linux-kernel - Re: [PATCH v2] iio: Fix uninitialized variable

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Message-ID: <0ec5fd64-a172-4054-a2ef-1c12db41beb5@gmail.com>
Date: Fri, 11 Oct 2024 21:32:38 +0200
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Vasileios Aoiridis <vassilisamir@...il.com>
Cc: "Yo-Jung (Leo) Lin" <0xff07@...il.com>,
 linux-kernel-mentees@...ts.linuxfoundation.org, ricardo@...liere.net,
 skhan@...uxfoundation.org, Jonathan Cameron <jic23@...nel.org>,
 Lars-Peter Clausen <lars@...afoo.de>, Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Angel Iglesias <ang.iglesiasg@...il.com>, Adam Rizkalla
 <ajarizzo@...il.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v2] iio: Fix uninitialized variable

...

> 
> Hi everyone!
> 
> So if you check also the conversations that we had here [1] and in the
> previous versions, indeed the idea behind the offset is to use it as an
> self-explanatory index to a char buffer that holds in fact s32 variables.
> 
> The data->buf here holds the values that have just been read from the
> sensor. If you check on the channel specification of this sensor,
> you will see ".realbits = 24" in both values that the sensor returns so
> hence the value 3.
> 

So you are using 3 = 24 bits, but s32 not as 4 bytes? the whole thing
would have turned into sensor_data[0], sensor_data[4], and no variables
implied, correct? But I am discussing too much for something that in the
end is more or less the same, I am fine with this proposal.

> I am not sure if it makes sense to use a macro here for each one of the
> 3's that are going to be used only one time each and in order to be more
> "consistent". But I might have a wrong view on this one so feel free to
> correct me!
> 
> For the initialization of the offset indeed, it was already mentioned
> here [2] this morning, but on a different patch!!! I couldn't get this
> error though with gcc...
> 
> Cheers,
> Vasilis
> 

At least for the things I do in the kernel, clang catches more issues
than gcc. Sometimes even gcc will not complain, and clang will fail to
compile (e.g. a goto before a cleanup attribute).

And if you run smatch before sending the series, you might discover a
couple of extra "surprises".

Best regards,
Javier Carrasco