ruby--ruby/doc/mjit/mjit.md

MJIT

Here are some tips that might be useful when you work on MJIT:

Always run make install

Always run make install before running MJIT. It could easily cause a SEGV if you don't. MJIT looks for the installed header for security reasons.

--mjit-debug vs --mjit-debug=-ggdb3

--mjit-debug=[flags] allows you to specify arbitrary flags while keeping other compiler flags like -O3, which is useful for profiling benchmarks.

--mjit-debug alone, on the other hand, disables -O3 and adds debug flags. If you're debugging MJIT, what you need to use is not --mjit-debug=-ggdb3 but --mjit-debug.