NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/std/c/216

Internet Message Format | 1996-08-06 | 4.7 KB

Path: solon.com!not-for-mail
From: [e-mail] (Peter Seebach)
Newsgroups: comp.lang.c,comp.std.c
Subject: Re: Integral conversion e.t.c. (was: Re: Hungarian notation)
Date: 29 Jan 1996 09:00:10 -0600
Organization: Usenet Fact Police (Undercover)
Message-ID: <4eindq$[e-mail]>
References: <[e-mail]> <[e-mail]> <4edqh2$[e-mail]> <[e-mail]>
NNTP-Posting-Host: solutions.solon.com

In article <[e-mail]>,
James Kanze US/ESC 60/3/141 #40763 <[e-mail]> wrote:
>In article <4edqh2$[e-mail]> [e-mail]
>(Peter Seebach) writes:
>In the particular case which you cite, I do *not* believe that gcc
>will compile the program without a diagnostic if the program is in a
>file called a.c.  More ever, the compiler documentation definitly
>states that only programs in files whose names end in .c will be
>compiled as C.  (A legal restriction, as far as I can see.)

That's an interesting question; the standard does not visibly make any
such requirements, but you could argue that gcc is only a conforming compiler
when invoked on a file ending in .c.

Yes, it would *have* to give a diagnostic for a Fortran program; nonetheless,
the program is *still* conforming if it is accepted.  I think this is a
botch; the standard should probably distinguish between extensions and
violations.

>To tell the truth, I'm not sure what the answer is.  The text
>concerning main is in the chapter describing the environment.  It
>doesn't appear as a semantic restriction or anything.  It simply
>states that on start-up, a function called main will be called, and
>that the implementation must support the following forms.  It doesn't
>seem (to me, at least) to say anything about what other forms it might
>support, or what the implementation must do if given a fully other
>definition of main.

I would tend to expect a diagnostic in strict ANSI mode, and would also
expect a diagnostic for including <sys/stat.h> in strict ANSI mode.  Neither
is often forthcoming.

gcc warns only on implementations where they consider it a hosted environment;
on most systems, they weasel and claim to be a freestanding implementation.

>Normally, I would expect (at the very least) a compiler to generate a
>warning or an error for a main that it did not support.  In fact,
>however, my compiler (gcc) accepts the following definition without
>the slightest complaint, although I'd rather not think about what will
>happen when I access parameter d:

>    int main( char a , int b , long c , double d )

I think that may actually legitimately require a diagnostic; 5.1.2.2.1 gives
us a constraint (?) of "If they are defined, the parameters to the main
function shall obey the following constraints: ..." and some definitions.

I would take this as implying that main *must* conform.  I would like to see
them go from "can be declared" to "shall be declared".

Already, though, it is clear than any main other than those provided makes
undefined behavior.

>Yes and no.  In comp.std.c, the discussion is exactly about what is
>legal according to the standard.  In comp.lang.c (to which this
>article is also cross-posted), the discussion should generally be a
>bit more open.

It's debated.  Generally, questions about features of specific compilers or
OS's are off-topic, even when they relate to conforming programs.  Only
strictly conforming programs (or attempts at such, when people are asking
questions) are going to be usable and testable by the whole readership.
(I doubt you can find a single extension that works on *all* machines
we use.)

>Thus, for example, in comp.std.c, a program with a variable named far
>is illegal, and that is it.  In comp.lang.c (and I hope in its
>moderated variant), I would hope that someone would point out that,
>legal or not, it's going to get you into trouble.

(I assume you meant "...is legal, ...")

I generally allow some discussion of system arcana in clcm, but try to
keep it constrained to question s of portability.

It appears that the DOS world has started using __far, so I stopped worrying.
I declare variables with names like "near" or "far", and if a compiler can't
take it' the compiler is broken.

I have actually had the "good code, no computer to run it on" problem from
this attitude, but hey, it's a hobby.

For production code, I cheerfully assume POSIX or other standards.
(And, of course, *document* those assumptions.)

-s
--
Peter Seebach - [e-mail] - Copyright 1995 Peter Seebach.
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