linux-kernel - Re: InfiniBand-ocrdma: Delete unnecessary variable initialisations in 11 functions

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Date:	Fri, 15 Jan 2016 17:24:50 +0100
From:	SF Markus Elfring <elfring@...rs.sourceforge.net>
To:	linux-rdma@...r.kernel.org, Leon Romanovsky <leon@...n.nu>
Cc:	Devesh Sharma <devesh.sharma@...gotech.com>,
	Doug Ledford <dledford@...hat.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Mitesh Ahuja <mitesh.ahuja@...gotech.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Selvin Xavier <selvin.xavier@...gotech.com>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: InfiniBand-ocrdma: Delete unnecessary variable initialisations in
 11 functions

> GCC supported it before 1999 when I saw it first time. My assumption
> that in 2016 all compilers are doing such optimization now.

Interesting …

> I would be glad to hear an example of modern compiler which doesn't
> support this simple optimization.

Would you like to take into account any other source code analysis approaches?

>> Will any configuration parameters and command arguments become relevant
>> to improve also a corresponding software comparison?
> 
> Please suggest us, you are proposing this change, and not me.

Which combination of hardware and software versions would you find representative
for a corresponding system check?

>>> The proposed change won't affect performance at all.
>>
>> Will unneeded variable assignments be really optimised away by default?
> 
> Yes

Can it be that this result will depend on special parameters so that data flow
analysis and optimisation will be performed in the way you seem to expect?

> If you are interested in saving space of one latter, you need to take into
> account git database increase, do you?

There are also other aspects to consider:

* Do you insist to initialise a return code at the beginning of every function
  with a non-void return type?

* Does each bit of extra information can result also in unwanted consequences?

* Is this a specific source code review concern?

* Can this software be improved a bit more only if we dare to talk about
  potential update candidates?

Regards,
Markus