linux-kernel - Re: [PATCH 17/26] rv/rvgen: fix possibly unbound variable in ltl2k

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Message-ID: <7e83ab8b607cdc9e1c677e7b118d46eabe35b7f8.camel@redhat.com>
Date: Wed, 21 Jan 2026 07:31:22 +0100
From: Gabriele Monaco <gmonaco@...hat.com>
To: Wander Lairson Costa <wander@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Nam Cao <namcao@...utronix.de>, 
 open list <linux-kernel@...r.kernel.org>, "open list:RUNTIME VERIFICATION
 (RV)"	 <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH 17/26] rv/rvgen: fix possibly unbound variable in ltl2k

On Tue, 2026-01-20 at 16:38 -0300, Wander Lairson Costa wrote:
> On Tue, Jan 20, 2026 at 01:30:35PM +0100, Gabriele Monaco wrote:
> 
> > You basically want i to be the length of the longest prefix common to at
> > least
> > another atom.
> > 
> > You could assign i to some python trick doing the exact same thing the loop
> > does, like:
> > 
> >     i = next((i for i in range(len(atom), -1, -1)
> >         if sum(a.startswith(atom[:i]) for a in atoms) > 1))
> > 
> > next() is basically doing the break at the first occurrence from the
> > generator,
> > just now your i doesn't live (only) inside the loop.
> > 
> > So now you save 2 lines and get any C developer scratch their head when they
> > look at the code, but hey, pyright is happy!
> > 
> 
> Or just leave the assignment.
> 
> > If you do find the trick with next() readable or have any better idea, feel
> > free
> > to try though.
> > 
> 
> Definitely the next() trick is not worth to make pyright happy.

Alright, thinking on this again next() is the python way to do if(...) break ,
it looked a bit odd to me only because I didn't know about it, but if you're
using python iterators, it kinda makes sense.

Anyway I'm fine also with the dull assignment, there's no need to argue on this.

Thanks,
Gabriele

> 
> > Thanks,
> > Gabriele
> > 
> > > I will modify it in v2.
> > > 
> > > > 
> > > > Thanks,
> > > > Gabriele
> > > > 
> > > > [1] - https://github.com/microsoft/pyright/issues/844
> > > > 
> > > > > 
> > > > > Signed-off-by: Wander Lairson Costa <wander@...hat.com>
> > > > > ---
> > > > >  tools/verification/rvgen/rvgen/ltl2k.py | 1 +
> > > > >  1 file changed, 1 insertion(+)
> > > > > 
> > > > > diff --git a/tools/verification/rvgen/rvgen/ltl2k.py
> > > > > b/tools/verification/rvgen/rvgen/ltl2k.py
> > > > > index fa9ea6d597095..94dc64af1716d 100644
> > > > > --- a/tools/verification/rvgen/rvgen/ltl2k.py
> > > > > +++ b/tools/verification/rvgen/rvgen/ltl2k.py
> > > > > @@ -45,6 +45,7 @@ def abbreviate_atoms(atoms: list[str]) -> list[str]:
> > > > >  
> > > > >      abbrs = []
> > > > >      for atom in atoms:
> > > > > +        i = 0
> > > > >          for i in range(len(atom), -1, -1):
> > > > >              if sum(a.startswith(atom[:i]) for a in atoms) > 1:
> > > > >                  break
> > > > 
> >