linux-kernel - Compiler warning about comparing result of !!test

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Message-ID: <8828.1430144003@warthog.procyon.org.uk>
Date:	Mon, 27 Apr 2015 15:13:23 +0100
From:	David Howells <dhowells@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org
Subject: Compiler warning about comparing result of !!test_bit() to an integer

Hi Jiri,

This line in hid-input.c:

	if (usage->type == EV_KEY && !!test_bit(usage->code, input->key) != value)
		input_event(input, EV_MSC, MSC_SCAN, usage->hid);

gives:

../drivers/hid/hid-input.c: In function 'hidinput_hid_event':
../drivers/hid/hid-input.c:1160:167: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]

with gcc-5.1.  Given that 'value' doesn't appear to be a boolean, is this correct?

This was introduced by commit c01d50d181f074a60bf3ed54eb055ce1679afb98.

David
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