How do I upgrade glibc without breaking dependinces?
Glibc libraries are essential for having Linux work properly, so what you're asking is something like asking how to renovate the foundation of a building without moving the structure on top of that first.
Warning: I used the next procedure with some libs but never with Glibc tho, so YMMV(VM). If you feel upgrading Glibc will be like doing open heart surgery, make a backup first and have a rescue CD/floppy ready, Justin Case. Make a local copy of /etc/ld.*. Copy the Glibc libraries to a new dir, call it /usr/lib_old or so. Add that path in /etc/ld.so.conf. Run ldconfig and check if it's added the path. Now remove the original Glibc path from /etc/ld.so.conf and update running ldconfig. You'll find out if this will work soon enough :-]
If it works, test upgrading Glibc. If satisfied, install. Check if old apps still work.