[CMake] Generate sources

[Layus]

On 16/12/15 17:53, Mark Stijnman wrote:
> On Wed, Dec 16, 2015 at 2:29 PM, Layus <layus.on at gmail.com 
> <mailto:layus.on at gmail.com>> wrote:
>
>     Hi,
>
>     I am looking for a way to share an archive of a partially compiled
>     project to speedup compilation time and configuration hassle for
>     the users.
>
>     I have a project that works in two steps.
>     First a source generator is built (based on clang) and generates
>     some extra source files based on the existing source files.
>     Then the normal compilation process takes places, building the
>     application from both original and generated sources.
>
> <snip>
>
>     Now, is it possible to distribute a source archive with the
>     generated sources, in such a way that any user unpacking the
>     archive and running cmake would not have to generate the extra
>     sources ?
>
>     This would be useful because
>     i) the project is tricky to configure and
>     ii) the generated sources are not dependent on the user config, so
>     building the generator is just useless computation time on the user.
>
>     The ideal scheme would be something like
>
>         [developper]
>         $ cmake -DCLANG=config
>         $ make generate
>         $ make package_source
>
>         [user]
>         $ unpack
>         $ cmake -DUSER=config
>         $ make # builds only the application, reusing the shipped
>     generated sources.
>         $ make install
>
>     ... but when the user runs cmake, he overwrites the generated
>     Makefiles and the extra sources are generated again.
>
>     Any idea ?
>
>     layus.
>
>     -- 
>
>
> I'd probably just make it such that the CMake script automatically 
> detects the presence of the generated files, and if they don't exist, 
> generate them. For example:
> 1. Set a variable GENERATED_FOLDER to 
> ${CMAKE_CURRENT_SOURCE_DIR}/generated
> 2. If ${GENERATED_FOLDER} doesn't exist, set it to 
> ${CMAKE_CURRENT_BINARY_DIR}/generated instead, and set up the targets 
> that will generate the files in that folder.
> 3. Simply use the ${GENERATED_FOLDER} variable to add the generated 
> files to your application.
> 4. Set up the package_source target so that it packages the files from 
> ${GENERATED_FOLDER} to a folder called "generated" (such that if a 
> user unpacks from there, they will end up in 
> ${CMAKE_CURRENT_SOURCE_DIR}/generated), and you're done.
> 5. Recommended: add a check for the existence of target "generate", 
> and if so, set it as a dependency for your application and package_source.
>
> This way, you don't need to remember what switches to use, or when to 
> use "make generate". If you need to make it possible for a user to 
> force generation, you can alter step 2 to also run when a command line 
> option is supplied.
>
> Hope that helps,
>
> Best regards Mark

Works like a charm.

(See https://github.com/layus/mozart2/tree/cache_generated_code)

Thanks !

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