<div style="font-family: Arial, sans-serif; font-size: 14px;"></div><span>dynamic dispatch</span><div><span><br></span></div><div><span>I tried following example [<a target="_blank" rel="noreferrer nofollow noopener" href="https://github.com/enatai/panamaexperiments/blob/main/libcppexperiments/src/main/public/happy.hpp">https://github.com/enatai/panamaexperiments/blob/main/libcppexperiments/src/main/public/happy.hpp</a>] and it works fine as long as we generate proper Java bindings.</span></div><div><br></div><div><span>See test for it [<a target="_blank" rel="noreferrer nofollow noopener" href="https://github.com/enatai/panamaexperiments/blob/main/cppexperiments/src/test/java/cppexperiments/HappyTests.java#L36">https://github.com/enatai/panamaexperiments/blob/main/cppexperiments/src/test/java/cppexperiments/HappyTests.java#L36</a>]</span></div><div><br></div><div><span>Please let me know which dynamic dispatch use cases you are concerned with. Because this one seems works fine.</span></div><div><br></div><div><span>std::string</span></div><div><span>I totally forgot that such basic type like std::string in C++ is a template. </span></div><div><span>But it seems possible to call functions which operate with string objects because symbols for them are present:</span></div><div><br></div><div><span>00000000000013ad T _ZN7unhappy10helloWorldB5cxx11Ev</span></div><div><br></div><div><span>std::string helloWorld();</span></div><div><br></div><div><span>I guess it is possible to create/extract layout for std::string using FFM but:</span></div><div><span>- how to initialize this layout from Java? we cannot just call std::string constructor for it, right?</span></div><div><span>- this layout may differ between different C++ runtimes (libstdc++ etc). MS C++ may have not same std::string layout as GCC</span></div><div><br></div><div><span>> Their binding generator adopts the same simple approach as the one I showed in the patch.</span></div><div><br></div><div><span>I will take a look</span></div><div><br></div><span></span><div style="font-family: Arial, sans-serif; font-size: 14px;"><br></div><div class="protonmail_quote">
------- Original Message -------<br>
On Tuesday, May 23rd, 2023 at 8:58 AM, Maurizio Cimadamore <maurizio.cimadamore@oracle.com> wrote:<br><br>
<blockquote class="protonmail_quote" type="cite">
<p><br>
</p>
<div class="moz-cite-prefix">On 23/05/2023 05:11, Rel wrote:<br>
</div>
<blockquote type="cite">
<span>> What I meant for "robust analysis" was to try and
establish how many _real-world_ C++ library can really be
tackled in such a direct approach. </span>
<div><br>
</div>
<div><span>Ohh I see now, I am affraid we know the answer for this
:)</span></div>
<div><br>
</div>
<div><span>Let's imagine if number of C++ libraries which can be
covered end-to-end with "simple" approach is 0, does it mean
that we should discard it and only focus on shim for binding
all kinds of APIs? What about those cases which can be easily
extracted using "simple" approach, like Point2d?</span></div>
</blockquote>
Perhaps we should reach out to the Rust community? Their binding
generator adopts the same simple approach as the one I showed in the
patch. Given how hard it is to support C++ (because the underlying
libclang C API is not very solid in that respect), I'd be surprised
if they maintained all the necessary code just for stuff like
Point2d?<br>
<blockquote type="cite">
<div><br>
</div>
<div><span>Because I thought that we would like to do "analysis"
of what C++ use cases can/cannot be covered with "simple"
approach. For example from your previous message I see that we
are not completely sure about exceptions:</span></div>
<div><br>
</div>
<div><span>> * (probably way more stuff, like exceptions, etc.)</span></div>
<div><br>
</div>
<div><span>Similarly for myself I would like to see what are the
problems with "dynamic dispatch". I added it to "unhappy" for
now, because we expect it not to work, but I plan to test it
to see what are the issues there and share here. Similarly
with that anyone would be able to reproduce and see same
results.</span></div>
<div><br>
</div>
