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bug#6617: linux kernel C style (fwd)

From: Dimitrios Apostolou
Subject: bug#6617: linux kernel C style (fwd)
Date: Tue, 13 Jul 2010 12:17:38 +0300 (EEST)
User-agent: Alpine 2.00 (LNX 1167 2008-08-23)

On Tue, 13 Jul 2010, Dan Nicolaescu wrote:
Dimitrios Apostolou <address@hidden> writes:

Hi, I sent the following to help-gnu-emacs and got no reply, maybe
this list is more relevant.

---------- Forwarded message ----------
Date: Thu, 8 Jul 2010 21:56:09 +0300 (EEST)
From: Dimitrios Apostolou <address@hidden>
To: address@hidden
Subject: linux kernel C style

Hello list,

is the "linux" c-style supposed to be compliant to the linux kernel
style guidelines? I just realised that all this time emacs was
indenting my code slightly wrong, specifically the use of spaces is
forbidden, even when continuing the argument list of a function.

Is that really the case?  Is this requirement documented anywhere?

In the file Documentation/CodingStyle search for "emacs". Warning: the language is a bit toxic for emacs devs/users.

There is also another point which is not clear but says the following:

Statements longer than 80 columns will be broken into sensible chunks. Descendants are always substantially shorter than the parent and are placed substantially to the right. The same applies to function headers with a long argument list. Long strings are as well broken into shorter strings. The only exception to this is where exceeding 80 columns significantly increases readability and does not hide information.

It is then followed by an example which is is indented only with tabs.

Looking at a random file in the linux- kernel: kernel/sched.c one can see:

static void update_group_shares_cpu(struct task_group *tg, int cpu,
                                    unsigned long sd_shares,
                                    unsigned long sd_rq_weight,
                                    unsigned long *usd_rq_weight)

The arguments starting from sd_shares are indented using a few tabs
followed by a few spaces.
The above is not the only occurrence, there are many others in the same file.

My guess is that those are inconsistencies caused by the current "linux" style in emacs, but perhaps this should be posted to LKML to verify.

Another point: to enforce the use of the correct style, a file called
.dir-locals.el should be placed at the top level of the kernel tree
with the following [completely untested] contents:

((c-mode . ((c-file-style . "linux")
           (tab-width . 8)
           (indent-tabs-mode . t))))

With this users of emacs-23+ will get the correct settings for editing
the kernel by default.


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