incorrect line returned (0) in rb_vm_get_sourceline()
If rb_vm_get_sourceline() is called when cfp->pc is equal to cfp->iseq->iseq_encoded (IOW, on the first instruction), then zero will be returned as the line number.
I think that if:
iseq->insn_info_size > 0, and,
iseq->insn_info_table.position == 0,
should be returned.