linux-kernel - Re: [PATCH] scripts/gdb: replace "is 0" by "== 0"

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Date:   Fri, 20 Mar 2020 16:47:19 +0000
From:   Kieran Bingham <kbingham@...nel.org>
To:     Vincent Bernat <vincent@...nat.ch>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/gdb: replace "is 0" by "== 0"

Hi Vincent,

On 20/03/2020 16:38, Vincent Bernat wrote:
> While for small numbers, using "node is 0" works with CPython, it is
> more portable to use "node == 0". Moreover, with Python 3, this
> triggers a syntax warning:

Oh, I thought python encouraged the 'is' style.

> 
>     SyntaxWarning: "is" with a literal. Did you mean "=="?

Of course that means it clearly doesn't in this case...


> Signed-off-by: Vincent Bernat <vincent@...nat.ch>

Change looks acceptable to me given the report, though a potential
alternative below, otherwise

Reviewed-by: Kieran Bingham <kbingham@...nel.org>

> ---
>  scripts/gdb/linux/rbtree.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/gdb/linux/rbtree.py b/scripts/gdb/linux/rbtree.py
> index 39db889b874c..87d4738984d2 100644
> --- a/scripts/gdb/linux/rbtree.py
> +++ b/scripts/gdb/linux/rbtree.py
> @@ -17,7 +17,7 @@ def rb_first(root):
>          raise gdb.GdbError("Must be struct rb_root not {}".format(root.type))
>  
>      node = root['rb_node']
> -    if node is 0:
> +    if node == 0:

Given the nature of the statement, would

if not node:
    return None

be any more appropriate ?

>          return None
>  
>      while node['rb_left']:
> @@ -33,7 +33,7 @@ def rb_last(root):
>          raise gdb.GdbError("Must be struct rb_root not {}".format(root.type))
>  
>      node = root['rb_node']
> -    if node is 0:
> +    if node == 0:
>          return None
>  
>      while node['rb_right']:
> 


-- 
--
Kieran