[Lldb-commits] [PATCH] D65798: [lldb][CMake] Infer `Clang_DIR` if not passed explicitly

[Pavel Labath via Phabricator via lldb-commits]

labath added inline comments.


================
Comment at: lldb/cmake/modules/LLDBStandalone.cmake:6
+  # next to LLVM's module directory.
+  set(Clang_DIR ${LLVM_DIR}/../clang)
+  message(STATUS "Inferred Clang_DIR: ${Clang_DIR}")
----------------
sgraenitz wrote:
> compnerd wrote:
> > sgraenitz wrote:
> > > compnerd wrote:
> > > > What happens in the standalone clang build scenario?  Can I ask what is the motivation for this change?  I think it is better to require that the user pass the path, as that is an explicit dependency of LLDB.
> > > I don't think there's any side-effects on Clang standalone builds. Is that what you mean with "standalone clang build scenario"?
> > > 
> > > I would like top prevent people from writing custom build scripts on top of CMake. Passing a number of very similar paths to CMake, e.g. each time we want to generate a Xcode project for development, this option seems to become compelling quickly. This patch makes standalone configurations simpler. Basically, it provides a default value. I doesn't cut down functionality.
> > > 
> > > You can still explicitly pass any path you want. This branch will then not be taken.
> > I think that the build fragmentation has caused a larger problem, and I would like to avoid that.  The standalone build scenario is:
> > 
> > build/llvm
> > build/clang
> > build/lldb
> > 
> > In this case, `../clang` does not exist (`../../clang/lib/cmake/clang` does).  I think what I would suggest instead is adding a cache file that has the configuration parameters setup already.
> For the scenario you describe, can you point me to any documentation that describes it or a bot that builds it?
> 
> > I think what I would suggest instead is adding a cache file that has the configuration parameters setup already.
> 
> How would your cache file look like?
> For the scenario you describe, can you point me to any documentation that describes it or a bot that builds it?

I think a lot of linux distributions which want to provide llvm,clang,etc. as separate packages build in this way. And those that don't, they'd probably want to build it that way, but they can't do it because it doesn't work for them for one reason or another (the standalone builds are always a bit behind, because the devs usually just build everything monolithically). I know at least gentoo builds llvm, clang and lldb standalone. Maybe @mgorny has a better overview of what other distros do...


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  https://reviews.llvm.org/D65798/new/

https://reviews.llvm.org/D65798