This is a preparatory step for the Leyden project.

Currently ClassListParser has a hard-coded limit of 4096 characters for each line in the CDS classlist

https://github.com/openjdk/jdk/blob/0b01144ecec1283adaaaf1a7f53d075a56f030ae/src/hotspot/share/cds/classListParser.hpp#L84-L88

With Project Leyden, we expect to store more information in the classlist that may exceed this limit. For example, JDK-8293980 add the list of pre-resolved constant pool entries for each class in the classlist. The line length can theoretically be tens or thousands of characters, if not more.

We should remove this hard-coded limit and dynamically allocate a buffer for reading long lines up to a reasonable limit (this RFE sets the limit to 4M chars).