The macro PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC appears near the top of several gc source files.

This has the effect of silencing gcc's complaints about format errors, both important and trivial. The important ones were fixed in JDK-8037816; the trivial ones remain, but as long as this macro remains in the file there is a potential for unchecked bit rot.

It's a tedious process, best done by someone who knows (or is learning) what was intended when type and format do not match.

It might be appropriate to work on this file using Zeno's algorithm; clear out the easiest half, and file another bug for the remainder.