c_g_cclosure_marshal_VOID__DOUBLE

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
__gshared extern (C)
void function(GClosure* closure, GValue* returnValue, guint nParamValues, GValue* paramValues, void* invocationHint, void* marshalData) c_g_cclosure_marshal_VOID__DOUBLE;

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