[caf]

glibc goes to great lengths to ensure binary backwards-compatibility. If a binary interface has to change it uses symbol versioning to keep around the old interface - for example if you have a program compiled against glibc2.2 on x86-64 that calls timer_create(), it will call through the function __timer_create_old() that provides the old interface when run on a system with a newer libc.

The reverse scenario that seems to be what you have - where you compile against a newer library version then run it on an older one - is forwards-compatibility which is a different kettle of fish. Even on Windows it's not like you can compile against the latest DirectX and run it on an older Windows?