r190560 - [CMake] Fix repository version checking dependencies harder.

[Jordan Rose]

On Sep 12, 2013, at 8:31 , Argyrios Kyrtzidis <akyrtzi at gmail.com> wrote:

> On Sep 11, 2013, at 7:32 PM, David Majnemer <david.majnemer at gmail.com> wrote:
> 
>> This commit causes no-op builds to relink which is slow. Why was this changed in the first place?
> 
> Yes, I find this awful. Why don't we generate a temporary file and replace SVNVersion.inc only if it is different ?

I tried several things here, but the underlying issue is that CMake doesn't know to do some action before recalculating dependencies. That means that if you update your repository and it doesn't touch any files in clangBasic, you get an updated SVNVersion.inc but not a rebuilt Clang. It's only on the next build that the change will be picked up, at which point you've already realized the problem.

I can add a guard option that turns this behavior on and off, but I couldn't think of a better answer that would just work.

Jordan

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