Marcin Dalecki wrote:
Wiadomość napisana w dniu 2007-01-24, o godz10:12, przez Michael Veksler:
Andrew, you are both correct and incorrect. Certainly, deterministic
unit testing
is not very useful. However, random unit testing is priceless. I have
been doing
pseudo-random unit tests for years, believe me it makes your code
practically
bug free.
However the problem with applying this kind of methods to GCC would
actually be finding
the units inside the spaghetti. Even a curious look at for example how
-ffast-math works
did give me recently a run from the compiler 'driver' down to the c4x
back-end.
An trivial attempt at doing something about it resulted in a request
for a "full
bootstrap without regressions" for a platform:
This issue of legacy spaghetti is well known and understood. From my
experience,
this can't be fixed in one go. However, it is possible to have a
road-map in which:
1. New code is written in a way that allows random unit testing.
2. Old code is gradually changed.
3. For the time being, integrate unit tests in GCC code (with #ifdef
or some
such).
For example, there will be a code to synthesize some random GIMPLE
or RTL and pass it to an optimization pass. Then some invariants
will be
checked on the resulting GIMPLE/RTL. This is quite complex, but
IMHO doable.
From my experience on my small constraint solver (80,000 LOC) by making
stuff
more suitable for random unit testing you get:
1. Maintainable+reusable code (with all its benefits).
2. Faster code: Due to simplicity of each unit, it is
easier to understand and implement algorithmic enhancements.
If it will involve CP (
http://en.wikipedia.org/wiki/Constraint_programming ) or
CSP solving then there is a slight chance that I will be able to squeeze
some of this
into my schedule of 2008, not before. (I refer only to proof of concept,
at most
a prototype not more).
--
Michael Veksler
http:///tx.technion.ac.il/~mveksler
