[PATCH] Allow multiple modules with the same name to coexist in the module cache

[Argyrios Kyrtzidis]

On Mar 31, 2014, at 4:44 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> On Mon, Mar 31, 2014 at 4:23 PM, Argyrios Kyrtzidis <kyrtzidis at apple.com> wrote:
> >
> > What I'm suggesting is:
> >
> > 1) Drop the -I paths that are earlier than the module in the header search path when building the module
> > 2) Include the rest of the header search paths in the configuration hash for the module
> 
> This will prevent us from sharing system modules across projects, and, as Ben already mentioned, will result in an explosion of module files, even within the same project.
> 
> Why? System modules would only have system include paths, and these would usually be the same across projects, right?

I see what you mean, but we also need to support the case where the system framework developer can point to the framework in his local directory to be used, instead of the system one, how do you suggest we allow this ?

> 
> Even if we include the search paths in the module hash we will still need to re-lookup the module dependencies before loading the module, because a new module.map may have showed up somewhere in the search paths since the time we built the module; unless I’m missing something, I don’t see any benefit in including the header search paths in the hash.
> 
> The hash should include everything that affects the way the module is built. If we're transferring include paths from the user of the module to the module build, the hash should include those paths, or two modules with different search paths could collide in the cache.

The collision is avoided by using the path to the module.map as Ben proposes; if different search paths resolve to different module dependencies, this is a case where we need to rebuild, but the same is true if the same paths are used but a different module.map shows up as dependency.

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