Kernel prepatch 3.11-rc4 [LWN.net]

Kernel prepatch 3.11-rc4

Posted Aug 6, 2013 7:32 UTC (Tue) by kugel (subscriber, #70540)
In reply to: Kernel prepatch 3.11-rc4 by error27
Parent article: Kernel prepatch 3.11-rc4

How can a yoda condition possible "hide more bugs than it fixes"?

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Kernel prepatch 3.11-rc4

Posted Aug 6, 2013 10:01 UTC (Tue) by khim (subscriber, #9252) [Link] (4 responses)

Easy: when you see on Yoda condition it's harder for you to notice that code does something syntactically correct yet semantically wrong. Uses address of wrong variable (which is pushed to the end of expression with Yoda condition), for example.

Kernel prepatch 3.11-rc4

Posted Aug 7, 2013 9:25 UTC (Wed) by dgm (subscriber, #49227) [Link] (3 responses)

How can you tell if an expression is correct if you don't read them in full?

Kernel prepatch 3.11-rc4

Posted Aug 7, 2013 9:32 UTC (Wed) by mpr22 (subscriber, #60784) [Link] (2 responses)

You can't. Which is why making expressions hard to read is a bad idea.

Kernel prepatch 3.11-rc4

Posted Aug 14, 2013 13:24 UTC (Wed) by dgm (subscriber, #49227) [Link] (1 responses)

Which of those expressions is harder to read:

A == B

B == A

Kernel prepatch 3.11-rc4

Posted Aug 14, 2013 15:18 UTC (Wed) by mathstuf (subscriber, #69389) [Link]

Let's use some actual examples:

> i == container.end()
> container.end() == i

> result == (2 * idx * idx)
> (2 * idx * idx) == result

> pivot < container.size() / 2
> container.size() / 2 > pivot

> speed > threshold
> threshold < speed

In all of these cases except the last, I would naturally write the first line[1]. I think they read more naturally. To reduce errors, I have const on every variable possible (containers I have to build are the exception (I can't wait for initializer lists)), so my code tends to follow SSA a lot[2].

[1]I try and order all orderings to use '<' since I think "(a > min) && (a < max)" is harder to parse and using one comparison everywhere helps keep the mental overhead low.
[2]It helps in debugging since all intermediates are named and you don't get things like i->first.second.second in the middle of lines and have to backtrack what the iterator's pair nesting is all the time.