Bug #17268
closed
special global variables which can be accessed from ractors
Description
Ractors can't access global variables, but some special global variables should be accessed.
There are several types.
Proposal¶
(1) Read-only global variables
# process-local (readonly): other commandline parameters '$-p' => $-p, '$-l' => $-l, '$-a' => $-a, # process-local (readonly): getpid '$$' => $$, (2) scope local variables
# thread local: process result '$?' => $?, # scope local: match '$~' => $~.inspect, '$&' => $&, '$`' => $`, '$\'' => $', '$+' => $+, '$1' => $1, # scope local: last line '$_' => $_, # scope local: last backtrace '$@' => $@, '$!' => $!, (3) Ractor local variables
# ractor-local (derived from created ractor): debug '$DEBUG' => $DEBUG, '$-d' => $-d, # ractor-local (derived from created ractor): verbose '$VERBOSE' => $VERBOSE, '$-w' => $-w, '$-W' => $-W, '$-v' => $-v, # ractor local: stdin, out, err '$stdin' => $stdin.inspect, '$stdout' => $stdout.inspect, '$stderr' => $stderr.inspect, Implementation: https://github.com/ruby/ruby/pull/3670
I'll merge it soon.
Discussion¶
- only accessible from main ractor?
-
$0: - ARGV, ARGF,
$.
-
- only accessible from main ractor because they will be obsolete
$, $/ $; $\
- So difficult:
$" / $LOADED_FEATURESand$: / $LOAD_PATH
Updated by ko1 (Koichi Sasada) about 5 years ago
- Description updated (diff)
Updated by ko1 (Koichi Sasada) about 5 years ago
- Status changed from Open to Closed
Applied in changeset git|99310e3eb56fbc85bb45119285812eb959448d0c.
Some global variables can be accessed from ractors
Some global variables should be used from non-main Ractors.
[Bug #17268]
# ractor-local (derived from created ractor): debug '$DEBUG' => $DEBUG, '$-d' => $-d, # ractor-local (derived from created ractor): verbose '$VERBOSE' => $VERBOSE, '$-w' => $-w, '$-W' => $-W, '$-v' => $-v, # process-local (readonly): other commandline parameters '$-p' => $-p, '$-l' => $-l, '$-a' => $-a, # process-local (readonly): getpid '$$' => $$, # thread local: process result '$?' => $?, # scope local: match '$~' => $~.inspect, '$&' => $&, '$`' => $`, '$\'' => $', '$+' => $+, '$1' => $1, # scope local: last line '$_' => $_, # scope local: last backtrace '$@' => $@, '$!' => $!, # ractor local: stdin, out, err '$stdin' => $stdin.inspect, '$stdout' => $stdout.inspect, '$stderr' => $stderr.inspect, 
Updated by Dan0042 (Daniel DeLorme) about 5 years ago
Why can't ractors access global variables? Shouldn't it be like constants, where a frozen/shareable object can be accessed?
$x = [1,2,3] Ractor.new{ $x }.take # I understand that this can't work $x = true Ractor.new{ $x }.take # but why is this not ok? 
Updated by Eregon (Benoit Daloze) about 5 years ago
I think this issue is mostly about "special" global variables, not so much about "regular" global variables.
I wonder if "regular" global variables should be Ractor-local, or behave like constants.
Since most of the above became Ractor-local (instead of per-Process before) or a narrower scope, I think Ractor-local would make most sense.
The only special variables that are still process-local are read-only, which means it's the same as if they were Ractor-local read-only.
Updated by Dan0042 (Daniel DeLorme) about 5 years ago
Eregon (Benoit Daloze) wrote in #note-4:
I wonder if "regular" global variables should be Ractor-local, or behave like constants.
I wouldn't mind either way. Although if Ractor-local I would hope they are derived from created ractor, like $DEBUG and $VERBOSE.
Updated by ko1 (Koichi Sasada) about 5 years ago
The proposal is accepted.
I wonder if "regular" global variables should be Ractor-local, or behave like constants.
This is rejected at first by Matz (my original proposal is making all $gvars are ractor-local), to avoid confusion.