Re: ccache

Mark Veltzer <mark-zMkqr+MLrVdAfugRpC6u6w@xxxxxxxxxxxxxxxx> writes:

> If you think that this does not take H files into consideration you are 
> wrong. As Muli rightly states ccache takes the output of gcc -M which means 
> the ENTIRE source that the compiler sees (H files and all AFTER 
> preprocessor). In addition, it also stores the flags used for the compilation 
> in the cache. I would rarely see a situation where you would say that YOU DO 
> want the object recompiled unless you switched compilers (I'm not sure but I 
> think that there are plans for ccache to store the compiler version too so if 
> you switch compilers it will detect it and not use the cache. Muli ?!?).

I know all that, and I wrote myself ccache worked on preprocessed
files. But what if for some reason I made the file dependent on
something that is not under the compiler's control - a file that is
not C. Then if that file changed, make would recompile, but ccache
would grab the existing object from the cache.

Why would I want that? For instance, because I would want a generated
compilation timestamp to change... I can't really think of good
examples, but ccache works, AFAIK, on the basis of MD5 of the
preprocessed C sources, and make can update the build on the basis of
timestamps of dependencies external to C sources as well.

-- 
Oleg Goldshmidt | ogoldshmidt-PAF1oyTKKOFOm2FXKvvI6EB+6BGkLq7r@xxxxxxxxxxxxxxxx 
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