[erlang-bugs] R13B-0, R12B-5 bug in erlang:memory/1

[Geoff Cant]

It appears that erlang:memory(processes_used) incorrectly return 0
instead of the value it returns when included in the erlang:memory()
result.

This behaviour occurs in R13B:

> {erlang:memory(), erlang:memory(processes_used), erlang:memory(processes), erlang:system_info(version)}.
{[{total,4354480},
  {processes,1104752},
  {processes_used,1100128},
  {system,3249728},
  {atom,308005},
  {atom_used,281638},
  {binary,18800},
  {code,2010109},
  {ets,136224}],
 0, % <--- incorrect
 1104752, % <--- correct
 "5.7.1"}

This behaviour also happens in R12B-5 as far as I can tell.

As near as I can tell the problem is here,
http://github.com/mfoemmel/erlang-otp/blob/master/erts/emulator/beam/erl_alloc.c#L1768
-- want.processes is not set and/or want.processes_used is not tested.

Cheers,
-- 
Geoff Cant