I have the following problem:
We use cmake unity build in our project in batch mode.

set_target_properties( ${target} PROPERTIES UNITY_BUILD ON UNITY_BUILD_MODE BATCH )

Mostly it all goes well, but in some projects unity batches are regenerated every cmake launch, which leads to recompiling them even though source files weren’t changed.

I checked the content of unity files, it also remains the same, so it isn’t some source sorting issue. In cmake trace-expand, I wasn’t able to find anything about unity files. Why can such thing happen and how can I find, why are those files regenerated every time?