Re: [RFC] duplicate #include check for build system

From: Daniel Barkalow
Date: Tue Feb 21 2006 - 02:33:11 EST


On Tue, 21 Feb 2006, Herbert Poetzl wrote:

> Hi Sam! Folks!
>
> recently had the idea to utilize cpp or sparse to
> do some automated #include checking, and I came up
> with the following proof of concept:
>
> I just replaced the sparse binary by the following
> script (basically hijacking the make C=1 system)
>
> it would allow kernel developers to easily identify
> duplicate includes, which in turn, might reduce
> dependancies and thus build time ...

I think the kernel style is to encourage duplicate includes, rather than
removing them. Removing duplicate includes won't remove any dependancies
(since the includes that they duplicate will remain). And it makes it
harder to remove unnecessary includes (which does reduce dependancies),
because when header A stops needing header B, various other code could
expect that including header A means they get header B, and these places
have to be found and the formerly-duplicate include put back. So you
actually do best to have lots of duplicate includes and aggressively prune
unnecessary includes.

-Daniel
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