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From: allen@bunker.UUCP (C. Allen Grabert)
Newsgroups: net.unix-wizards
Subject: Bug in doscan.c
Message-ID: <378@bunker.UUCP>
Date: Thu, 19-Apr-84 10:03:48 EST
Article-I.D.: bunker.378
Posted: Thu Apr 19 10:03:48 1984
Date-Received: Fri, 20-Apr-84 01:25:36 EST
Lines: 18

Not being a regular reader of this newsgroup or an "experienced" systems
programmer, I have no idea if this bug has been noted before, but here goes.
'doscan.c', the common code for the 'scanf' routines, has a bug whereby a
program can go into an infinite loop.  One of our employees was reading
hex numbers and encountered an invalid hex digit; the program promptly
looped.  At roughly line 174 of the code there are the lines:
	if (c != EOF) {
		ungetc(c, iop); ...
The code assumes that a number has been decoded and the value of 'c' is the
character following the number.  However, the code should first check to see
if a number has actually been decoded or if the character is the first
character of the number.  One possibility is to insert the line:
	if (np == numbuf)
excuse me, make that:
	if (np > numbuf)
between the two lines mentioned above.  However, I am not in a position to
make a change and see if it works properly for a group of users, so please
take my suggestion as an educated guess.