"introduce no new bootstrap warning" criteria. was: Loop iv debugging, patch

[Kaveh R. Ghazi]

 > From: Geoff Keating <geoffk@geoffk.org>
 > 
 > There's a big gotcha here: the regression tester uses gcc 2.95.2 as
 > the host compiler.  Thus, it gets quite a number of spurious
 > warnings due to bugs in 2.95.2.

So we'd have to run a separate build for the warning regression
checker and use a relatively recent CVS gcc to generate the warnings.


 >   It's also not reproducible,
 > because the warnings you get on sparc-solaris are not the same set
 > as the warnings you get on x86-linux or even sparc-linux.  This is
 > likely to be a fatal problem for any such tool.

I think what you mean here is that once the checker finds a
regression, the person who caused it may not be able to reproduce it
on their host platforms.  That's quite possible, but having the
checker is better then not having it.  I think if we run the checker
native on x86-linux-gnu, we start with a common enough platform that
most developers have access to.  If someone working elsewhere
introduces a warning only seen on x86-linux-gnu, they may still be
able to fix it because most warnings are obvious by inspection.  Still
we'll have to work out how to fix it some other way via a volunteer if
the original culprit can't do so.  I don't think this is fatal.


 > IMO, it would be better to switch off -Wall, switch on -Werror, and
 > switch on individual warning flags until something breaks.
 > - Geoffrey Keating <geoffk@geoffk.org>

I'm not sure if you mean to do this for all bootstraps or just the
warning checker host.

If done for everyone, you'd still run into the problems I outlined in
my previous message about unfixable warnings.  If done only for the
checker system, unless you fix every remaining warning you'd have so
few -W* flags turned on that the inactive ones (e.g. -Wsign-compare)
will regress very quickly since no one sees them any more.

IMHO, we could get a regression checker up relatively quickly, but
getting -Werror working is far away.  I'm willing to be proven false
by a working example though. :-)

		--Kaveh
--
Kaveh R. Ghazi			Engagement Manager / Project Services
ghazi@caip.rutgers.edu		Qwest Internet Solutions