[ccache] Support for -fprofile-generate, -fprofile-use, -fprofile-arcs

[Chris AtLee]

I've pushed some changes up here that I hope addresses all the comments:
https://github.com/catlee/ccache/compare/jrosdahl:master...catlee:profile


On Fri, Jul 22, 2011 at 3:19 PM, Chris AtLee <chris at atlee.ca> wrote:
> On Fri, Jul 22, 2011 at 1:49 PM, Joel Rosdahl <joel at rosdahl.net> wrote:
>> Justin Lebar's point that the cwd probably needs to be hashed seems
>> valid. Other than that, I think it looks generally fine, but I only have
>> limited knowledge about the -fprofile-* options so I can't say I
>> understand their interaction completely. Some comments and questions,
>> though:
>>
>> I think that the "output_to_real_object_first mode" should really be the
>> default and only mode. That would of course mean that the things in
>> from_cache() that need to be done after storing an object in the cache
>> should be refactored out somehow, but we can do that later.
>
> Sounds good. I'll need to add another flag to indicate that we need to
> hash cwd then if output_to_real_object_first is the default.
>
>> What about the -fprofile-generate=path and -fprofile-use=path forms?
>> Should those be detected as well?
>
> For -fprofile-generate, I don't think we need to worry about the
> profile directory since the inputs to the compilation aren't affected
> by where the profile data is stored. -fprofile-use does need to know
> where to look so that it can add the profile data to the hash. I'm
> half tempted to remove -fprofile-use support, I'm not sure how likely
> you are to get cache hits there. Running the same executable twice in
> a row generates different profile data.
>
>> tmp_obj is freed at the end of to_cache(), so output_obj will refer to
>> freed memory when dereferenced in from_cache() later. An x_strdup is needed.
>
> Fixed.
>
>> //-style comments won't compile on systems with C89 compilers, so use
>> /**/ instead.
>
> Fixed.
>
>> You should probably use hash_delimiter(hash, "-fprofile-use") or so
>> before hashing the gcda file (and then I guess that the hashing of "no
>> data" won't be necessary).
>
> Ah, that's what that function is for!
>
> Thanks for the feedback, I should have some new commits up shortly.
>
> Cheers,
> Chris