id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
2583	printf %s is not lazy enough	olsner		"Taking a fixpoint of printf {{{fix (printf ""a%s"") :: String}}}, or printf'ing an infinite string {{{printf ""%s"" (repeat ' ') :: String}}} either fails with stack overflow or diverges.

The culprit is in this code:
{{{
fmt cs us =
	let (width, prec, ladj, zero, plus, cs', us') = getSpecs False False False cs us
	    adjust (pre, str) = 
		let lstr = length str
		    lpre = length pre
		    fill = if lstr+lpre < width then take (width-(lstr+lpre)) (repeat (if zero then '0' else ' ')) else """"
		in  if ladj then pre ++ str ++ fill else if zero then pre ++ fill ++ str else fill ++ pre ++ str
}}}

If width == 0, then no filling should be done, but the code is still forcing the evaluation of lstr and lpre (which in the case of an infinite str does not ever complete). A simple fix is to check that width is larger than zero before trying to test width against lstr and lpre, like this:

{{{
fill = if width > 0 && lstr+lpre < width then {-etc-}
}}}"	bug	closed	low	7.0.1	libraries/base	6.8.3	wontfix			Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown