Possible bug in 4.2 BSD csh

[phb at dcdwest.UUCP]

We have noticed a case where a csh shell script which contains a loop
that runs for many hours (sometimes, days even) accumulates all the
free memory on the system and causes the vax to brought to its knees
due to paging activity.  The RSS (resident set) of the shell expands
to over a thousand pages (40-50% of the availible memory on a
4 MB memory vax).  This shell script makes heavy use of variables and
in-line command execution (e.g., set N = `pwd`, etc.) but none of
the output of these commands which are read into shell variables
are more than a hundred bytes.

Since the RSS remains as high as the total size, it seems that csh
is touching all the pages regularly.  In a preliminary examination of
the shell's memory allocation code, this type of behavior would be
quite possible as the shell scans its list of memory blocks in the
"alloc" routine.  The bug appears to be that it never reuses memory
found during the scan but continually allocates more.

Has anyone else noticed and/or fixed this type of bug in 4.2 BSD csh code?
If so we would apprecicate hearing about it before we start digging into
csh's memory allocation code ourselves.

					Peter H. Berens
					ITT Defense Communication
					San Diego, CA
					(619) 578-3080 x240
		decvax!ittvax!dcdwest!phb or ucbvax!sdcsvax!dcdwest!phb