[LLVMdev] Long-Term Support for LLVM Projects Extension to Build System?

[Chandler Carruth]

On Thu, Jun 18, 2015 at 5:50 PM Hal Finkel <hfinkel at anl.gov> wrote:

> This is also related to the metapoint that the cmake build system doesn't
> glob for source files (or anything else), unlike the makefile build system.
> This is understandable given the constraints, but we might want to restore
> some of that functionality for the purpose of supporting out-of-tree
> projects.
>

I actually think these are completely separate. See below.


>
> What I mean specifically, is that, for example, we could have a
> normally-empty directory tools/extensions, and tools/CMakeLists.txt could
> glob for directories in tools/extensions and call
> add_llvm_tool_subdirectory on all of them. It is true that you'd need to
> re-run cmake whenever you added something there (we could have a README in
> that directory to remind people of that), but that seems like a much
> smaller price than having to maintain a patched version of the upstream
> sources.
>

We already do this in numerous places. See projects/CMakeLists.txt which
does exactly this.

We don't automatically support external projects *in different locations*
through globbing, but that's because that doesn't make any sense.

We can add globbing-based recursion to subproject CMake files anywhere it
is useful.

There is no problem with globbing to add subdirectories IMO because
subdirectories *with new CMake files* clearly have to be introduced and
maintained at the points you run the 'cmake' tool. Only globbing for
*source files* seems problematic to me at all.

-Chandler
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