[cfe-commits] r159256 - in /cfe/trunk: include/clang/Basic/FileManager.h lib/Basic/FileManager.cpp

[Axel Naumann]

Hi Matthieu,

On 06/27/2012 07:18 PM, Matthieu Monrocq wrote:
> On Wed, Jun 27, 2012 at 4:15 PM, Axel Naumann <Axel.Naumann at cern.ch
> <mailto:Axel.Naumann at cern.ch>> wrote:
>     Okay. I see three maybe more reasonable options, in decreasing order of
>     preference for us:
>     * truncate the cache (we'd anyway only remove the last N files)
>     * add interface to decide which file should be cached and which
>     shouldn't, based on the file's full name, in our case we'd likely only
>     cache read-only files (e.g. STL).
>     * clear the cache altogether. That's the least performant option for us.
>
>     Should we implement the first option? Or keep the current version?
>
>     Cheers, Axel.
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>
> There has been a discussion about avoiding warnings in 3rd party headers
> on top of STL headers.

Sorry, I don't see yet how that's relevant here.

> In this case we could expect that Cling did the
> smart things and cached 3rd party headers but not local ones. Or perhaps
> had the ability to only clear ones "own" files.

Isn't that what I was suggesting as option 2? Are you saying that I 
missed an existing interface that enables selective caching?

>  From what I understood, in Cling you don't edit many files at once.
> However if we are talking about being able to react to a modification to
> a header file, without really knowing its dependencies, then the
> truncation cannot be used easily here it seems.

We would use truncation as a simplistic dependency analysis: any file 
that comes after might depend on the file that needs to be removed. The 
current trunk enables removal of a specific FileEntry. With that we 
could do more fine-grained analysis, a la include-what-you-use. And 
that's really our preferred choice.

Cheers, Axel.