. They give cross-compiling and needing the host interpreter as an example of where this is useful (although it's unclear to me how exactly it's told to find the host interpreter vs the target interpreter). This change should allow us to opt-in to the prefixed behaviour on CMake 4, while retaining the existing behaviour on CMake 3 with a conditional assignment to the prefixed executable variable.
|
I assume this would also need some vcpkg adjustments (once that supports CMake 4.0) to differentiate between host and target dependencies? As I understand it, part of the issue is that some of the dependencies (specifically |
|
yeah, vcpkg.json does currently specify that it wants But there are definitely some vcpkg/CMake 4 things to sort out before this is ready to go. I'm not happy with the CMake 4 version checks I had to add here, but vcpkg was doing weird stuff when asked to find the interpreter 😕 |
CMake historically has had issues with finding dependencies for the target system and the host system in the same project. vcpkg has its own concept of host dependencies, but that doesn't generalize to the rest of CMake.
In Plasma's case, the only host dependency that is causing is pain is the Python interpreter, to run the resources.dat building step on the host at compile time.
CMake 4 introduces the idea of Python artifact prefixes, to allow finding Python multiple times. They give cross-compiling and needing the host interpreter as an example of where this is useful (although it's unclear to me how exactly it's told to find the host interpreter vs the target interpreter).
This change should allow us to opt-in to the prefixed behaviour on CMake 4, while retaining the existing behaviour on CMake 3 with a conditional assignment to the prefixed executable variable. In my testing with cross-compiling for Windows, it does seem to actually find the right values when using CMake 4.
Note: We can't adopt CMake 4 in CI until vcpkg properly supports it. They seem to be doing a bunch of work around that right now.