[PATCH] Generate a clang CompilationDatabase when running CMake.

[Justin Bogner via llvm-commits]

Justin Lebar <jlebar at google.com> writes:
>> We already document to do this on the command line in all of the tooling
>> docs
>
> FWIW that wasn't where I looked as someone new to the project; it
> doesn't show up in http://llvm.org/docs/GettingStarted.html.  Of
> course that page can't be a guide to all conceivable options.
>
>> does it actually make sense to default this to on?
>
> My thought was, one less thing you have to remember to do.  It's
> annoying enough that you have to add a .ycm_extra_config.
>
> In fact, while I have your attention...do you have any thoughts on how
> we might make adding a .ycm_extra_config file easier?  We could check
> one in to llvm/utils with instructions to copy it down to the root
> directory.  The problem with just sticking it in the root dir is that
> this file needs to specify where your object files are located.

Sorry, I don't use YCM so I'm not really familiar with the problem.

> That seems better than asking people to cargo-cult from the canonical
> .ycm_extra_config, which requires some minor but nontrivial
> modifications to work with llvm.
>
>> I suppose as long as this is fast to do (I haven't checked, is it?)
>> there's no harm in it.
>
> Doesn't appear to be significant.  On my macbook pro, after warming up
> the disk cache, I ran
>
> $ time cmake -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo ..
>
> Without the patch (ran 3 times):
>
> real 0m17.875s
> user 0m10.563s
> sys 0m5.935s
>
> real 0m18.335s
> user 0m10.948s
> sys 0m5.981s
>
> real 0m17.757s
> user 0m10.562s
> sys 0m5.836s
>
> With the patch:
>
> real 0m18.461s
> user 0m10.737s
> sys 0m6.215s
>
> real 0m18.243s
> user 0m10.805s
> sys 0m6.022s
>
> real 0m17.724s
> user 0m10.715s
> sys 0m6.009s

Fair enough. This LGTM.

> On Mon, Dec 14, 2015 at 10:53 AM, Justin Bogner <mail at justinbogner.com> wrote:
>> Justin Lebar via llvm-commits <llvm-commits at lists.llvm.org> writes:
>>> This generates a compile_commands.json file, which tells tools like
>>> YouCompleteMe and clang_complete exactly how to build each source file.
>>> ---
>>>  CMakeLists.txt | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>> diff --git a/CMakeLists.txt b/CMakeLists.txt
>>> index fc46413..208c0a8 100644
>>> --- a/CMakeLists.txt
>>> +++ b/CMakeLists.txt
>>> @@ -86,6 +86,10 @@ set(CMAKE_MODULE_PATH
>>>    "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
>>>    )
>>>
>>> +# Generate a CompilationDatabase (compile_commands.json file) for our build,
>>> +# for use by clang_complete, YouCompleteMe, etc.
>>> +set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
>>
>> We already document to do this on the command line in all of the tooling
>> docs, does it actually make sense to default this to on? I suppose as
>> long as this is fast to do (I haven't checked, is it?) there's no harm
>> in it.
>>
>>> +
>>>  option(LLVM_INSTALL_UTILS "Include utility binaries in the
>>> 'install' target." OFF)
>>>
>>>  option(LLVM_INSTALL_TOOLCHAIN_ONLY "Only include toolchain files
>>> in the 'install' target." OFF)
>>> _______________________________________________
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