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From: roy@gitpyr.gatech.EDU (Roy Mongiovi)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Fragmentation on DOS - HELP !
Message-ID: <3617@gitpyr.gatech.EDU>
Date: Wed, 20-May-87 20:02:14 EDT
Article-I.D.: gitpyr.3617
Posted: Wed May 20 20:02:14 1987
Date-Received: Sat, 23-May-87 08:44:02 EDT
References: <287@pyuxv.UUCP> <764@usfvax2.UUCP>
Organization: Georgia Institute of Technology, Atlanta
Lines: 22
Summary: DOS frees all memory when a process terminates.

In article <764@usfvax2.UUCP>, chips@usfvax2.UUCP (Chip Salzenberg) writes:
> DOS does not reclaim these little blocks automatically.  Only the block that
> contains the program's Program Segment Prefix (PSP) is automatically freed on
> exit.  (Good thing, too, since to free your own code could be hazardous.)

This isn't at all true.  Each block of memory allocated via the DOS functions
has a 16 byte (1 paragraph) header which contains, among other things, the PSP
of its owner.  When a program terminates by any function except one of the
terminate and stay resident functions, all memory blocks owned by its PSP
are freed.

I don't understand the last quoted sentence.  How exactly could freeing the
code segment for the program that just terminated be hazardous?  That seems
to me to be exactly what ought to happen....

I sincerely hope that MSC does not use the DOS functions directly to allocate
memory, since 16 bytes is a tremendous overhead for small blocks.  I don't
own Microsoft C, so someone else will have to look into it.
-- 
Roy J. Mongiovi		Systems Analyst		Office of Computing Services
Georgia Institute of Technology		Atlanta GA  30332.	(404) 894-4660
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