[ruby-core:75129] [Ruby trunk Bug#12305] "can't remove str from str_id" at unregister_sym

Issue #12305 has been updated by Robert A. Heiler.


I think it is difficult to track it down if it only appears sometimes.

Perhaps you find some way to trigger it more often - if you don't see a pattern in the bug occurrence,
perhaps you can find a pattern in the ruby code that triggers it ultimately.

The C code for the bug should be here in the function unregister_sym():

    https://github.com/brightbox/deb-ruby2.3/blob/master/symbol.c#L395

I am not sure who or what tries to unregister a symbol but I think you will
find some patterns in the coming days/weeks. Heisenbugs sometimes require
detective work.

----------------------------------------
Bug #12305: "can't remove str from str_id" at unregister_sym
https://bugs.ruby-lang.org/issues/12305#change-58261

* Author: Konstantin Starodubtsev
* Status: Feedback
* Priority: Normal
* Assignee: ruby-core
* ruby -v: ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
I'm experiencing random occurrences of "can't remove str from str_id" crash.

Message string looks like this one:

```
/srv/sim/.rvm/gems/ruby-2.3.0@env-manager/gems/mongo-2.2.4/lib/mongo/server/description.rb:508: [BUG] 0x007f4f400ab310 can't remove str from str_id (`..dO.)
```

The only constant thing in it is the "can't remove str from str_id" substring. Other things like address, source code location or symbol string value in brackets differ between crash reports (see attachments).

In a C level backtrace information the only common part is top of a trace:

```
-- C level backtrace information -------------------------------------------
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(rb_vm_bugreport+0x51f) [0x7f4f8b0106ff] vm_dump.c:688
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(rb_bug+0xcf) [0x7f4f8ae9a01f] error.c:420
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(unregister_sym.part.12+0x20) [0x7f4f8ae4aada] symbol.c:399
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(rb_gc_free_dsymbol+0x62) [0x7f4f8afa56a2] symbol.c:637
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(gc_sweep_step+0x621) [0x7f4f8aec0d01] gc.c:2211
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(heap_get_freeobj_from_next_freepage+0x72) [0x7f4f8ae498c3] gc.c:3624
/srv/sim/.rvm/rubies/ruby-2.3.0/lib/libruby.so.2.3(newobj_slowpath_wb_protected+0xf4) [0x7f4f8aec43d4] gc.c:1679

We hit this bug at least once per day, so should you need any other information, let me know.
```

Attached are three full [BUG] reports for three different occurrences.



---Files--------------------------------
report-01.log (247 KB)
report-03.log (251 KB)
report-02.log (266 KB)


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