Linux applications almost always use dynamic linking to the C library, meaning it is not compiled into them -- it is linked at runtime. This means if you have upgraded the C library, you should not have to do anything else.
However, while it would be very unusual, it is not impossible for things to be built with a statically linked glibc. The best thing to do is just look at the documentation for the application in question. If this is the practice, it is almost certainly explicit.
You can check executables with
file. It should say "dynamically linked" in the output. I think it is still possible for such a binary to then incorporate a static glibc -- but this would be incredibly obtuse. The way to double check would be:
ldd whatever | grep libc.so
whatever is the binary you want to check. You should get some output. If not, leave a comment here so I can eat my hat because I don't believe anyone would create such a thing.
If you do find an actual static binary, this does not mean it necessarily used glibc. You'd have to confirm that by consulting the source tree, documentation, or developers.
I've read that some people had to revert the update bcos they faced segfaults in their apps.
I've seen that second and third hand too. I haven't actually seen a concrete description of such a case though. I think it is very unlikely, to be honest.