File: gawk.info,  Node: Plugin License,  Next: Extension Mechanism Outline,  Prev: Extension Intro,  Up: Dynamic Extensions

17.2 Extension Licensing
========================

Every dynamic extension must be distributed under a license that is
compatible with the GNU GPL (*note Copying::).

   In order for the extension to tell 'gawk' that it is properly
licensed, the extension must define the global symbol
'plugin_is_GPL_compatible'.  If this symbol does not exist, 'gawk' emits
a fatal error and exits when it tries to load your extension.

   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;