Re: Coding Style: Reverse XMAS tree declarations ?

On 04.11.2016 18:44, Joe Perches wrote:

On Fri, 2016-11-04 at 11:07 -0400, David Miller wrote:

quoted

From: Lino Sanfilippo <redacted>

quoted

On 04.11.2016 07:53, Joe Perches wrote:

quoted

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to
shortest
#446: FILE: drivers/net/ethernet/ethoc.c:446:
+                    int size = bd.stat >> 16;
+                    struct sk_buff *skb;

should not this case be valid? Optically the longer line is already
before the shorter.
I think that the whole point in using this reverse xmas tree ordering
is to have
the code optically tidied up and not to enforce ordering between
variable name lengths.

That's correct.

And also another reason the whole reverse xmas tree
automatic declaration layout concept is IMO dubious.

Basically, you're looking not at the initial ordering
of automatics as important, but helping find a specific
automatic when reversing from reading code is not always
correct.

Something like:

static void function{args,...)
{
	[longish list of reverse xmas tree identifiers...]
	struct foo *bar = longish_function(args, ...);
	struct foobarbaz *qux;
	[more identifers]

	[multiple screenfuls of code later...)

	new_function(..., bar, ...);

	[more code...]
}

and the reverse xmas tree helpfulness of looking up the
type of bar is neither obvious nor easy.

In this case it is IMHO rather the declaration + initialization that makes
"bar" hard to find at one glance, not the use of RXT. You could do something like

 	[longish list of reverse xmas tree identifiers...]
 	struct foobarbaz *qux;
 	struct foo *bar;

 	bar = longish_function(args, ...);

to increase readability. 

Personally I find it more readable to always use a separate line for initializations
by means of functions (regardless of whether the RXT scheme is used or not). 
 

My preference would be for a bar that serves coffee and alcohol.

At least a bar like this should not be too hard to find :)

Regards,
Lino