Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!littlei!donk!ajw
From: ajw@donk.UUCP (ajw)
Newsgroups: comp.lang.c
Subject: Usual arithmetic conversions
Keywords: sizeof unsigned ouch
Message-ID: <308@donk.UUCP>
Date: 22 May 89 18:57:25 GMT
Organization: DTE, Intel Corporation; Hillsboro, OR
Lines: 17

Don't you just hate it when code that has been working for years
suddenly goes bad on you?  This took a few merry hours to find:

if (buf_size - (used_so_far + this_record_size + trailer_size) >= 0)
	enough_room_left();

"trailer_size" is in fact #defined as an expression which deep in its
bowels includes a 'sizeof'.  My new compiler (quite properly, I have no
doubt), treats 'sizeof' as unsigned, with the result that the entire
expression in the 'if' statement becomes unsigned, and thus the condition
is always true.

Trivial, I know, but hey, it beats chundering on about summing pointers.

-- Alan Waldock, just offering individual opinions while happening to work at 
Intel Corp, M/S HF2-37, 5200 NE Elam Young Pkwy, Hillsboro, Oregon 97124-6497
ajw@aus.hf.intel.com   ...uunet!littlei!intelhf!aus!ajw  "Live malloc or die"