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

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Message-ID: <b8a2b88e484cac27a82e1c27d0e27599515c4bc6.camel@redhat.com>
Date: Tue, 20 Jan 2026 09:59:11 +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 Mon, 2026-01-19 at 17:45 -0300, Wander Lairson Costa wrote:
> Initialize loop variable `i` before the for loop in abbreviate_atoms
> function to fix pyright static type checker error. The previous code
> left `i` potentially unbound in edge cases where the range could be
> empty, though this would not occur in practice since the loop always
> executes at least once with the given range parameters.
> 
> The initialization to zero ensures that `i` has a defined value before
> entering the loop scope, satisfying static analysis requirements
> while preserving the existing logic. The for loop immediately assigns
> i to the first value from the range, so the initialization value is
> never actually used in normal execution paths.
> 
> This change resolves the pyright reportPossiblyUnbound error without
> altering the function's behavior or performance characteristics.

So are we just pleasing the tool or is there a real implication of this?

Apparently code like

for i in range(len([]), -1, -1):
    pass
print(i)

works just fine since range() returns at least 0 (as you mentioned in the commit
message) and i is not used before assignation in the loop, so I don't really see
a problem.

Apparently pyright devs don't want ([1]) to implement a logic to sort out the
/possibly/ unbound error here.

>From what I understand, this code is already not pythonic, so rather than
silence the warning to please this tool I'd just refactor the code not to use i
after the loop (or leave it as it is, since it works fine).

What do you think?

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