Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!apple!voder!nsc!amdahl!JUTS!ruts!msh30
From: msh30@ruts.ccc.amdahl.com (Mark Hahn)
Newsgroups: comp.lang.c
Subject: Re: Question about assertion macro
Message-ID: <17N902t808i701@JUTS.ccc.amdahl.com>
Date: 1 Jun 91 00:57:52 GMT
References: <1991May29.152228.27611@viewlogic.com>
Sender: netnews@ccc.amdahl.com
Reply-To: msh30@RUTS.ccc.amdahl.com (PUT YOUR NAME HERE)
Organization: Amdahl Corporation, Sunnyvale CA
Lines: 48

>From: greg@suntan.viewlogic.com (Gregory Larkin)
>
>
>Hi there,
>
>I would like to construct an assertion macro so that I
>can print the exact condition that failed as a string.
>
>Here is the way I call the macro:
>
>ASSERT(foo != NULL, "Unexpected NULL pointer");
>
>And here is how it is currently defined:
>
>#define ASSERT(relation, msg) { if(!(relation)) { \
>			      printf("ASSERTION FAILED: File %s Line %d %s\n",\
>                                     __FILE__, __LINE__, msg); \
>			      exit(FatalError); } }
>
>I would like to expand the macro so that I can print the message as:
>
>ASSERTION FAILED: foo != NULL, File xxxx Line yyyy Unexpected NULL pointer
>
>How can I print the string "foo != NULL" without passing in the test as
>a string.  Can I print the test directly as a string somehow?
>
>Thanks for any help,
>-- 
>Greg Larkin (ASIC Engineer)|"This is a fragile ball we are living on; 
>Viewlogic Systems, Inc.    |it's a miracle and we are destroying it.."
>293 Boston Post Road West  |Peter Garrett, Midnight Oil               
>Marlboro, MA 01752  (greg@Viewlogic.COM)

#define ASSERT_ARG(relation, msg, action) \
if ( !(relation) ) { \
  printf("ASSERTION FAILED: File %s Line %d %s %s\n",\
  __FILE__, __LINE__, "relation", msg);\
  action; \
} /* if assertion failed */

should work in standard C; I'm not sure about ANSI C, though.
This version has the advantage of being able to specify a C
statement as an action to be taken rather than calling exit(),
which is useful if you need to clean up some things first.

Usage:
  ASSERT_ARG( foo != NULL, "Unexpected NULL pointer", 
              cleanup_routine(arg1, arg2, ..., argn) );