Re: [edk2-CCodingStandardsSpecification PATCH 1/2] Source Files / General Rules: limit line lengths to 80 columns

[Jordan Justen <jordan.l.justen@intel.com>]

On 2017-08-11 15:52:44, Ard Biesheuvel wrote:
> On 11 August 2017 at 17:48, Laszlo Ersek <lersek@redhat.com> wrote:
> > We currently say "stick with 80 if it's convenient, extend to 120
> > otherwise".
> 
> It doesn't say that. It says you can make an exception for postfix
> comments, which is not unreasonable imo.
> 
> This means most of the code in MdePkg/MdeModulePkg (afaik) already
> violates the old coding styile, so what good is it going to do to
> further restrict it?

True, but I'm not sure it is widely known that the rule only applies
to postfix comments.

I guess we could add checking into 'PatchCheck.py' for line length,
and I guess it could handle the postfix exception as well. We might
also need to be more consistent with using PatchCheck.py... :)

The current 'rule' only carves out an exception for postfix comments,
and I guess I prefer to drop that. I'd rather see such (somewhat rare)
comments moved up if they are necessary.

Regarding violations, I decided to try to check this rule, and you are
correct in that it is often violated.

To find lines longer than 80 columns, I used:

$ git grep -P -e '^(?!\s{0,16}//)' --and \
              -e '^.{80}\s*[^\s]' --and \
              --not -e 'licen|accomp' -- *.c *.h | wc -l

'^(?!\s{0,16}//)': Skip non-postfix comment lines
'^.{80}\s*[^\s]': Lines with a non-space after 80 chars
'licen|accomp': avoid BSD license lines that are long

To find lines with postfix comments, I added:

'.*[^/].*//'

For MdePkg:
22244 long lines, and only 1522 long lines with a postfix comment.

For MdeModulePkg:
33248 long lines, and only 720 long lines with a postfix comment.

For OvmfPkg:
1116 long lines, and only 64 long lines with a postfix comment.

How about lines > 120 in length?

$ git grep -P '^.{120}\s*[^\s]' -- *.c *.h |wc -l

MdeModulePkg: 2017
MdePkg: 521
OvmfPkg: 45

-Jordan

> 
> > This is too lax; much new edk2 code ignores the 80 columns
> > recommendation, resulting in source files that are hard to read for some
> > contributors. Remove the 120 columns excuse and make 80 columns a
> > requirement.
> >
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: Jordan Justen <jordan.l.justen@intel.com>
> > Cc: Leif Lindholm <leif.lindholm@linaro.org>
> > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> > ---
> >  5_source_files/README.md | 17 ++++++++++++-----
> >  README.md                |  1 +
> >  2 files changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/5_source_files/README.md b/5_source_files/README.md
> > index a93492db4f0f..546d44d94fcb 100644
> > --- a/5_source_files/README.md
> > +++ b/5_source_files/README.md
> > @@ -33,12 +33,19 @@
> >
> >  ## 5.1 General Rules
> >
> > -### 5.1.1 Lines shall be 120 columns, or less
> > +### 5.1.1 Lines shall be 80 columns, or less
> >
> > -Preferably, limit line lengths to 80 columns or less. When this doesn't leave
> > -sufficient space for a good postfix style comment, extend the line to a total
> > -of 120 columns. Having some level of uniformity in the expected width of the
> > -source is useful for viewing and printing the code.
> > +Limit line lengths to 80 columns.
> > +
> > +Lines longer than 80 columns make it more difficult for the reader to find the
> > +beginning of the next line. They also tend to prevent users from displaying two
> > +source listings side-by-side on common display devices.
> > +
> > +When the 80 columns limit doesn't leave sufficient space for a postfix style
> > +comment, break the line into shorter segments at logical boundaries (for
> > +example, between the arguments of a function call, adhering to the spacing
> > +rules), or replace the postfix style comment with a standalone comment that
> > +precedes the statement.
> >
> >  ### 5.1.2 Do not use tab characters
> >
> > diff --git a/README.md b/README.md
> > index 8b9675b94937..8fad5a327b8c 100644
> > --- a/README.md
> > +++ b/README.md
> > @@ -112,3 +112,4 @@ Copyright (c) 2006-2017, Intel Corporation. All rights reserved.
> >  | 2.1      | DRAFT for REFORMAT                                                                                                                                | 10/30/2015 |
> >  | 2.2      | Convert to Gitbook                                                                                                                                | June 2017  |
> >  |          | [#425](https://bugzilla.tianocore.org/show_bug.cgi?id=425) [CCS] clarify line breaking and indentation requirements for multi-line function calls |            |
> > +|          | Limit lines to 80 columns                                                                                                                         |            |
> > --
> > 2.13.1.3.g8be5a757fa67
> >
> >