Re: (0 == foo), rather than (foo == 0)

[Peter Williams]

Linus Torvalds wrote:
> On Thu, 11 Mar 2004, Peter Williams wrote:
>
> > Richard B. Johnson wrote:
> >
> > > People who develop kernel code know the difference between
> > > '==' and '=' and are never confused my them.
> >
> > And you never make typing mistakes?  That's admirable or should I say 
> > incredible.
>
>
> The thing is, people tend to make fewer typing mistakes of that kind, than 
> just plain logic errors from not thinking right about something.
>
> And while "0 == foo" may be logically the same thing as "foo == 0", the 
> fact is, the latter is what people are used to seeing. And by being used 
> to seeing it, they have an easier time thinking about it.
>
> As a result, using the former just tends to increase peoples confusion by
> making code harder to read, which in turn tends to increase the chance of 
> bugs.
>
> So don't do it. The kind of bug that the "0 == x" syntax protects against
> is LESS LIKELY to happen than the kind of bug it tends to cause.
>
> 		Linus

OK.  I'll change all of such occurences in our EBS patches.

As somebody pointed out -Wall will (help) detect most of these errors by 
suggesting () be placed around any expression of the form a = b that 
occurs inside a simple boolean expression which will cause those people 
who care about eliminating warning messages to reevaluate the code and 
make sure they really meant a = b and replace it with (a = b) to get rid 
of the warning error.

The reason that I say "most" rather than "all" is (that testing shows) 
that if the a = b is part of a more complex expression and is already in 
() in order to (for instance) ensure the desired precedence -Wall will 
not flag it as a possible problem.

Peter
--
Dr Peter Williams, Chief Scientist                peterw@xxxxxxxxxx
Aurema Pty Limited                                Tel:+61 2 9698 2322
PO Box 305, Strawberry Hills NSW 2012, Australia  Fax:+61 2 9699 9174
79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com


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