use of if (!cptr) and if (cptr), where cptr is a *

[Eric Giguere]

The following quote from the draft ANSI Standard should be of interest:

  "An integral constant expression with the value 0, or such an expression
   cast to type void *, is called a null pointer constant." (3.2.2.3)

and then later

  "NULL ... expands to an implementation-defined null pointer constant" 
  (4.1.5)

So even if your compiler uses its own non-zero internal representation
for the null pointer, it must be able to catch expressions of the form

     if( ptr != 0 )
     if( ptr != ( 10 * 10 - 101 + 1 ) )
     if( ptr != (void *) (5-5) )

and your macro for NULL better expand to a zero-valued integer expression.

Eric Giguere                                  268 Phillip St #CL-46
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