[Openmcl-devel] Static Program Analysis

[Gary Byers]

One of the reasons why tools like this don't exist (or don't exist in
great number) is they'r hard to write, both in the sense of being
tricky, non-trivial pieces of code and because CL doesn't provide
portable means to do the kind of code-walking that CL compilers may do
in an ad hoc, probably non-extensible way.

An X3J13 proposal to provide some of that support - I think that
it was called SYNTACTIC-ENVIRONMENT-ACCESS - was once passed,
and the facilities it offered were describe in CLtL2.  There were
some design problems with the original proposal: a function called
DEFINE-DECLARATION either couldn't have worked or wouldn't have
been particularly as part of the basis for a general-purpose
code-walker or similar tools.  (It's been a long time, and I
don't remember the issues clearly.)

PCL ("Portable Common Loops", a portable CLOS implementation)
used a code-walker to determine things like whether a method
body contained apparent calls to CALL-NEXT-METHOD and likely
a few other things.  (It'd be interesting to know whether
a variable bound to a specialized method parameter is ever
SETQed, since some optimizations may be possible if the
class of an object is known at compile-time and determining
the class of a variable bound to a parameter is easier if
you don't have to worry about SETQ.)

Franz gave a presentation at ILC 2 years ago in which they
suggested semi-standard adoptation of a framework that they
use.  My impression at the time was that it was similar to
the old SYNTACTC-ENVIRONMENT-ACCESS proposal with some of
the problems addressed and some holes filled.  (I may be
mis-characterizing it, and have been meaning to think 
harder about it than I have over the last couple of years.)

The natural, lisp-y way of looking at some of this is to
say "If I just had an industrial strength code-walker, I
could use that tool to build other tools that perform
compiler-like analysis."  People have had some difficulty
defining exactly what tools an implementation should offer
in order to make the development of a portable code-walker
easier, and the closest thing to a "portable code-walker"
that I know of is probably PCL's.  (PCL's code-walker
defined a high-level interface, implemented in large chunks
of implementation-specific code.  It worked in MCL 20 years
ago, but the last time anyone tried to get it working in
OpenMCL is was obvious that bitrot had set in.)

I'm a little more interested in the approach of (for instance)
reviving/productizing/conditionalizing the PCL walker than
I am in trying to standardize on a portable layer underneath
that.

On Thu, 11 Jan 2007, Brent Fulgham wrote:

> If I remember correctly, Stalin is a Scheme compiler -- so it falls into the CMUCL/SBCL optimization camp.
>
> I'm curious if any tools exist to perform analysis on Lisp code so that a user could the review the program to deal with specific coding errors.
>
> ----- Original Message ----
> From: Hamilton Link <helink at sandia.gov>
> To: Brent Fulgham <bfulg at pacbell.net>; openmcl-devel <openmcl-devel at clozure.com>
> Sent: Thursday, January 11, 2007 1:27:05 PM
> Subject: Re: [Openmcl-devel] Static Program Analysis
>
> I don't know about lisp, but there are such things for scheme... Stalin
> is one that springs to mind, if I am recalling correctly what it does.
> h
>
> Brent Fulgham wrote:
>> I was reading that the Common Lisp standard supports various type declarations that may be used by the compiler to perform some optimizations.  I also know I've seen various messages from the OpenMCL compiler that it performs some type of analysis, since it identifies unreferenced variables, undeclared functions, etc.
>>
>> I'm curious if any tools exist in Common Lisp (or perhaps are already part of the compiler) that perform static analysis, along the lines of the Erlang Dialyzer (http://www.it.uu.se/research/group/hipe/dialyzer/) or even DrScheme's MrSpidey (http://www.cs.brown.edu/~sk/Publications/Papers/Published/ffkwf-mrspidey/).
>>
>> These tools can identify cases where a user attempts to execute non-functions, perform math on non-numbers, etc.
>>
>> The only thing a Google search turned up for me was an ancient (circa mid-80's) reference to an internal HP project called "MicroScope".  I don't see much else that is more recent.  The concensus on the #lisp IRC channel was that some static analysis is done in SBCL/CMUCL, but no one knew of any external tools.
>>
>> Thanks,
>>
>> -Brent
>>
>>
>>
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