From: kunst AT prl DOT philips DOT nl
Subject: preprocessor cryptics
To: djgpp AT sun DOT soe DOT clarkson DOT edu (DJGPP users list)
Date: Thu, 20 Jan 1994 14:33:20 +0100 (MET)


I would like to post a hint for DJGPP users in case they encounter
a compilation error of the kind (see the test program below for details):

   c:/tmp/cc016065:1: parse error before `.'
   c:/tmp/cc016065:305: malformatted character constant

I took me quite some time already in a few instances to track the source
of such error. I make use of various libraries, not all written by myself
ofcourse, which come with their own include file(s) and #defines. 
The fact that include files may be nested makes the troubleshooting even
more difficult...

I don't know if this behaviour is specific for the DOS version of gcc
since I only have an older version of gcc running on our HP-UX machine.
I suspect however that this behaviour has shown up since the latest
versions of gcc. Needless to say I prefer the more versatile message
of gcc version 2.4.5.  I have included a small test program below.

The hint: check your #defines against those of others !

Regards,

 .^^^^^^^^           _____________________________________
 |      |          / Pieter Kunst (P.J.)                   \
 |  _  _|        /   Philips Research Laboratories,          \
.--(o)(o)      /     Building WY3, Prof. Holstlaan 4,         \
|@      _)   /       5656 AA  Eindhoven, The Netherlands.      |
  | ,___|   /        e-mail: kunst AT prl DOT philips DOT nl             /
  |   /     \_______________________________________________/
  /____\

---------------------------------- test.c -------------------------------------
/*
 * "Preprocessor cryptics"
 *
 * If the two defines are equal, no warning is given (with 'gcc -Wall').
 * This second, equal definition is allowed. See K&R, 2nd ed., p.229:
 *
 *   "A second #define for the same identifier is erroneous unless the
 *    second token sequence is identical to the first, where all white
 *    space separations are taken to be equivalent."
 *
 * If they are unequal however, the following error is reported by gcc:
 * (DJGPP 1.11, gcc 2.5.7)
 *
 *   c:/tmp/cc016065:1: parse error before `.'
 *   c:/tmp/cc016065:305: malformatted character constant
 *
 * HP-UX 'cc' gives: test.c: 29: warning- Redefinition of macro TRUE.
 *
 * HP-UX 'gcc' (old version, 2.4.5) gives:
 *   test.c:29: warning: `TRUE' redefined
 *   test.c:27: warning: this is the location of the previous definition
 *
 */

#include <stdio.h>

#define TRUE  1    /* first definition */

#define TRUE  2    /* second definition differs */

int main ()
{
  printf ("TRUE = %d\n", TRUE);
  return 0;
}