Re: MELT tutorial on the wiki

[Basile STARYNKEVITCH <basile at starynkevitch dot net>]

Paolo Bonzini wrote:
> > For example, gdb has function that in the past could return null, but
> > which now cannot.  So, I'd like to find all places where the return
> > result is checked.
> >
> > Or, gdb has a TRY_CATCH macro which expands to a couple of nested loops.
> > It is not ok to 'return' or 'goto' from inside the inner loop, as this
> > causes hard-to-find bugs.  So, it would be nice to find any place that
> > tries this.
> >
> > Or, there is a data type in gdb that used to be freed using 'xfree', but
> > which now requires a special function to be called instead.  So, it
> > would be nice to find any place where xfree is passed an argument of
> > this type.
>
> MELT looks extremely cool!  You may want to use this too, however:
>
> http://lwn.net/Articles/315686/

This is about Coccinelle so http://coccinelle.lip6.fr/ is a better link.

Indeed, Tom Tromey might also try Coccinelle. However, MELT is a 
different beast: above all, it is tightly integrated inside GCC, and is 
designed & useful to write (or at least prototype) GCC passes (mostly in 
the middle end); while Coccinnelle is a tool unrelated to GCC (except 
for the input language, i.e. C).

Since MELT works on GCC internal representations, it should be able to 
deal with all the source languages GCC is able to compile.

So I would say that MELT is complementary to Coccinelle.

BTW, people interested in static analysis for C (not C++ or Ada) might 
look at FramaC http://frama-c.cea.fr/ which is unrelated to GCC (except 
for its use of the preprocessor).


I believe MELT could be best viewed as a tool for GCC plugins, either 
"analysis" plugins -which don't change the code and don't influence the 
GCC generated object code, or "transformation" or "optimisation" 
plugins, which do change the GCC code generation.

For people able to review patches, my most desirable patch is
http://gcc.gnu.org/ml/gcc-patches/2009-07/msg00507.html (a patch for 
gengtype). Currently, MELT can be compiled as a plugin to an unmodified 
GCC-trunk (ie 4.5) binary, but to compile MELT you need this patch 
(which improves the C code generated by gengtype in plugin mode).

Regards.


PS. In a few days, I'm leaving on vacation for almost 3 weeks without 
email access.

--
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
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