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From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: "Morten Brørup" <mb@smartsharesystems.com>,
	"Thomas Monjalon" <thomas@monjalon.net>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"ferruh.yigit@amd.com" <ferruh.yigit@amd.com>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"bruce.richardson@intel.com" <bruce.richardson@intel.com>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>
Subject: RE: Coding Style for local variables
Date: Thu, 20 Jun 2024 08:09:11 +0000	[thread overview]
Message-ID: <978413ec22cb4b76872bd85f3588e5f3@huawei.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35E9F53F@smartserver.smartshare.dk>



> > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> >
> > 10/06/2024 18:31, Konstantin Ananyev:
> > > Morten said:
> > > > The coding style guide says:
> > > >
> > > > "Variables should be declared at the start of a block of code rather than
> > in the middle. The exception to this is when the variable is
> > > > const in which case the declaration must be at the point of first
> > use/assignment. Declaring variable inside a for loop is OK."
> > > >
> > > > Since DPDK switched to C11, variables can be declared where they are used,
> > which reduces the risk of using effectively uninitialized
> > > > variables. "Effectively uninitialized" means initialized to 0 or NULL
> > where declared, to silence any compiler warnings about the use of
> > > > uninitialized variables.
> > > >
> > > > Can we please agree to remove the recommendation/requirement to declare
> > variables at the start of a block of code?
> > >
> > > I know that modern C standards allow to define variable in the middle.
> > > But I am strongly opposed to allow that in DPDK coding style.
> > > Such practice makes code much harder to read and understand (at least for
> > me).
> >
> > Yes it is convenient to know that all variables are described
> > in a known place, just after function parameters.
> >
> > There is also a consistency concern.
> >
> > Old contributors like to be in a comfort zone,
> > 	and we don't want to lose old contributors.
> > New contributors may be refrained by old rules,
> > 	and we would like to get more new contributors.
> >
> > So that's a tricky decision.
> >
> 
> Independent research shows that readability is improved by declaring local variables as close as possible to their first use:
> https://barrgroup.com/72-initialization#footnote12

Hmm... seems  they don't provide any data to back up their statements.
Specially that one sounds weird for me:
" Too many programmers assume the C run-time will watch out for them, e.g., by zeroing the value of uninitialized variables on system startup."
Why on earth people would assume that?
And what exactly means 'too many? 1%? 10%? 90%? 

> 
> Old people (like myself) need to unlearn their bad old habits (originating from limitations in old C standards), and embrace modern
> methods to reduce the risk of introducing bugs.

Allowing to define variables in the middle of the code by itself wouldn't prevent of use of un-initialized variables.
From other side - compilers are quite good these days to catch such bugs.
So I don't think it is a completing argument..    
 



  reply	other threads:[~2024-06-20  8:09 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-10 15:10 Morten Brørup
2024-06-10 16:11 ` Tyler Retzlaff
2024-06-10 16:31 ` Konstantin Ananyev
2024-06-20  0:38   ` Thomas Monjalon
2024-06-20  7:53     ` Morten Brørup
2024-06-20  8:09       ` Konstantin Ananyev [this message]
2024-06-20  9:02         ` Morten Brørup
2024-06-20 14:45           ` Stephen Hemminger
2024-06-11 15:10 ` Ferruh Yigit
2024-06-11 15:50   ` Stephen Hemminger
2024-06-17 14:38 ` Bruce Richardson

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