Re: stable plugin introspection API ... Where?

[Richard Biener <richard dot guenther at gmail dot com>]

On Sun, Feb 14, 2016 at 3:50 PM, Basile Starynkevitch
<basile@starynkevitch.net> wrote:
> Dear all
>
> In https://gcc.gnu.org/ml/gcc/2016-02/msg00157.html
>
> Richard Biener (richard dot guenther at gmail dot com) is mentioning:
>
>> Help with picking up the partially completed work on a stable plugin
>> (introspection) API is of course welcome.
>
>
>
> Can anyone explain me what and where is that stable plugin introspection
> API?

It's a proposal, follow the thread here (also up-thread).  There were similar
threads with another (python?) plugin API from David Malcom(?) IIRC.

https://gcc.gnu.org/ml/gcc/2012-09/msg00098.html

> In https://gcc.gnu.org/ml/gcc/2016-02/msg00159.html I (Basile) wrote:
>
>> What exact functions (their name, the source files defining them) in the
>> current GCC trunk
>> are you referring to by your "introspection" word? Last time I checked (a
>> few months ago)
>> there where nothing related to that. Today, the only occurrences of
>> introspection
>> (in GCC trunk svn rev233268) are in Java part and in the libsanitizer.
>
> FWIW, Richard Beiner did not had time or wish to answer to that
> (I've got no answer neither privately nor on the list).
>
> So I am rephrasing my question:
>
> which functions and source files are relevant today in the trunk for a
> "stable plugin introspection API"?

None, it doesn't exist in trunk (nor does Melt exist in trunk).

>
>
> I did try to find something related, but my search is completely
> unsuccessful yet.
>
> My feeling (and I really hope to be wrong, because any reflective or
> introspective
> ability in GCC would help my work in the MELT plugin, see
> http://gcc-melt.org/ for more, a big lot)
> is that today there is no plugin-related introspection API at all in GCC. It
> still
> looks today (february 20165) as a wish or some vaporware.

Correct.  It has to be filled with reality from plugin people.  I personally
care zero for plugins but will of course guard what gets into the GCC repository
itself (a thin translation layer from GCC internals to a "plugin API",
avoiding the
need to export all of GCCs internals as "API").

> I still hope to be very wrong, but then please enlighten me by naming the
> actual functions and source files
> related to the plugin introspection API. Or give me some source files and
> line numbers
> (in the GCC trunk, i.e. future GCC 6,  of february 2016) if you like so.
>
>
> Since I am not a native English speaker, I am referring to:
>
> https://en.wikipedia.org/wiki/Type_introspection
> https://en.wikipedia.org/wiki/Reflection_%28computer_programming%29
> https://en.wikipedia.org/wiki/Homoiconicity
> https://en.wikipedia.org/wiki/Metadata
> https://en.wikipedia.org/wiki/Metaclass
>
> (BTW, MELT does have some of these, but they are currently for MELT specific
> features,
>  not yet for general GCC ones; this means that I -Basile- value & cherish
> these features
> a lot and I am hungry
> to have them inside GCC)

I proposed to define a stable introspection API because a) people like the
idea of a stable plugin API (or even ABI!), b) introspection is easy - no
code modification, only inspection, but also enough for a variety of
academic uses, c) introspection can be reasonably defined compiler-independent
and thus plugin sharing between, say, GCC and LLVM should be possible

Step 2 would be to add basic instrumentation support to the API
(add global data, insert calls or simple statements at program points).

I wouldn't ever go as far as allowing arbitrary IL modification in a stable
API as that's not going to work and I believe in "real passes" living
in GCC itself.

To sum up:  if you like your issues resolved help driving that tiny abstraction
layer.

Richard.

> So it looks like Richard see a "partially completed work" on "plugin
> introspection API"
> while I (Basile) don't see even the smallest start about it (or even
> consensus about wishing that).
> I hope to be wrong, so please point me some actual piece of code related to
> that in GCC 6.
>
> FWIW, it is possible for some C++ program to have some metadata. Qt is a
> concrete example.
> http://doc.qt.io/qt-5/metaobjects.html;
> GTK is explicitly mentioning Introspection in
> https://wiki.gnome.org/Projects/GObjectIntrospection
> but I don't see anything remotely related to such things inside GCC.
>
> AFAIU, we don't have any programmatic way to query the GCC API useful in
> plugins today.
>
> So please help me finding some related features in current GCC 6 (trunk)
> code base (in February 2016).
>
> I'm sure that most plugin writers would be pleased to know about that.
>
> Regards.
>
>
> --
> Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
> email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
> 8, rue de la Faiencerie, 92340 Bourg La Reine, France
> *** opinions {are only mine, sont seulement les miennes} ***
>