Compiled w/o using artifacts ff is either super-slow or crashes? need help

hi!

i’m a newbie wannabe contributor, right now I am trying to do some simple customization, and have problems building FF

  1. the fast build with --enable-artifact-builds runs fine

  2. once i started changing some .cpp files, I needed to run a “real” compilation

compiled with --disable-optimize - to speed compilation up - ff runs, but is unusably slow: 3-5-10 second after each key press / click (is it normal?)

  1. compiled with optimization, it crashes on startup - shows a dialogue for sending crash report but doesn’t show stack trace or any error (“stack overflow” / “segmentation fault” etc.) it says it is “attempting” to generate dump, but the specified directory remains empty. can post crash report details if it can help

  2. compilation with --enable-release fails with “dist/include/mozilla/dom/AnimationEffectBinding.h:86:58: error: field has incomplete type ‘OwningUnrestrictedDoubleOrString’” (why is this only a problem with this build setting?)

i have almost zero experience building huge projects of compiled code, probably need some advice

thanks in advance for any help