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Path: utzoo!utgpu!water!watmath!orchid!rbutterworth
From: rbutterworth@orchid.UUCP
Newsgroups: comp.lang.c
Subject: Re: Second question on #define
Message-ID: <11570@orchid.waterloo.edu>
Date: Thu, 5-Nov-87 09:42:42 EST
Article-I.D.: orchid.11570
Posted: Thu Nov  5 09:42:42 1987
Date-Received: Sat, 7-Nov-87 15:51:04 EST
References: <10104@brl-adm.ARPA>
Organization: U of Waterloo, Ontario
Lines: 25

In article <10104@brl-adm.ARPA>, ultra!wayne@ames.arpa (Wayne Hathaway) writes:
> I have a large number of manifest constants of
> the form
>                     GREATBIGLONGPREFIX_SHORTTHING
> I would like to have a macro accept only SHORTTHING as an argument but
> use the full constant name in the generated code.  I (naively) tried
>         #define   WIDGET(x)   printf("%d\n", GREATBIGLONGPREFIX_x)
> but of course this didn't work (didn't substitute x).

Put the following into your common header file:
    #if defined(__STDC__)
    #   define JOIN(x)x##
    #else
    #   define JOIN(x)x
    #endif

Then, you can do things like
    #define WIDGET(x) printf("%d\n", JOIN(GREATBIGLONGPREFIX_)x)

This works on all the cpp implementations I've used.

If you find one that it doesn't work for, you only need to add
another condition for the definition of JOIN in the header
file to make it work the way that that cpp wants it, and you
don't have to change any of your source code.