Re: Proposed plugin API for GCC

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

On Thu, Mar 29, 2012 at 10:58 PM, David Malcolm <dmalcolm@redhat.com> wrote:
> I had a go at writing a possible plugin API for GCC, and porting parts
> of my python plugin to it:
> http://git.fedorahosted.org/git/?p=gcc-python-plugin.git;a=commitdiff;h=36a0d6a45473c39db550915f8419a794f2f5653e
>
> It's very much at the "crude early prototype" stage - all I've wrapped
> is part of CFG-handling - but the important thing is that python plugin
> *does* actually compile against this, and many of its selftests still
> pass (though I'm breaking the self-imposed encapsulation in quite a few
> places in order to get it to compile).
>
> The code is currently jointly owned by me and Red Hat; I'm sure we can
> do copyright assignment if/when it comes to that.
>
> You can see the work-in-progress in the "proposed-plugin-api" branch of
> gcc-python-plugin.
>
> For example, the proposed public header file looks like this:
> http://git.fedorahosted.org/git/?p=gcc-python-plugin.git;a=blob;f=proposed-plugin-api/gcc-cfg.h;h=8dbeed0a6c5eb14b0336e89493746887c3bec20a;hb=36a0d6a45473c39db550915f8419a794f2f5653e
>
> For example, some design notes can be seen at:
> http://git.fedorahosted.org/git/?p=gcc-python-plugin.git;a=blob;f=proposed-plugin-api/design.rst;h=31b960ccac2dcf4d007701b5e9c6556e68e0d107;hb=36a0d6a45473c39db550915f8419a794f2f5653e
>
> How do other plugin authors feel about the API?

Of course I don't like the CamelCasing ;)

The important part of the API is that it exposes no data structures and
all object references we expose are opaque.

You have mostly wrapped in an iterator-style way, I suppose that's fine.
That (and the CamelCasing) exposes that using a different language for
this API would be desired; use namespaces to avoid CamelCasing and
STL style iterators / functors for the rest.  If you stay with C rather
than using callbacks I would use an explicit iterator representation,
similar to how we have that now with gimple_stmt_iterator.  Of course
that's personal preference, subject to bikeshedding.

Would the python plugin have any issue with using C++?

> How do GCC subsystem maintainers feel?

Well, positive!  Thanks for starting.  CFG introspection is indeed one
of the most important parts, then callgraph and statement introspection.

> I initially attempted an underscore_based_naming_convention but quickly
> found it difficult to get concise function names, so I switched to a
> CamelCaseBased_NamingConvention with an underscore separating a notional
> namespace element from a secondary element, which saved plenty of space.
> The different naming convention also serves to highlight that this is
> *not* part of GCC's internals.
>
> Hope this is constructive

Indeed, and thank you for that.

Btw, how ugly is it to make this API grokable by swig?  Would that serve
the python plugin?

Thanks,
Richard.