[cfe-dev] Where should tooling logic live? I have no idea...

Douglas Gregor dgregor at apple.com
Fri Jun 29 14:35:51 PDT 2012

On Jun 29, 2012, at 12:52 PM, Chandler Carruth <chandlerc at google.com> wrote:

> I have a specific question about one of your points that is much more meta than the original thread:
> On Fri, Jun 29, 2012 at 9:09 AM, Douglas Gregor <dgregor at apple.com> wrote:
>        - It should live in a separate repository of Clang tools alongside (but not a part of) the main Clang repository.
> I think it's clear we will need some side repository that is home of contributed tools that are maintained and released along with Clang, but not necessarily of interest to everyone.
> What isn't clear to me is how we should decide when a tool belongs there or should actually come along with the core Clang checkout. My initial guess at where this tool should live was actually in the core Clang repository, so I suspect you have a different set of heuristics you're using. Could you elaborate on them?
> Some observations that have motivated my initial guesses:
> 1) It seems like 'clang-check' and maybe 'clang-fixit' (which should be the Tooling analog to clang -fixit-always) are really good tools to put directly in the Clang tree
> 2) It seems like ad-hoc tools like the one which removes redundant calls to std::string::c_str() should not be in the main Clang tree.
> 3) I suspect that truly generic refactoring tools (let's say for example, a 'rename' tool) could very reasonably go either direction.
> 3.1) I suspect that this will be motivated by the fact that the generic refactoring logic will be structured as a library, shared by lots of tools
> 4) The idea of a Clang service layer complicates this -- in that model *all* of the tools should be libraries bundled into the server.
> Combining those observations leaves me with no clear feeling for where things should live.

I see the main Clang repository as being responsible for:

	1) The compiler proper
	2) IDE integration
	3) Clang service layer (when it happens)
	4) Infrastructure to build Clang-based tools and plugins
	5) Testing infrastructure for all of the above

To me, that's the core of what Clang *is*. Things like the static analyzer, ObjC rewriter, ARC migrator, c_str() pruner, C++11 migrator, etc. are outside of that core and should eventually live in the side repository.

I worry a little bit about the side repository becoming broken. Obviously, there's an additional testing burden to consider here, and I do worry (in the abstract) that we'll be making trouble for ourselves by having to maintain a pile of standalone tools outside of the main repository. But, I think we can handle this.

The Clang service layer does complicate this. Allowing the server to load plugins would solve the issue for plugins that ride on the normal compile jobs. Perhaps we can make it not completely painful to turn a standalone tool into a plugin that can be loaded by the server.

	- Doug
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