dlsym is as specified in the
ISO/IEC 9945:2003 Portable Operating System(POSIX)and The Single UNIX® Specification(SUS) V3, but with differences as listed below.
The value RTLD_NEXT, which is reserved for future use shall be available, with the behavior as described in ISO/IEC 9945:2003 Portable Operating System(POSIX)and The Single UNIX® Specification(SUS) V3.