The s2n-tls library must be initialized with s2n_init() before calling most library functions. s2n_init() will error if it is called more than once, even when an application uses multiple threads.
Initialization can be modified by calling s2n_crypto_disable_init() or s2n_disable_atexit() before s2n_init().
An application can override s2n-tls’s internal memory management by calling s2n_mem_set_callbacks() before calling s2n_init().
If you are trying to use FIPS mode, you must enable FIPS in your libcrypto library (probably by calling FIPS_mode_set(1)) before calling s2n_init().
We recommend calling s2n_cleanup() from every thread created after s2n_init() to ensure there are no memory leaks. s2n-tls has thread-local memory that it attempts to clean up automatically at thread-exit. However, this is done using pthread destructors and may not work if you are using a threads library other than pthreads.
A full cleanup and de-initialization of the library can be done by calling s2n_cleanup_final(). s2n-tls allocates some memory at initialization that is intended to live for the duration of the process, but can be cleaned up earlier with s2n_cleanup_final(). Not calling this method may cause tools like ASAN or valgrind to detect memory leaks, as the memory will still be allocated when the process exits.