[cmake-developers] How to handle dependencies of protobuf files ?

[Eric Noulard]

Le mer. 30 mai 2018 à 15:12, Brad King <brad.king at kitware.com> a écrit :

> On 05/29/2018 04:00 PM, Alexander Neundorf wrote:
> >> In order to handle implicit dependencies like that implied by
> >>
> >>     import "MyBase.proto";
> >>
> >> then they would somehow need to be extracted from source content.
> >
> > Would that have to be implemented similar to the C dependency scanning ?
>
> Yes, but even better would be if we can ask protoc to print the
> dependencies
> out for us so we don't have to parse the sources ourselves.
>

protoc can already do something like that but it spits out a makefile
includable file.

see --dependency_out=FILE option.
Write a dependency output file in the format
                              expected by make. This writes the transitive
                              set of input file paths to FILE

moreover the generated makefile depends on the langage generator used
(--cpp_out, --java_out, --python_out, ...) because dependencies are
expressed between proto and
generated source files.

May be it would be possible to write a protoc "plugin"
https://www.expobrain.net/2015/09/13/create-a-plugin-for-google-protocol-buffer/

which would spit out easy to digest dep spec for CMake.

Unfortunately I'm not volunteering :-( just giving some idea.


> > so the cheap solution would be to add an argument to
> PROTOBUF_GENERATE_CPP()
> > to list proto-files these proto-files depend on
>
> Yes, that would be a good intermediate solution.
>
> -Brad
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-- 
Eric
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