Problem with sqlite3_create_function_v2 about jnr-ffi

[pepijnve]

@gwenn I ran into the same problem while trying to convert your sqlite-jna library to jnr. It seems that JNR instantiates a native trampoline and passes a pointer to it on the native function even if the Java callback object is null.
At https://github.com/jnr/jnr-ffi/blob/master/src/main/java/jnr/ffi/provider/jffi/NativeClosureManager.java#L95 I added

if (value == null) {
  return null;
}

at the beginning of ClosureSite#toNative and that seems to resolve the issue.

I haven't found a way to intercept this via the public API so this will have to get fixed in JNR itself. Would be good to get confirmation from one of the JNR maintainers that passing null for callback parameters is indeed not working correctly yet.

[gwenn]

@pepijnve On my side, I fixed the issue with this commit gwenn/sqlite-jna@1593a96
Regards.

[headius]

#77 has been merged, so I believe the next jnr-ffi release will work properly here.

Hoping to wrap up this and other PRs by end of week, so we can put out a 2.0.10 (or 2.1).