<div><span>I guess my question now is: do we think it may be
useful to know exactly how many C++ use cases can be covered
with "simple" FFM approach. And if answer is yes, then we can
use panamaexperiments as a playground where we can have tests
for what is covered. This (possibly?) can give us more
confidence in limitations of "simple" approach and how far we
can go with it (and this can be easily demonstrated to
everyone just by running those tests)<br>
</span></div>
</blockquote>
<p>I think it would be useful to know some answer to that question,
yes. My intuition tells me that there are probably two kinds of
C++ libraries: those who were born that way, and those that moved
over from being simpler C libraries. One such example in the
latter category is OpenCV [1]. While its "core" header [2]
declares an exception, as well as a bunch of classes, eyeballing
it, it doesn't seem "too" problematic? Perhaps that would be a
good point where to start, and, if a library such as that can be
used with some degree of success, perhaps we can expand the search
to other similar libraries.</p>
<p>[1] - <a href="https://opencv.org/" class="moz-txt-link-freetext" rel="noreferrer nofollow noopener" target="_blank">https://opencv.org/</a><br>
[2] -
<a href="https://github.com/opencv/opencv/blob/4.x/modules/core/include/opencv2/core.hpp" class="moz-txt-link-freetext" rel="noreferrer nofollow noopener" target="_blank">https://github.com/opencv/opencv/blob/4.x/modules/core/include/opencv2/core.hpp</a><br>
</p>
<blockquote type="cite">
<div style="font-family: Arial, sans-serif; font-size: 14px;
color: rgb(0, 0, 0);"><br>
</div>
<div style="font-family: Arial, sans-serif; font-size: 14px;
color: rgb(0, 0, 0);">Ideas?<br>
</div>
<span></span>
<div style="font-family: Arial, sans-serif; font-size: 14px;"><br>
</div>
<div class="protonmail_quote"> ------- Original Message -------<br>
On Monday, May 22nd, 2023 at 9:14 AM, Maurizio Cimadamore
<a href="mailto:maurizio.cimadamore@oracle.com" class="moz-txt-link-rfc2396E" rel="noreferrer nofollow noopener" target="_blank"><maurizio.cimadamore@oracle.com></a> wrote:<br>
<br>
<blockquote type="cite" class="protonmail_quote">
<p><br>
</p>
<div class="moz-cite-prefix">On 22/05/2023 04:12, Rel wrote:<br>
</div>
<blockquote type="cite">
<blockquote type="cite" style="color: #8c8c8c;">
<pre class="moz-quote-pre">But I believe some more robust
analysis should be made to understand exactly how many APIs can be
supported in this "simple" fashion.
</pre>
</blockquote>
<pre class="moz-quote-pre">Yes, I started to gather such analysis here <a target="_blank" rel="noreferrer nofollow noopener" class="moz-txt-link-freetext" href="https://urldefense.com/v3/__https://github.com/enatai/panamaexperiments__;!!ACWV5N9M2RV99hQ!KOxdK2qmmSzlaaO3kSlSUG2-ifWAVRD6OHlz9NHYvuggmy7NnnNxWvHYcxDm0Vn4gPXlbasjfC-ehIx_KlWNYiU$">https://urldefense.com/v3/__https://github.com/enatai/panamaexperiments__;!!ACWV5N9M2RV99hQ!KOxdK2qmmSzlaaO3kSlSUG2-ifWAVRD6OHlz9NHYvuggmy7NnnNxWvHYcxDm0Vn4gPXlbasjfC-ehIx_KlWNYiU$</a>
Currently there is only one happy case [<a target="_blank" rel="noreferrer nofollow noopener" class="moz-txt-link-freetext" href="https://urldefense.com/v3/__https://github.com/enatai/panamaexperiments/blob/main/libcppexperiments/src/main/public/happy.hpp__;!!ACWV5N9M2RV99hQ!KOxdK2qmmSzlaaO3kSlSUG2-ifWAVRD6OHlz9NHYvuggmy7NnnNxWvHYcxDm0Vn4gPXlbasjfC-ehIx_K7Nl50c$">https://urldefense.com/v3/__https://github.com/enatai/panamaexperiments/blob/main/libcppexperiments/src/main/public/happy.hpp__;!!ACWV5N9M2RV99hQ!KOxdK2qmmSzlaaO3kSlSUG2-ifWAVRD6OHlz9NHYvuggmy7NnnNxWvHYcxDm0Vn4gPXlbasjfC-ehIx_K7Nl50c$</a> ] which is Point2d class from your foo.hpp file.</pre>
</blockquote>
<p>This is not too surprising - after all the hacky changes I
shared were built around that example.</p>
<p>What I meant for "robust analysis" was to try and establish
how many _real-world_ C++ library can really be tackled in
such a direct approach. My feeling is "not many" - but I
don't have any hard data to back up this claim.</p>
<p>Maurizio<br>
</p>
</blockquote>
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