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From: philip@axis.UUCP (Philip Peake)
Newsgroups: comp.lang.c
Subject: Re: Questions on X3J11 draft
Message-ID: <775@axis.UUCP>
Date: Sun, 7-Dec-86 06:03:19 EST
Article-I.D.: axis.775
Posted: Sun Dec  7 06:03:19 1986
Date-Received: Mon, 8-Dec-86 02:11:27 EST
References: <351@danews.ATT.COM> <7373@utzoo.UUCP> <3800@watmath.UUCP>
Reply-To: philip@axis.UUCP (Philip Peake)
Organization: Axis Digital, 135 rue d'Aguesseau, Boulogne, 92100, FRANCE
Lines: 47
Keywords: C,X3J11

In article <3800@watmath.UUCP> rbutterworth@watmath.UUCP writes:
>
>I can think of a perfectly conforming ANSI compiler that will break
>almost any existing C code.  Imagine a piece of code such as the following:
>    #include <stdio.h>
>    {
>        extern int getchar();
>        auto int c;
>        c=getchar();
>At the moment, this will blow up on (all?) existing C compilers since
>"getchar" is a macro.  Of course everyone KNOWS this and so never puts
>such things into their code.  But under ANSI, almost any function can
>be defined as a macro in the header files.  That means that almost
>any program that contains an "extern type libCfunc();" in it can
>potentially break under a conforming ANSI compiler.
>
>This change may or may not be a good thing; I don't know.
>I do know that my own coding style has changed drastically
>because of it.  I used to put explicit extern statements for
>all the functions I use, simply to document the fact that I
>am using them.  Now I NEVER put extern statements into ANY
>source.c file.

This is a *very* good point ! (Why didn't I think of it ? ......)

My personal coding style has changed considerably over the years, and
one of the directions in which it evolved was to ALWAYS put extern
declarations of any functions that I use. 

I started by putting them into a header file, this gets to be a pain,
since we either have a header file for each C file, or lots of redundant
extern declarations, and 'make' going beserk if you change one of the
declarations.

I now put them into the C file - I think its cleaner, and I like to be able
to find the type of a function when I am looking at a piece of code.

Taking the above example (sligthly modified), what if the function
actually returns something other than int ?

You HAVE to put the extern definition, if not other things will
probably (certainly ?) break.

How can I know, when trying to write portable code, if the 'library'
function I am going to use is a real function or a macro ?

Philip