Odd sharing of files between forked processes

[alindeman]

Consider:

require 'tempfile'

out = Tempfile.new("abc")

File.open("/tmp/hello.rb", "w") { |f| f << "File.open('#{out.path}', 'a') { |f| f << 'first!' }" }
pid = fork { exec(["./bin/rbx", "./bin/rbx"], "/tmp/hello.rb") }
Process.waitpid(pid)

File.open("/tmp/hello.rb", "w") { |f| f << "File.open('#{out.path}', 'a') { |f| f << 'second!' }" }
pid = fork { exec(["./bin/rbx", "./bin/rbx"], "/tmp/hello.rb") }
Process.waitpid(pid)

puts File.read(out.path) # => first!first!

first!second! is expected.

$ ruby -v
rubinius 2.0.0.rc1 (1.8.7 00f249f8 yyyy-mm-dd JI) [x86_64-apple-darwin12.4.0]

Also reproducable with RBXOPT=-X19

[dbussink]

I've updated the issue with different paths to call rbx, since I was totally confused at first that this worked fine, but it was invoking MRI on my system, since ruby executes MRI here for me by default

[dbussink]

Ok, this seems to have nothing to do with forking, but with a problem with our compiled code caching. If I do the following, it works correctly for me:

export RBXOPT=-Xcompiler.no_rbc

This basically disables caching compiled Ruby code. For some reason it doesn't see /tmp/hello.rb as being changed, so it runs the cached version the second time even through it's obviously not correct there since the script has changed.

[alindeman]

Ok, this seems to have nothing to do with forking, but with a problem with our compiled code caching. If I do the following, it works correctly for me:

export RBXOPT=-Xcompiler.no_rbc

This basically disables caching compiled Ruby code. For some reason it doesn't see /tmp/hello.rb as being changed, so it runs the cached version the second time even through it's obviously not correct there since the script has changed.

Perfect, thanks for isolating it further. The bug manifested itself in some of my code that forked, so it's the example I was able to isolate.

What does Rubinius use to determine if code needs to be recompiled? Maybe it's related to timing if it's using something like file mtime.