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https://issues.apache.org/jira/browse/MESOS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alex Clemmer updated MESOS-3107:
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Component/s: (was: build)
cmake
> Define CMake style guide
> ------------------------
>
> Key: MESOS-3107
> URL: https://issues.apache.org/jira/browse/MESOS-3107
> Project: Mesos
> Issue Type: Task
> Components: cmake
> Reporter: Alex Clemmer
> Assignee: Alex Clemmer
> Labels: build, cmake
>
> The short story is that it is important to be principled about how the CMake
> build system is maintained, because there CMake language makes it difficult
> to statically verify that a configuration is correct. It is not unique in
> this regard, but (make is arguably even worse) but it is something that's
> important to make sure we get right.
> The longer story is, CMake's language is dynamically scoped and often has
> somewhat odd defaults for variable values (_e.g._, IIRC, target names passed
> to ExternalProject_Add default to "PREFIX" instead of erroring out). This
> means that it is rare to get a configuration-time error (_i.e._, CMake
> usually doesn't say something like "hey this variable isn't defined"), and in
> large projects, this can make it very difficult to know where definitions
> come from, or whether it's important that one config routine runs before
> another. Dynamic scoping also makes it particularly easy to write spaghetti
> code, which is clearly undesirable for something as important as a build
> system.
> Thus, it is particularly important that we lay down our expectations for how
> the CMake system is to be structured. This might include:
> * Function naming (_e.g._, making it easy to tell whether a function was
> defined by us, and where it was defined; so we might say that we want our
> functions to have an underscore to start, and start with the package the come
> from, like libprocess, so that we know where to look for the definition.)
> * What assertions we want to check variable values against, so that we can
> replace subtle errors (_e.g._, a library is accidentally named something
> silly like "PREFIX.0.0.1") with an obvious ones (_e.g._, "You have failed to
> define your target name, so CMake has defaulted to 'PREFIX'; please check
> your configuration routines")
> * Decisions of what goes where. (_e.g._, the most complex parts of the CMake
> MVPs is in the configuration routines, like `MesosConfigure.cmake`; to curb
> this, we should have strict rules about what goes in that file vs other
> files, and how we know what is to be run before what. Part of this should
> probably be prominent comments explaining the structure of the project, so
> that people aren't confused!)
> * And so on.
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