Re: [PATCH] Fix line too long warning

[Joe Perches <joe@perches.com>]

On Sun, 2017-10-29 at 18:54 +0300, Yury Norov wrote:
> At second, and most important, refer Documentation/process/coding-style.rst:
> Now, some people will claim that having 8-character indentations makes
> the code move too far to the right, and makes it hard to read on a 
> 80-character terminal screen.  The answer to that is that if you need 
> more than 3 levels of indentation, you're screwed anyway, and should fix
> your program.
> 
> The real problem here is not "line too long", but "indentation level too
> big" - 5. And it worth to address real problem.

Line length issues can be a combination of several factors:

o identifier length
o quantity of dereferences
o indentation depth
o code complexity

4 indentation depth levels are not a real issue.
A significant percentage of lines in the kernel
are 4 or more tab indent levels deep.

checkpatch suggests that 6 or more is the depth level
that should cause real concern.

Here's a little breakdown of lines that start with
a tab followed by a c90 keyword in the kernel

$ git grep -P "^\t+(if|for|do|while|\}|else|switch|return|case|break|continue|goto)\b" -- "*.[ch]" | \
  cut -f2- -d":" | perl -p -e 's/(^\t+).*/\1/' | \
  sort | uniq -c | sort -rn | \
  awk '{total += $1; count[i++] = $1} END { for (j = 0; j < i; j++) { printf "%d\t%d\t%.2f%%\n", j + 1, count[j], count[j] / total * 100 }}'
1	1325462	52.19%
2	863007	33.98%
3	271844	10.70%
4	64009	2.52%
5	12502	0.49%
6	2199	0.09%
7	501	0.02%
8	166	0.01%
9	51	0.00%
10	20	0.00%
11	10	0.00%
12	4	0.00%
13	1	0.00%

I think it could reasonably be argued that the
indentation depth warning (DEEP_INDENTATION)
should start at 5 and not at 6.

---
 scripts/checkpatch.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 6bdd43d5dec5..923e4ff09d24 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3353,7 +3353,7 @@ sub process {
 
 			my ($level, @ctx) = ctx_statement_level($linenr, $realcnt, 0);
 
-			if ($line =~ /^\+\t{6,}/) {
+			if ($line =~ /^\+\t{5,}/) {
 				WARN("DEEP_INDENTATION",
 				     "Too many leading tabs - consider code refactoring\n" . $herecurr);
 			}