Some libraries might register some handlers with pthread_atfork(). I don't need them as I only use fork() together with exec(). Also, they can cause trouble in some cases. So, is there a way to reset the registered handler list?
Related: calling fork() without the atfork handlers, fork() async signal safety.
POSIX does not document any mechanism for fork handlers installed by pthread_atfork() to be removed, short of termination of the process or replacing the process image. If you don't want them, then don't install them. If they are installed by a third-party library, as you describe, then your options are to find a way to avoid that behavior of the library (possibly by avoiding the library altogether) or to live with it.