On Sun, Oct 3, 2021 at 7:19 AM Utkarsh Verma <utkarshverma294@xxxxxxxxx> wrote:
>
> On Sun, Oct 03, 2021 at 10:08:17AM +0530, Dwaipayan Ray wrote:
> > On Sat, Oct 2, 2021 at 8:15 PM Utkarsh Verma <utkarshverma294@xxxxxxxxx> wrote:
> > >
> > > Added and documented UNNECESSARY_ELSE message type.
> > >
> > > Signed-off-by: Utkarsh Verma <utkarshverma294@xxxxxxxxx>
> > > ---
> > > Changes in v2:
> > > - Included the continue statement.
> > >
> > > Documentation/dev-tools/checkpatch.rst | 77 ++++++++++++++++++++++++++
> > > 1 file changed, 77 insertions(+)
> > >
> > > diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> > > index f0956e9ea2d8..b7c41e876d1d 100644
> > > --- a/Documentation/dev-tools/checkpatch.rst
> > > +++ b/Documentation/dev-tools/checkpatch.rst
> > > @@ -1166,3 +1166,80 @@ Others
> > >
> > > **TYPO_SPELLING**
> > > Some words may have been misspelled. Consider reviewing them.
> > > +
> > > + **UNNECESSARY_ELSE**
> > > + Using an else statement just after a return/break/continue statement is
> > > + unnecessary. For example::
> > > +
> > > + for (i = 0; i < 100; i++) {
> > > + int foo = bar();
> > > + if (foo < 1)
> > > + break;
> > > + else
> > > + usleep(1);
> > > + }
> > > +
> > > + is generally better written as::
> > > +
> > > + for (i = 0; i < 100; i++) {
> > > + int foo = bar();
> > > + if (foo < 1)
> > > + break;
> > > + usleep(1);
> > > + }
> > > +
> > > + It helps to reduce the indentation and removes the unnecessary else
> > > + statement. But note, there can be some false positives because of the
> > > + way it is implemented in the checkpatch script. The checkpatch script
> > > + throws this warning message if it finds an else statement and the line
> > > + above it is a break/continue/return statement indented at one tab more
> > > + than the else statement. So there can be some false positives like::
> > > +
> > > + int n = 15;
> > > + if (n > 10)
> > > + n--;
> > > + else if (n == 10)
> > > + return 0;
> > > + else
> > > + n++;
> > > +
> > > + Now the checkpatch will give a warning for the use of else after return
> > > + statement. If the else statement is removed then::
> > > +
> > > + int n = 15;
> > > + if (n > 10)
> > > + n--;
> > > + else if (n == 10)
> > > + return 0;
> > > + n++;
> > > +
> > > + Now both the n-- and n++ statements will be executed which is different
> > > + from the logic in the first case. As the if block doesn't have a return
> > > + statement, so removing the else statement is wrong.
> > > +
> > > + Always check the previous if/else if blocks, for break/continue/return
> > > + statements, and do not blindly follow the checkpatch advice. One
> > > + patch (https://lore.kernel.org/all/20200615155131.GA4563@sevic69/)
> > > + even made it to the mainline, which was again reverted and fixed.
> > > + Commit 98fe05e21a6e ("staging: rtl8712: Remove unnecesary else
> >
> > s/unnecesary/unnecessary
>
> It is a spelling mistake in the commit message itself, and I have quoted
> that message, so I didn't change the message.
>
> > > + after return statement.")
I wonder if this detailed description of the example belongs here; and
we summarize it as:
Do not blindly follow checkpatch's advice here, as blind changes due
to this rule have already caused some disturbance, see commit ....
> > > +
> > > + Also, do not change the code if there is only a single return statement
> > > + inside if-else block, like::
> > > +
> > > + if (a > b)
> > > + return a;
> > > + else
> > > + return b;
> > > +
> > > + now if the else statement is removed::
> > > +
> > > + if (a > b)
> > > + return a;
> > > + return b;
> > > +
> > > + there is no considerable increase in the readability and one can argue
> > > + that the first form is more readable because of the indentation. So
> > > + do not remove the else statement in case of a single return statement
> > > + inside the if-else block.
> > > + See: https://lore.kernel.org/lkml/20140925032215.GK7996@xxxxxxxxxxxxxxxxxx/
> > > --
> > > 2.25.1
> > >
> >
> > I think this message is unnecessarily long for a warning that's understandable
> > at best without the verbose part. Try to shorten it up with only what's
> > required for a user to understand why the warning is there.
> >
>
> Okay, I will try writing it more precisely as Lukas said.
>
> > Dwaipayan.
