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From: mccrady@torolab6.vnet.ibm.com ("Don McCrady")
Newsgroups: comp.lang.c
Subject: Re: Question about assertion macro
Message-ID: <9106031304.AA28761@ucbvax.Berkeley.EDU>
Date: 3 Jun 91 13:11:34 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 35

>>From: greg@suntan.viewlogic.com (Gregory Larkin)
>>I would like to construct an assertion macro so that I
>>can print the exact condition that failed as a string.
>>   ASSERT(foo != NULL, "Unexpected NULL pointer");
>>Greg Larkin (ASIC Engineer)

> #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.
> From: msh30@ruts.ccc.amdahl.com (Mark Hahn)

No, this won't work in ANSI C... If you use an ANSI C preprocessor,
you can do this easily with the "stringize" operator, #... Try this:

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

Better yet, if you have an ANSI compiler, you should have a header
file called <assert.h>, which will do exactly what you want; that
is, print the failing assertion, the file and line number, and call
the abort() function to terminate the program.

Enjoy.

             ++Don;