linux-kernel - Re: [PATCH] Bluetooth: Pre-initialize variables in read_local_oob_ext_data

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Message-Id: <8684664B-22C2-45E8-B547-48F173B3CA7A@holtmann.org>
Date:	Fri, 17 Apr 2015 13:38:47 -0700
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	"Gustavo F. Padovan" <gustavo@...ovan.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	BlueZ development <linux-bluetooth@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Bluetooth: Pre-initialize variables in read_local_oob_ext_data_complete()

Hi Geert,

>>> net/bluetooth/mgmt.c: In function ‘read_local_oob_ext_data_complete’:
>>> net/bluetooth/mgmt.c:6474: warning: ‘r256’ may be used uninitialized in this function
>>> net/bluetooth/mgmt.c:6474: warning: ‘h256’ may be used uninitialized in this function
>>> net/bluetooth/mgmt.c:6474: warning: ‘r192’ may be used uninitialized in this function
>>> net/bluetooth/mgmt.c:6474: warning: ‘h192’ may be used uninitialized in this function
>>> 
>>> While these are false positives, the code can be shortened by
>>> pre-initializing the hash table pointers and eir_len. This has the side
>>> effect of killing the compiler warnings.
>> 
>> can you be a bit specific on which compiler version is this. I fixed one occurrence that seemed valid. However in this case the compiler seems to be just plain stupid. On a gcc 4.9, I am not seeing these for example.
> 
> gcc 4.1.2. As there were too many false positives, these warnings were
> disabled in later versions (throwing away the children with the bad water).
> 
> If you don't like my patch, just drop it. I only look at newly
> introduced warnings
> of this kind anyway.

I really do not know what is the best solution here. This is a false positive. And I have been looking at this particular code for a warning that was valid, but we missed initially. But these warnings that you are fixing are clearly false positive.

If this only happens with an old compiler version, I would tend to leave the code as is. Then again, what is the general preferred approach here?

Regards

Marcel

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