bug#37006: 27.0.50; garbage collection not happening after 26de2d42

[Eli Zaretskii <eliz@gnu.org>]

> From: Joseph Mingrone <jrm@ftfl.ca>
> Cc: Mattias Engdegård <mattiase@acm.org>,
>   eggert@cs.ucla.edu
> Date: Sun, 11 Aug 2019 17:28:11 -0300
> 
> > Thanks, I fixed this slightly differently, in a way that makes it more
> > explicit why we need a non-trivial code there.  Joseph, please see if
> > the latest master fixes the problem.
> 
> > (IMNSHO, this issue makes INT_ADD_WRAPV and friends unsafe; at the
> > very least this caveat should be prominently documented in Gnulib's
> > intprops.h.)
> 
> I have been running 94644d8 for the past hour or so and resident memory for the Emacs process is up over 1300 MB.  Also with `garbage-collection-messages' set to t, I do not see any messages about garbage collection.

Are you saying that the fix didn't solve the problem for you?  I
definitely saw a lot of GC messages after the fix where I didn't
before.  For example, if you visit xdisp.c from the Emacs sources and
page through it with C-v, don't you see a lot of GC messages?

> I should also add that after my initial report, running 26de2d42, I did eventually start seeing garbage collection messages and the memory usage stopped increasing.  Something must have triggered garbage collection to start again.

After a lot of consing, the GC would come back for a while, until it
would be effectively disabled again by some opportune code path.

If you see no GC messages for a long time, attach a debugger and look
at the value of consing_until_gc.  If its value is huge, around
LONG_MAX, the problem is still not completely solved.