[TUHS] : C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 8:43 AM Alejandro Colomar
<alx.manpages at gmail.com> wrote:
> On 3/13/23 13:19, Dan Cross wrote:
> > On Mon, Mar 13, 2023 at 6:41 AM Alejandro Colomar (man-pages)
> > <alx.manpages at gmail.com> wrote:
> >> Or you can ask GCC to respect your view of the language with things like -fno-strict-aliasing, -fwrapv, and -fno-trapv.
> >
> > The problem that is that you are then no longer programming in "C",
> > but rather some dialect of "C" that happens to share the same syntax,
> > but with different semantics. That may be fine, or it may not, but it
> > can lead to all sorts of footgun traps if one is not careful.
>
> Well, it depends on what you call "C".  There are many dialects,
> and I'm not sure there's any which I'd call "C".

That's precisely the problem. :-)

        - Dan C.


> The 3 main dialects are "ISO C", "GNU C", and "K&R C".  And then
> there are subdialects of them.  We could say "C" is "ISO C", since,
> well, it's _the_ standard.  But then, ISO C shares the aliasing
> issues that GNU C has, so by avoiding the GNU C compiler you're
> not avoiding the issues we're talking about; moving to a compiler
> that only talks ISO C is going to keep the issues.  You'll need
> a compiler that talks K&R C, or some other dialect that doesn't
> have aliasing issues.
>
> At that point, since you already need a subdialect of C, GCC is
> one such compiler, since it provides a comprehensive set of flags
> to tune your dialect.
>
> Or you could move to a compiler that talks its own dialect
> (probably some subdialect of K&R C, as I expect Plan9 C is, but
> I never tried it).  But that's not much different from asking
> such dialect to GCC.
>
> Cheers,
>
> Alex
>
> >
> >         - Dan C.