Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!samsung!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.soft-sys.andrew
Subject: "doload_preset" doesn't zero out BSS it allocates?
Message-ID: <2662@auspex.auspex.com>
Date: 23 Nov 89 01:35:58 GMT
Reply-To: guy@auspex.auspex.com (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 30

"doload_preset" in all the versions of "doload.c" in the R4 beta version
of Andrew (except the Apollo one, which doesn't have to bother with all
that stuff since the Apollo OS already has a dynamic loading mechanism)
handles commons in a ".do" file by "malloc"ing up some space.  However,
it doesn't zero out that space, which means it doesn't have the UNIX
semantics of commons.

I suspect this may ultimately be the cause of the hang in "help",
reported a while ago and fixed by a workaround involving moving some YP
and RPC stuff into "libcx.a".  The problem appeared ultimately to have
been caused by some BSS location not being zero, so this points in the
direction of this bug; moving the YP/RPC stuff into "runapp" left it up
to "ld", not "doload", to zero its commons out, which it does.

It may also be the cause of some problems I saw with "console", which
also appeared to have been caused by some BSS location not being zero
and which were fixed by explicitly initializing some items in
"console/lib/initglbs.h" to zero, so that they're no longer commons.

It appears that the whole reason "console/lib/initglbs.h" exists in the
first place is to move a bunch of stuff out of BSS, perhaps so that it
*is* zeroed properly.  Is it the intent that "doload" *not* zero out
BSS?  If so, this can certainly be worked around by Andrew code, using
that very technique, but it can't be worked around by code pulled in
from "libc", etc., since you have no control over that code; it would
therfore seem that not having "doload" zero out BSS would be
undesirable.

Is this a performance issue?  It already calls "malloc" for each common
anyway; does adding a call to "bzero" make things noticeably worse?