[LLVMdev] Transitioning build to cmake

[Jeremy Huddleston Sequoia]

Sent from my iPhone...

> On Jul 24, 2013, at 12:40, Sean Silva <chisophugis at gmail.com> wrote:
> 
> 
>> On Wed, Jul 24, 2013 at 10:11 AM, Jeremy Huddleston Sequoia <jeremyhu at apple.com> wrote:
>> I recently took a stab at changing the MacPorts llvm-3.4 port from the configure-based build system to the cmake-based build system.
> 
> Thanks for working on this!

No prob.  Hopefully we can iron out these wrinkles.

>> 4) Building clang using installed llvm
>> 
>> It looks like there is some support for building clang against an installed llvm by setting CLANG_PATH_TO_LLVM_BUILD.  This fails miserably in part because the installed llvm cmake files reference build time paths, but even after fixing that, there are tons of build failures.  I'm guessing this is still a work in progress, but if I should file bugs, please let me know.
> 
> This is probably not a very good idea because clang evolves in lock-step with LLVM. Unless the installed LLVM is the same revision as the clang you are building,

They match revision.  We just need to split the build into two subports to break dependency cycles, and I'm hoping to avoid rebuilding the core libraries a second time.

> things are likely to not work due to internal API changes. The option you cite is more likely intended for when you build clang in a directory separate from LLVM (rather than when it is in llvm/tools/clang/, where things just work) but both are still checked out at the same revision.
> 
> -- Sean Silva
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