Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: How to find the problem in the object file
Date: Thu, 09 Feb 2017 15:20:52 -0800
Organization: None to speak of
Lines: 60
Message-ID: <lnvasjvtm3.fsf@kst-u.example.com>
References: <23ab01a2-5220-42cb-80b2-20a2b4a35d5c@googlegroups.com> <o6cut4$tfv$1@dont-email.me> <2beebc58-3f8f-46c6-bd10-e2ec3cf87906@googlegroups.com> <o6d0uj$5kt$1@dont-email.me> <lnfuk5eqeg.fsf@kst-u.example.com> <a84e9771-1ae7-4e4f-9602-259e6c25a7ce@googlegroups.com> <lny3xxd3ul.fsf@kst-u.example.com> <kfnfujwc1vn.fsf@x-alumni2.alumni.caltech.edu> <ln60ks78rd.fsf@kst-u.example.com> <kfna8a193yb.fsf@x-alumni2.alumni.caltech.edu> <lnshnt38oz.fsf@kst-u.example.com> <kfnfujo6ib1.fsf@x-alumni2.alumni.caltech.edu> <ln60kjz4ah.fsf@kst-u.example.com> <dfc2149d-356c-4bc4-a8ab-3954e4527ebd@googlegroups.com> <lno9ybxn52.fsf@kst-u.example.com> <874m03gnc5.fsf@news.bourguet.org> <35f03514-c25d-4372-bbaa-660d78ab7129@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Injection-Info: mx02.eternal-september.org; posting-host="be0e2eec6e3a3e421f62644bd2dd2876"; logging-data="25086"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19gD1bd/H6zR2bxb+qldR3Z"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux)
Cancel-Lock: sha1:+RtRqJnG0oTA5euxQHriiAXdHgw= sha1:gNfQgl3BEqP64N3Bw7DQopKDbhA=
Xref: csiph.com comp.lang.c:103578

supercat@casperkitty.com writes:
> On Thursday, February 9, 2017 at 1:45:45 PM UTC-6, Jean-Marc Bourguet wrote:
>> Keith Thompson writes:
>> 
>> > supercat writes:
>> >> On Thursday, February 9, 2017 at 11:01:55 AM UTC-6, Keith Thompson wrote:
>> >>> Do you have a compelling example where old-style function
>> >>> declarations are actually useful?  Perhaps you've already posted
>> >>> it here, but if so I can't recall it.  I also invite anyone else
>> >>> to post examples.
>> >>
>> >> On some systems, calls to prototyped functions use a different naming and
>> >> calling conventions from calls to non-prototyped functions.
>> >
>> > Name one.
>> 
>> Is this even conforming?  I though it was allowed to declare a function
>> with a prototype and define it without, without having the prototype
>> visible at the point of definition.
>
> I've observed such behavior with the Keil C51 compiler (which is non-
> compliant in a few ways, but strives to comply with the Standard as much
> as practical).

Then it's hardly relevant.

I believe this program is valid:

#include <stdio.h>

void func();

int main(void) {
    func("Hello, world");
}

void func(const char *message) {
    puts(message);
}

(The definition could be moved to a different translation unit if that
matters.)

At the point of the call, the only visible declaration of the function
is not a prototype.  The function is later defined with a prototype.  If
different calling conventions were used for prototyped and
non-prototyped functions, the call would likely fail somehow.

The change I propose making to the standard, removing non-prototype
function declarations and definitions, needn't affect any non-conforming
implementations if, for example, their non-conforming features are
sufficiently useful.  (I don't know why Keil would use different calling
conventions for prototyped and non-prototype functions, but I'll accept
that it does so and that there's some reason for it.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"