Xref: utzoo comp.lang.c:9501 comp.sys.ibm.pc:14686
Path: utzoo!mnetor!uunet!husc6!uwvax!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c,comp.sys.ibm.pc
Subject: Re: Turbo C bug with unsigned long integer.
Message-ID: <11146@mimsy.UUCP>
Date: 21 Apr 88 02:24:39 GMT
References: <2658@im4u.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 23
Keywords: Turbo C, bug.

In article <2658@im4u.UUCP> demelo@im4u.UUCP (Julio De Melo) writes:
>		unsigned long variable;
>		...
>		variable = 1 << num_shift;
>	where :  num_shift < 32;
>	The problem is that if num_shift is higher than 14, I get
>(I suppose so) unnexpected results.

This is not a bug.  To get what you want, you must shift an unsigned
long 1, not an ordinary integer 1.  The result of `1 << num_shift'
is determined by the type of the left-hand operand of `<<', namely
`1'; the shift is thus done in integer precision.  Try

	variable = 1UL << num_shift;

or

	variable = (unsigned long)1 << num_shift;

(the former may not exist in various compilers).
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris