Consider the file rubyfile.rb, which only contains an = sign, a clear syntax error.
$ mrbc -c rubyfile.rb
rubyfile.rb:1:2: syntax error, unexpected '='
I tried debugging for a long time, and from what I've observed in the stack trace, the sym that appears to correspond to SyntaxError, 243, gets discarded during/after the first call to const_get in src/variable.c. Eventually 245, which seems to correspond to NameError, takes its place. I wasn't able to fix the issue.
mrb might be intialized incompletely from mrbc; close #457