how has C bitten you?

[Bob Peirce]

Here's one that trapped me this week.  It took much head scratching
and debug prints to figure it out.

int dial(telno)
char *telno;
{
	if(telno){		/*  should be if(*telno)  */
		dial it;
	}
	else{
		hang up;
	}
}

Print statements showed the telno was being handed to the routine,
but the if said nothing was there.  Turns out, on my system, the
address of telno is NULL.  I needed to check the contents not the
address!
-- 

		 	Bob Peirce, Pittsburgh, PA
		uucp: ...!{allegra, bellcore, cadre, idis}
		  	 !pitt!darth!investor!rbp
				412-471-5320

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