Programs become unstable in the context of the broader system they operate within, so for example I typically use high performance tweaks even for general desktop usage, and so programs can become unstable simply because of that context, and stutter, fail to load, crash, display artifacts, even weird behavior like in gaming.
The firefox I’m using now does not use -03 but -02, and in my experience, when I tried to compile it in the past, on a funtoo system with -03, because I thought hey, I want it to be faster, firefox became unstable just as the OP is describing.
I don’t think it’s appropriate for apps to default to -03 based on my experience, because they will become unstable, and unreliable, which isn’t always obvious. But, try running many tabs at the same time, multiple instances, like you might infrequently when using firefox, or cranking up the volume on the underlying systems performance, and watch firefox start to suffer.
this is really neat though, thanks for that piece of info…
about:buildconfig
