linux-kernel - Re: [PATCH] befs/btree: remove unneeded initializations

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Message-ID: <574F7317.3030802@osg.samsung.com>
Date:	Thu, 02 Jun 2016 00:43:19 +0100
From:	Luis de Bethencourt <luisbg@....samsung.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	fabf@...net.be
Subject: Re: [PATCH] befs/btree: remove unneeded initializations

On 01/06/16 23:42, Andrew Morton wrote:
> On Mon, 30 May 2016 01:39:59 +0100 Luis de Bethencourt <luisbg@....samsung.com> wrote:
> 
>> off in befs_bt_read_node() will be written by befs_read_datastream(), with
>> the value that node->od_node needs.
>>
>> node_off in befs_btree_read() isn't read before set to root_node_ptr.
>>
>> Removing these two unneeded initializations.
>>
>> ...
>>
>> --- a/fs/befs/btree.c
>> +++ b/fs/befs/btree.c
>> @@ -196,7 +196,7 @@ static int
>>  befs_bt_read_node(struct super_block *sb, const befs_data_stream *ds,
>>  		  struct befs_btree_node *node, befs_off_t node_off)
>>  {
>> -	uint off = 0;
>> +	uint off;
>>  
>>  	befs_debug(sb, "---> %s", __func__);
>>  
> 
> With this code:
> 
> 	int foo;
> 
> 	bar(&foo);
> 
> 	whatever = foo;
> 
> some versions of gcc will warn that foo might be used uninitialized. 
> Other versions of gcc don't do this.  That's why the seemingly-unneeded
> initializations are there.
> 
> Neither of the versions of gcc which I tested with actually do warn,
> but I'm inclined to leave things as-is: some people will get warnings
> and that's probably worse than a couple of bytes bloat in befs.
> 
> It shouldn't cause any bloat, really.  We have the "uninitialized_var"
> macro which avoids any bloat and is self-documenting.  And the nice
> thing about self-documenting code is that it prevents Andrew from
> having to explain strange code to Luis ;)  But unintialized_var in
> unpopular for reasons which I personally find unpersuasive, given
> the advantages...
> 

I understand. Let's keep the code as it is.

Not worth adding uninitialized_var() for that declaration. Even though they
are self-documenting indeed.

Is this also the case with the node_off declaration?
Before being passed by reference to befs_btree_seekleaf() the initial value
is overwritten with node_off = bt_super.root_node_ptr;

Thanks for reviewing this,
Luis