linux-ext4 - Re: [PATCH 1/7] ext4: Introduce le32_t and le16

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Date:	Tue, 25 Sep 2007 16:02:23 +0000
From:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org, adilger@...sterfs.com, cmm@...ibm.com
Subject: Re: [PATCH 1/7] ext4: Introduce le32_t and le16_t

On Tue, 2007-09-25 at 21:15 +0530, Aneesh Kumar K.V wrote:
> 
> Dave Kleikamp wrote:
> > On Tue, 2007-09-25 at 14:33 +0530, Aneesh Kumar K.V wrote:
> >> ext4 file system layout contain different split members
> >> like bg_block_bitmap  and bg_block_bitmap_hi. Introduce
> >> data type le32_t and le16_t to be used as the type of
> >> these split members. This prevents these members frome
> >> being accessed directly. Accesing them directly gives
> >> a compiler warning. This helps in catching some BUGS
> >> due to direct partial access of these split fields.
> > 
> > Ugh.  I don't like this typedef at all. It just makes the data type more
> > confusing.
> 
> 
> Confusing enough to make people look at them more carefully.
> 
> 
> 
> > 
> > Why not just change the name of bg_block_bitmap to something like
> > bg_block_bitmap_lo or _bg_block_bitmap?  It should be clear from the
> > name that it shouldn't be used without careful consideration.
> > 
> 
> even if we rename the variables, I guess we would like to have helper functions
> for accessing these values. That would mean the code is finally going to look more
> or less the same except the typedef.

I see that as a good thing.  The typedef is the part I don't like.

> But the typedef actually save us from serious
> misuse of these variables.

You could just as easily write code that misuses bg_block_bitmap->value,
as you could bg_block_bitmap_lo.  I actually think using a name that
describes that it's only half-a-value is more clear.

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center

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