linux-kernel - RE: [PATCH] libbpf: Remove unnecessary conversion to bool

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Message-ID: <72757066568b4b64b89572e04d783137@AcuMS.aculab.com>
Date:   Sat, 7 Nov 2020 10:46:14 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Joe Perches' <joe@...ches.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        "xiakaixu1987@...il.com" <xiakaixu1987@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Kaixu Xia <kaixuxia@...cent.com>
Subject: RE: [PATCH] libbpf: Remove unnecessary conversion to bool

From: Joe Perches
> Sent: 06 November 2020 21:50
> 
> On Fri, 2020-11-06 at 13:32 -0800, Andrii Nakryiko wrote:
> > On Thu, Nov 5, 2020 at 11:12 PM <xiakaixu1987@...il.com> wrote:
> > > Fix following warning from coccinelle:
> > > ./tools/lib/bpf/libbpf.c:1478:43-48: WARNING: conversion to bool not needed here
> []
> > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> []
> > > @@ -1475,7 +1475,7 @@ static int set_kcfg_value_tri(struct extern_desc *ext, void *ext_val,
> > >                                 ext->name, value);
> > >                         return -EINVAL;
> > >                 }
> > > -               *(bool *)ext_val = value == 'y' ? true : false;
> > > +               *(bool *)ext_val = value == 'y';
> >
> > I actually did this intentionally. x = y == z; pattern looked too
> > obscure to my taste, tbh.
> 
> It's certainly a question of taste and obviously there is nothing
> wrong with yours.
> 
> Maybe adding parentheses makes the below look less obscure to you?
> 
> 	x = (y == z);

That just leads to people thinking conditionals need to be in parentheses
and then getting the priorities for ?: all wrong as in:
	x = a + (b == c) ? d : e;

It would (probably) be better to make 'ext_val' be a union type
(probably a 'pointer to a union' rather than a union of pointers)
so that all the casts go away.

	David

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