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From: jiml@uwslh.UUCP (Jim Leinweber)
Newsgroups: net.unix
Subject: Re: get size of malloc'd object
Message-ID: <139@uwslh.UUCP>
Date: Tue, 24-Jun-86 12:15:15 EDT
Article-I.D.: uwslh.139
Posted: Tue Jun 24 12:15:15 1986
Date-Received: Thu, 26-Jun-86 04:07:09 EDT
Organization: U of Wisconsin-Madison, State Hygiene Lab
Lines: 20

One nasty efficiency quirk probably ought to be mentioned.  The schemes which
add extra user information to remember the size of the object are okay,
modulo some pointer alignment details.  Care with the size of the objects
may be needed if you are allocating lots of them, though.  Some memory
allocators allocate things in fixed sizes, such as power-of-two minus some
internal overhead. If a program is allocating funny sized buffers scaled to
cooperate with brain damaged allocators, and then adds extra overhead, the
resulting size may cause poor allocators to waste lots of space.  Of course,
'knowing' the size of blocks actually allocated is not portable. But if you
are tight on address space or physical memory, it could matter.

Jim Leinweber   			usenet:  jiml@uwslh.uucp
State Hygiene Laboratory        	  {seismo, harvard, topaz, ihnp4,...}!
University of Wisconsin			  uwvax!uwslh!jiml
465 Henry Mall				internet:    uwslh!jiml@wisc.edu
Madison, Wisconsin, USA  53706		phone:   (608) 262-8092
-- 
James E. Leinweber   ...!{seismo,harvard,topaz,ihnp4}!uwvax!uwslh!jiml
Wisconsin State Hygiene Lab          (608) 262-8092
University of Wisconsin; 465 Henry Mall; Madison, WI  53706