Long division, part two

This is a sequel to my 2009 post about division of long integers.

I am occasionally asked why this code produces a bizarre error message:

Console.WriteLine(Math.Round(i / 6000000000, 5));

Where i is an integer.

The error is:

The call is ambiguous between the following methods: 
'System.Math.Round(double, int)' and 'System.Math.Round(decimal, int)'

Um, what the heck? Continue reading

Nostalgia, horror, and a very old bug

My next article about graph traversal is pre-empted by this breaking news; I’ll pick up that series again soon.

Yesterday morning a coworker forwarded to me an article about a recently patched security hole in Windows, and wondered if I had any thoughts on it. Oh, did I! I read about the exploit with an odd mixture of nostalgia — because I worked on the code in question back in the 1990s — and horror at how long this exploitable bug had been in Windows.

To be clear, I did not write the actual exploitable code; it predates my time at Microsoft. But I was worried while I was reading the article that it might turn out to be my bad! This is the second time that has happened to me, and it is not a pleasant feeling.

Coverity has a research team devoted specifically to security-impacting bugs, and they were kind enough to ask me to write up my thoughts for their blog. You can read about my guess at what the buggy code looked like here.

If you have examples of “missing restore”-style bugs — security-impacting or not — in real-world code in any language, I would love to see them. Please leave examples in the comments here or on the security blog. Thanks!

ATBG: randomness

Today on the Coverity Development Testing Blog’s continuing series Ask The Bug Guys I’m turning it around and asking you to figure out why a seemingly correct and totally awesome implementation of random.Next has a serious bug. That’s right, it’s everyone’s favourite game, Spot the Defect! Can you figure out where I wrote a bug without running the program? Check it out.

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ATBG: Ontogeny, phylogeny and virtual methods

I’m back! As always, I had a delightful August visiting friends and relatives in Canada. It was even more fun than usual because I’ve got a new boat. That is, a new-to-me boat; the boat is almost as old as I am. It’s a 1976 avocado-green Hobie 16. Here’s a video I shot of my first time trying it out: (I recommend watching it in HD resolution.)

Well enough chit-chat, back to programming language design. Today on the Coverity Development Testing Blog’s continuing series Ask The Bug Guys I’ll discuss how C++ is like a discredited theory of evolutionary biology and why that means you should not call a virtual method in a constructor.

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