Using Redundancies to Find Errors

gsbarnes writes "Two Stanford researchers (Dawson Engler and Yichen Xie) have written a paper (pdf) showing that seemingly harmless redundant code is frequently a sign of not so harmless errors. Examples of redundant code: assigning a variable to itself, or dead code (code that is never reached). Some of their examples are obvious errors, some of them subtle. All are taken from a version of the Linux kernel (presumably they have already reported the bugs they found). Two interesting lessons: Apparently harmless mistakes often indicate serious troubles, so run lint and pay attention to its output. Also, in addition to its obvious practical uses, Linux provides a huge open codebase useful for researchers investigating questions about software engineering."

Errors like...

[Anonymous Coward]

This really old Slashdot logo [slashdot.org] still in use over on Team Slashdot's page [distributed.net] on distributed.net.

Patience!

[houseofmore]

"...dead code (code that is never reached)"

Perhaps it's just shy!

And their other findings ...

[kruetz]

They also found that:

Russian errors cause code
Incorrect code causes errors
Missing code causes errors
Untested code causes errors
Redundant codec causes redundancies
Driver code causes headaches
C code causes buffer overflows
Java code causes exceptions
Perl code causes illiteracy
Solaris code causes rashes
Novell code causes panic attacks
Slashdot code causes multiple reposts
Slashdot articles cause poor-quality posts
Microsoft code causes exploits
Apple code causes user cults
Uncommented code causes code rage
RIAA code causes computers to stop functioning
(Poor idea causes long, desperate post)

IN SOVIET RUSSIA...

[Anonymous Coward]

Errors find YOU! find YOU!

Most prevalent source of redundant code....

[1nv4d3r]

Three letters: NIH.

Now, if you'll excuse me, I've got to get back to my text editor project.

Finding errors in your code

[Amsterdam Vallon]

Isn't this the job of that smart dude down the hall who runs Lunix computers and reads some Slash Period website or something?

Well, at least that's how I finish all my projects.

A good editor...

[yintercept]

A good editor could easily cut that article in half without loss of any information.

Intentional redundant code

[1nv4d3r]

I've seen this (they were fired the next month):

// and now to boost my LOC/Day performance...
x += 0;
x += 0;
x += 0;
x += 0;
x += 0;
x += 0;

It actually caused a bug 'cuz they accidentally left the '+' off one of the lines. What an idiot.

Redundancy?

[kubrick]

Ummm... surely if any story should be duped in the near future, it's this one. Please submit story suggestions accordingly.

Re:redundant?

[Anonymous Hack]

a=a superfluous? HOW DARE YOU! a=a is the foundation from which everything else derives! a=a proves that the only logical course of action is to TAKE! a=a is the single, most important, non-patented discovery since the wheel!

Now, i'm off to create a new form of steel that will revolutionize the railroad industry!

PDF usually crashes my computer

[Anonymous Coward]

Maybe PDF has too much redundant code.

Re:lint is horrible

[Anonymous Coward]

Stop bragging, Linus.

Re:Using redundant code to find errors

[nebbian]

I was going to moderate this but there's no +1 Redundant.

vi!

[gregstoll]

vi could do it!

Re:Patience!

[heikkile]

"...dead code "

It's not dead - it is resting. It is pining for the fjords.

Even the smallest program...

[OttoM]

This is widely known:

1. Every programs contains bugs.
2. Every program contains redundancies and so can be made smaller without changing behavior.

Therefore the empty program is redundant but still buggy.

Re:How to Avoid Mistakes? Practical Advice?

[Ed Avis]

I think it is the software version of 'zero tolerance'. Get rid of beggars and squeegee merchants and you make the more serious crimes (bugs) easier to detect and solve. Or something like that.

Re:Error checking compilers

[Anonymous Coward]

I understand that there are non-C compilers out there that actually detect code errors without running a separate utility. Amazing!

Silence! We will not tolerate such subversive thoughts here.