The tricky thing with library versioning that you get into is when types change. Let's say my app uses libc and libfoo, both from the underlying operating syst

The tricky thing with library versioning that you get into is when types change. Let's say my app uses libc and libfoo, both from the underlying operating system / distribution. libc has a 32 bit time_t, and libfoo on my system also has a 32 bit time_t. I upgrade to a new operating system where both libc and libfoo have 64 bit time_t. libc was kind enough to include symbol versioning which makes time(NULL) return a 32 bit number to my binary. Now, libfoo either has to be patched to handle symbol versioning and have a new version inside so that my app can get the old 32 bit time_t, or it will have a subtly broken ABI. The thing is-- who does this? Libfoo doesn't know when each distro will make the change: it won't correspond to a specific upstream version. Does each distro have to recognize the issue and introduce symbol versions? Etc.