The old extension mechanism had several problems:
NODEstructure1 changed, an extension would have to be recompiled. Furthermore, to really write extensions required understanding something about gawk's internal functions. There was some documentation in this Web page, but it was quite minimal.
Despite the drawbacks, the xgawk project developers forked gawk and developed several significant extensions. They also enhanced gawk's facilities relating to file inclusion and shared object access.
A new API was desired for a long time, but only in 2012 did the gawk maintainer and the xgawk developers finally start working on it together. More information about the xgawk project is provided in gawkextlib.
 A critical central data structure inside gawk.