[brunoqc]

Do you know the difference between emacs-w64-25.1-Og.7z and emacs-w64-25.1-O2.7z. I'm guessing maybe one is a debug version and the other was build with -O2.

[jodoherty]

One has debugging symbols and the other was compiled with -O2 optimizations enabled.

[tbirdz]

gcc has a -Og option that performs all optimizations that don't interfere with debugging, so I'd guess that emacs..-Og is built using gcc's -Og option and emacs..-O2 is built using gcc with the -O2 option.