Heap Problem

I've seen an issue where sometimes an object will not be retained, however calling GC.start will not clear it out of the heap. This repo shows that issue.

Run via

$ ruby run.rb

This will run both the "fail" case that demonstrates the problem and a "pass" case that uses puts and 10.times { GC.start } to fix the issue.

$ ruby run.rb
== Calling `puts` and `10.times { GC.start }
  Address of string is: 0x7fa94c091468

  PASS expected: 0 actual: 0

== Calling only `GC.start`
  Address of string is: 0x7f897d04d400
  Found in heap dump:
    {"address":"0x7f897d04d400", "type":"STRING", "class":"0x7f897d04d298", "embedded":true, "bytesize":15, "value":"i am a string 2", "encoding":"UTF-8", "file":"fail.rb", "line":12, "method":"run", "generation":8, "memsize":40, "flags":{"wb_protected":true, "old":true, "uncollectible":true, "marked":true}}

  FAIL expected: 0 actual: 1

You can call individual files if you want

$ ruby fail.rb
$ ruby pass.rb

The only difference between the two files is this:

$ diff fail.rb pass.rb
28c28,29
< GC.start
---
> @stringio.puts "=="
> 10.times { GC.start }

Tested with Ruby 2.3.3p222 and 2.4.0preview3.