Hard-to-understand line in xfaces.c

Hard-to-understand line in xfaces.c

[Stefan Kangas]

Could someone explain this line in xfaces.c:7184?

    len -= 0 < len && name[len - 1] == '\n';

It seems rather mysterious to me; for example, does it actually do
anything?

Re: Hard-to-understand line in xfaces.c

[Andrea Corallo]

Stefan Kangas <stefankangas@gmail.com> writes:

> Could someone explain this line in xfaces.c:7184?
>
>     len -= 0 < len && name[len - 1] == '\n';
>
> It seems rather mysterious to me; for example, does it actually do
> anything?

If len is greater than zero and name[len - 1] is '\n' then is decreasing
len by one.  Only form the line I don't have the context of why is doing
that.

  Andrea

Re: Hard-to-understand line in xfaces.c

[Eli Zaretskii]

> From: Andrea Corallo <acorallo@gnu.org>
> Cc: emacs-devel@gnu.org
> Date: Mon, 22 Jul 2024 10:35:18 -0400
> 
> Stefan Kangas <stefankangas@gmail.com> writes:
> 
> > Could someone explain this line in xfaces.c:7184?
> >
> >     len -= 0 < len && name[len - 1] == '\n';
> >
> > It seems rather mysterious to me; for example, does it actually do
> > anything?
> 
> If len is greater than zero and name[len - 1] is '\n' then is decreasing
> len by one.  Only form the line I don't have the context of why is doing
> that.

It wants to exclude the newline from the name of the color (which is
the last field on each line).

Re: Hard-to-understand line in xfaces.c

[Stefan Kangas]

Andrea Corallo <acorallo@gnu.org> writes:

> Stefan Kangas <stefankangas@gmail.com> writes:
>
>> Could someone explain this line in xfaces.c:7184?
>>
>>     len -= 0 < len && name[len - 1] == '\n';
>>
>> It seems rather mysterious to me; for example, does it actually do
>> anything?
>
> If len is greater than zero and name[len - 1] is '\n' then is decreasing
> len by one.

Doh!  Thanks for clearing it up for me.

Re: Hard-to-understand line in xfaces.c

[Pip Cet]

On Monday, July 22nd, 2024 at 14:20, Stefan Kangas <stefankangas@gmail.com> wrote:
> Could someone explain this line in xfaces.c:7184?
> 
> len -= 0 < len && name[len - 1] == '\n';
> 
> It seems rather mysterious to me; for example, does it actually do
> anything?

I'd rewrite it as

if (len > 0 && name[len - 1] == '\n')
  len--;

though I'd test it actually does the same thing first :-)

Pip