[gentoo-user] What is the correct way to remove an old gcc-version (emerge --depclean) ?

Hi,

on my embedded system I currently ran into a problem:

As adviced after a greater world update I did 

    emerge --depclean -vp

beside other stuff sys-devel/gcc was shown as candidate
for removal. An old version was shown for removal and
a newer one was shown as preserved.

I checked with eselect, whether the new version was selected
(it was), made a backup and started emerge --depclean -v.

As soon it has removed gcc, a firework of error brightened
my terminal...beside other things the shell failed while
trying to access libgcc (if I had recognized that correctly...).

Technically no problem: I stopped that, cleared the sdcard
and installed the backup...but what did I wrong here?

What is the correct way to handle such things?

Best regards,
Meino