[gentoo-user] how to keep the souce for debugging under gentoo?

[fei huang]

I posted a question a while ago regarding the way of debugging /sbin/init .
I managed to do it by adding -ggdb to CFLAGS temporarily (as well as the
nostrip feature).

 however, I found the source from /usr/portage/distfiles does not match the
running instance, then I realized that the running executable is compiled
from patched or altered version of source files. Is there a way to get the
matching source?  if there exists a solution, it might be applied to all
applications under gentoo that to be debugged, i think..

tks

daniel