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<div class="moz-cite-prefix">Hi Dmitry!<br>
<br>
Thanks for your interest in GraalVM. Answers are inline below.<br>
<br>
<br>
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<div id="bloop_customfont"
style="font-family:Helvetica,Arial;font-size:16px; color:
rgba(0,0,0,1.0); margin: 0px; line-height: auto;">On 3 May 2018 at
15:40:08, Dmitry Timofeev (<a
href="mailto:dmytro.tymofeev@bitfury.com" moz-do-not-send="true">dmytro.tymofeev@bitfury.com</a>)
wrote:</div>
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<p>Hi,</p>
<p>I’m working on making a framework in a native language
(Rust)
extensible in other languages (Java, Python). We currently
use JNI,
which is low-level and error-prone. I consider if GraalVM
would
make some things easier or make the integration more
efficient.
Would anyone please help with these questions?</p>
<p>1. Is it a good use-case for GraalVM? It seems so from
the docs,
as GraalVM aims to eliminate the costs associated with
calling code
running on a VM from the native code and vice-versa.<br>
</p>
</div>
</div>
</span></blockquote>
Yes, this is a perfect use-case for GraalVM.<br>
<br>
Since Rust compiles to LLVM bitcode, you should be able to run your
Rust code using the LLVM support in GraalVM. But be aware that Rust
support is still experimental. We do most of our testing with C/C++,
only very basic testing is done for Rust, so you'll likely run into
a few bugs, but we're happy to help if you run into problems.<br>
<br>
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cite="mid:etPan.5af2b61a.1ba62c08.6d5@oracle.com"><span>
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<p>
2. The reference documentation says C --> Java is not
supported
yet, but coming soon.</p>
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</span><br>
<span></span></blockquote>
Support for C->Java interop (actually LLVM->Java interop) just
landed in master (see
<a class="moz-txt-link-freetext" href="https://github.com/graalvm/sulong/commit/a8ec4a7e8cb4488c7f8b774bbc7b1342efd92c71">https://github.com/graalvm/sulong/commit/a8ec4a7e8cb4488c7f8b774bbc7b1342efd92c71</a>
), and will be included in RC2.<br>
<br>
<blockquote type="cite"
cite="mid:etPan.5af2b61a.1ba62c08.6d5@oracle.com"><span>
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<p> Does it mean that developers will be able to
use Java from C with <i>no</i> JNI (= pass arbitrary
structs, call
any Java method from any native thread)? Is it going to be
a viable
full-featured replacement for any JNI use-case?</p>
</div>
</div>
</span><br>
<span></span></blockquote>
Note that our LLVM->Java interface is different from usual native
interfaces, since running LLVM code in GraalVM is not actually
running native code, it is running the LLVM code inside the managed
VM (but still accessing native memory). Because of that, it's not
directly comparable to JNI. With JNI, you're basically "leaving" the
VM when you call a native method. With LLVM on GraalVM, you're
running your C/C++/Rust code inside the VM.<br>
<br>
The LLVM->Java interface is very similar to all other LLVM->*
interop interfaces we have in GraalVM (see
<a class="moz-txt-link-freetext" href="http://www.graalvm.org/docs/reference-manual/languages/llvm/#interoperability">http://www.graalvm.org/docs/reference-manual/languages/llvm/#interoperability</a>
and <a class="moz-txt-link-freetext" href="http://www.graalvm.org/docs/reference-manual/polyglot/">http://www.graalvm.org/docs/reference-manual/polyglot/</a>).<br>
You can just load Java classes and use them using the regular
polyglot builtin functions. You can pass native structs and access
them from Java directly, and you can "cast" Java objects to native
structs and access them as if they were real native memory. All of
this works without any data copying. This is one of the main
advantages of our polyglot execution model. And all of that works
not just with Java objects, but also with all other languages that
run on GraalVM (e.g. Javascript). As such, this is much more
flexible than JNI.<br>
<br>
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cite="mid:etPan.5af2b61a.1ba62c08.6d5@oracle.com"><span>
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<p>
3. If I do such integration of a native language with Java
the old
way — using JNI, native methods and libraries — but run on
GraalVM,
will this application enjoy any inter-language
optimizations?</p>
</div>
</div>
</span><br>
<span></span></blockquote>
No, the compiler can not optimize across JNI calls. You will of
course still get all optimizations between the individual GraalVM
languages when they call each other and exchange data, but every
transition from/to native code will be an optimization boundary for
the compiler.<br>
<br>
<br>
I hope this answers your questions. Your project sounds very
interesting, I encourage you to play around with that, and report
any problems you encounter.<br>
<br>
- Roland<br>
<br>
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<p>Thanks!<br>
</p>
<pre class="moz-signature" cols="72">--
Dmitry
</pre>
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