C.3.2 Extension Licensing

Every dynamic extension should define the global symbol plugin_is_GPL_compatible to assert that it has been licensed under a GPL-compatible license. If this symbol does not exist, gawk will emit a fatal error and exit.

The declared type of the symbol should be int. It does not need to be in any allocated section, though. The code merely asserts that the symbol exists in the global scope. Something like this is enough:

int plugin_is_GPL_compatible;