[gentoo-server] Changing CFLAGS

[Karl Zander]

If I make changes to CFLAGS  in make.conf do I have re-compile everything 
with the new CFLAGS ?

     emerge -e world

Or can the existing packages use the CFLAGS they were compiled with and 
when I update packages or add new packages they would use the new 
CFLAGS.  Will Gentoo become unstable if mixed CFLAGS are used?   Same with 
USE....if I change USE flags will that cause harm to existing packages?

On the first Gentoo system I set up a few month ago I did not understand 
what CFLAGS and USE flags were all about so I did not change any of the 
defaults.  I would like to go back to adjust things now.

-Karl