[dpdk-dev] [PATCH] doc: coding style: use linux kernel style for indentation

Bruce Richardson bruce.richardson at intel.com
Wed Jan 13 16:07:08 CET 2016

On Wed, Jan 13, 2016 at 03:58:49PM +0800, Yuanhan Liu wrote:
> Using two tabs for "if" (or "while") statements is a bit weird to me.
> Also, using one tab unconditionaly for function definitions and
> prototypes doesn't look great.
> Here I'd suggest to use the indentation style the Linux kernel
> project prefers: to align with the open brace with tabs and
> additonal spaces (when necessary).
> Example:
>   static int
>   rte_eal_foo_bar(int a_long_argument_1, int another_long_argument_2,
>                   struct foo *yet_another_long_argument_3)
>   ret = rte_eal_foo_bar(a_long_argument_1, another_long_argument_2,
>                         yet_another_long_argument_3);
>   if (really_long_variable_name_1 == really_long_variable_name_2 &&
>       var3 == var4) {
>           x = y + z;
>           ....;
>   }
> Cc: Thomas Monjalon <thomas.monjalon at 6wind.com>
> Cc: Siobhan Butler <siobhan.a.butler at intel.com>
> Cc: John McNamara <john.mcnamara at intel.com>
> Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
> ---

While it's not a big deal - yet is something likely to trigger massive discussion
my objections to this style of indentation is two-fold:

1. It means that we are using a mix of tabs and spaces for indentation at the 
start of a line. I think it's more consistent that all whitespace at the start
of a line should be either tabs or spaces, but not a mixture.
2. It makes how the code look much more dependent upon the tab-size being used
in the viewer - being able to adjust how much whitespace is seem at the start of
each line is a major advantage of using tabs rather than spaces for indentation.
For anyone using a 4-character tabstop - probably the most popular tabstop value
after an 8-char one - aligning an if-statement continuation to the opening brace
will cause it to align with the body of the block.

So, while the two-tab indent may look "a bit weird" it does solve the two issues
above. I believe practical benefits should override initial impressions. [It took
me a while to get used to also, but now I very much like it as a style.]


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