My webzone

A place for John Bintz to ramble.

RVM, the JSON gem, the @global gemset, and rb_gc bugs

Upon building Ruby 1.9.3-p125 on my Snow Leopard Mac and getting ready to take it for a spin, trying to run anything of note in a Rails app brought the following cryptic error:

[BUG] cross-thread violation on rb_gc()
(null)

Abort trap

Digging into Console.app, the backtrace indicated that the system libruby.1.dylib was being accessed from the C parser in the json gem living in the @global RVM gemset. otool -L confirmed that the parser in the @global gemset was linked against system ruby, not RVM ruby. Installing a new json gem into the current gemset didn’t work, as RVM prefers to use the @global version of the gem over the one in the current gemset, it seems. Deleting the gems from the @global gemset and reinstalling the json gem in the current gemset worked, and I’m sure I could have reinstalled the json gem globally too.