Memory ``leaks'' in DEC servers

[rusty wright]

In article <2973 at bacchus.dec.com> joel at pandora.pa.dec.com (Joel McCormack) writes:

   From: joel at pandora.pa.dec.com (Joel McCormack)
   Newsgroups: comp.unix.ultrix
   Subject: Memory ``leaks'' in DEC servers
   Date: 7 Mar 90 01:15:45 GMT
   Organization: DEC Western Research Laboratory

   (1) There is no way to give memory back to the kernel once it is
   allocated.  So killing off all of your applications will not reduce the
   total amount of memory consumed by the server.  It should reduce the
   amount of memory needed to be resident.

This isn't true, a program can give memory back to the kernel once it
is allocated; do "man brk".  The problem is in the implementation of
malloc, realloc, and free.  Notice in the Ultrix man page for malloc,
et. al. that for free it says

	The argument to free is a pointer to a block previously
	allocated by malloc. This space is made available for further
	allocation, but its contents are left undisturbed.

I don't know why they do this, but I think it has something to do with
realloc or old code that tries to do what realloc does using free and
malloc.

Presumably one could write a different free, that really frees the
memory and returns it to the kernel via brk.  Version 19 of gnu emacs
is supposed to have something that does this; emacs also has a problem
of growing without bound since it keeps the entire file in memory.
--

--------------------------------------
	rusty c. wright
	rusty at violet.berkeley.edu ucbvax!violet!rusty