In what cases does an undefined symbol error occur in linux libraries?

Question

linux

In what cases does it happen that an undefined symbol error occurs when loading a library?
Library function not found?

Answer 1

How to debug this process?

By setting the environment variables LD_DEBUG and LD_DEBUG_OUTPUT before running the program and looking at the resulting log. See man ld.so .

Answer 2

As a rule - when either is too old and the program refers to it as new - usually occurs when the author of the lib is a weirdo and does not increase the build number. Or vice versa - the old source is linked to the new one, the new one doesn't have such names anymore.