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Re: [RFC] Characters per line: from punch card (80) to line printer (132) (was: [Patch][OpenMP/OpenACC/Fortran] Fix mapping of optional (present|absent) arguments)


On Thu, Dec 05, 2019 at 08:56:35PM +0000, Jonathan Wakely wrote:
> On Thu, 5 Dec 2019 at 20:07, Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> > On Thu, Dec 05, 2019 at 05:03:43PM +0000, Jonathan Wakely wrote:
> > > C++17 introduces a nice feature, with rationale similar to declaring
> > > variables in a for-loop init-statement:

> > > Unfortunately nearly every time I've tried to use this recently, I've
> > > found it's impossible in 80 columns, e.g. this from yesterday:
> > >
> > >     if (auto __c = __builtin_memcmp(&*__first1, &*__first2, __len) <=>
> > > 0; __c != 0)
> > >       return __c;
> > >
> > > When you're forced to uglify every variable with a leading __ you run
> > > out of characters pretty damn quickly.
> >
> > If using this "nice feature" forces you to uglify your code, then maybe
> > it is not such a nice feature, and you should not use it.
> 
> The uglification has absolutely nothing to do with the 'if'
> init-statement feature, all code in libstdc++ headers has to be
> uglified, always. Blame the C preprocessor for that, not C++ features.
> 
> My point is that 80 characters runs out quicker when 10% of it goes on
> visual noise that's only needed because the C preprocessor means we
> can't have nice names.

(Not sure where the preprocessor comes in, these underscores are just to
satisfy language rules afaics, but maybe you mean something else?)

Or you could write

    auto __c = (__builtin_memcmp(&*__first1, &*__first2, __len) <=> 0);
    if (__c)
      return __c;

which is much easier to read, to my eyes anyway.  And it is exactly the
same for the compiler.

Wrapping everything inside-out just for the artificial goal of having
things defined in slightly tighter scopes feels futile.


Segher


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