[PATCH] D10665: [CMake] Cleanup tools/CMakeLists.txt to take advantage of the auto-registration that was already partially working.

[Chris Bieneman]

CMake has no mechanism for cache invalidation. Unless we all start writing perfect forward-looking code the first time, every time we're going to have to accept that sometimes the CMakeCache will need to be deleted if you go backwards or forwards by large increments.

In this case, when I first found the caching issue I landed a patch to cleanup the caches on builders and developer machines so that everyone didn't need to delete their caches. I think that is the best we can expect. I don't think it is reasonable to expect that you'll never have to delete your CMakeCache or even the whole build directory.

There should be no problem walking back in revisions with my patch, but walking forward if you jump over the patch that I landed to clear out the cache (which sat in tree for a few days) you will need to delete your cache. Re-generating the cache is quite fast, and some of our bots (specifically the Jenkins ones) even do it on every build.

-Chris

> On Jul 24, 2015, at 4:48 PM, NAKAMURA Takumi <geek4civic at gmail.com> wrote:
> 
> 
> chapuni added a comment.
> 
> This makes harder for walking revisions before r242059.
> I think it'd be really bad idea to require removing CMakeCache.txt.
> 
> Chris, could you consider how to satisfy build tree before r242059?
> 
> 
> Repository:
>  rL LLVM
> 
> http://reviews.llvm.org/D10665
> 
> 
>