Comment 5 for bug 1202303

It ran out of space (which is what the first line of error output says "Heap exhausted during garbage collection: 1488 bytes available, 2064 requested").

300 million characters * at 4 bytes per character (we support the full unicode range) = 1.2 GB. Just representing the final string needs more than 200 MB more space than the 1GB heap.

You can increase the heap size with --dynamic-space-size. You might also want to consider working with octets or base-chars and :ascii or :iso-8859-1 external formats.