As Norvald wrote in his recent post:

A long time ago, libmysqlclient came in two versions: one that was thread safe and one that wasn’t. But that was a long time ago. Since MySQL 5.5, the thread safe libmysqlclient_r library has just been a symlink to the libmysqlclient library, which has been thread safe at least since then.

…

We plan to hide (not export) the symbols of the SSL library used by the MySQL client library. As step one in that effort, we plan to hide all of the non-documented symbols because we want to stop polluting the MySQL client program’s namespace.

Consider a requirement where there the OpenSSL and MySQL client library functions are both used directly to generate a binary. If the order of linking used is 1. MySQL client library (i.e libmysqlclient) and then 2. OpenSSL library (i.e libcrypto), then using the created binary will result in a crash.

The Reason why it will crash is as follows: The libmysqlclient library already has the built-in yaSSL library and has exported its symbols. The yaSSL and OpenSSL libraries share some of the same symbol names, so the executable which is prepared in the above said order, will resolve the OpenSSL symbols indirectly using the libmysqlclient library (yaSSL) rather than using …