Re: [PATCH] Cleanup include/net/tcp.h include-files and coding-style

On Sun, 2011-01-09 at 22:32 +0100, Christoph Paasch wrote:

Hello,

On Sunday, January 09, 2011 wrote Randy Dunlap:

quoted

On Sun,  9 Jan 2011 21:55:34 +0100 Christoph Paasch wrote:
If there is something in net/tcp.h that uses data or functions from
<linux/list.h>, then <linux/list.h> should be #included in net/tcp.h,
whether some other file pulls it in indirectly or not.

etc. etc. etc.

Why?

IMHO I think that it increases compile-time.
Ok, here in that case it only increases it slightly (probably it isn't even 
measurable).

The cost of repeated inclusion is minimal.  GCC's preprocessor
recognises when the entire content of a file is conditional on #ifndef
FOO and will not even open it again if FOO is defined.

 But, if *all* the files would be more strict in including, I'm 
sure that it would make a difference.
The less files you include, the faster the compilation will be.

In net/tcp.h there were even 4 unnecessary included files.

And, then we would also need to include:
net/net_namespace.h (for struct net)

Also, I think that it makes the code more readable and also easier to 
maintain. The more files we include, the bigger the chance is that we will end 
up with plenty of files unnecessarily included, and thus the compile-time will 
explode.

If a file directly references definitions that are supposed to be
provided by a certain header, changing it to rely on indirect inclusion
of that header generally does *not* aid maintenance.

(There are some cases where you should rely on indirect inclusion, such
as where <linux/foo.h> includes <asm/foo.h>.)

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
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