March 2018 | The Old New Thing

Why is it cheaper to fly out of Vancouver for spring break instead of Seattle, while also being cheaper to fly out of Seattle for spring break instead of Vancouver?

Raymond ChenMarch 30, 2018Mar 30, 201803/30/18

Some relatives from Vancouver, British Columbia came to visit, and we mentioned that when we fly out on vacation for spring break, we found that the airplane tickets are much cheaper if we drive up to Canada and fly out of Vancouver International Airport. On the other hand, they noted that when they fly out on vacation for spring break, they ...

How do I choose between the strong and weak versions of compare-exchange?

Raymond ChenMarch 30, 2018Mar 30, 201803/30/18

Last time, we left with the question of when you should prefer the strong version of compare-exchange as opposed to the weak version. It comes down to whether spurious failures are acceptable and how expensive they are. In the example given in the presentation, the cost of a spurious failure is very low: Recovering from a spurious failure ...

Geology throwdown: The whisper of the rocks

Raymond ChenMarch 29, 2018Mar 29, 201803/29/18

The Proceedings of the National Academy of Sciences is a serious scientific journal, whose published papers undergo rigorous peer review. This week's issue shows that this doesn't mean that the titles can't be snarky. Letters (Online Only) Listen to the whisper of the rocks, telling their ancient story Paul J. ...

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What’s up with `compare_exchange_weak` anyway?

Raymond ChenMarch 29, 2018Mar 29, 201803/29/18

It's handy for certain classes of processors.

When I memcpy a struct into a std::atomic of that struct, why does the result not match?

Raymond ChenMarch 28, 2018Mar 28, 201803/28/18

Consider the following code: This code tries to load a Point3D structure from a file directly into a std::atomic. However, the customer found that the results were not properly loaded and suspected there may a bug in the ReadFile function, because the value that should have been in the z member ended up in y, the value that should have ...

The WMI root node is just a node in the WMI namespace

Raymond ChenMarch 27, 2018Mar 27, 201803/27/18

A security vulnerability report arrived that went roughly like this: There is a serious zero-day security vulnerability in the WMIC.EXE program. It does not check whether the user has administrative privileges before granting access. Simply sign in as a standard user and run the wmic program. Observe from the prompt that it gives you root ...

A rare opportunity to fact-check the “celebrity net worth” sites

Raymond ChenMarch 26, 2018Mar 26, 201803/26/18

The late John Mahoney left an estate worth "north of $5 million" according to documents obtained by celebrity news site TMZ. This gave me a rare opportunity to fact-check various "celebrity net worth" sites. My guess is that everybody copied their data from celebritynetworth.com, because their estimates all agree with the estimate of ...

What are the odds that two pull requests get completed at the exact same time?

Raymond ChenMarch 26, 2018Mar 26, 201803/26/18

The so-called Fall Creators Update of Windows 10 encompassed four million commits in half a million pull requests. A project of this size exposes issues in infrastructure by stressing it to levels previously considered unimagineable. One of the issues uncovered by hosting the Windows repo on Visual Studio Team Services (VSTS) is that of pull ...

Stop cherry-picking, start merging: Index

Raymond ChenMarch 23, 2018Mar 23, 201803/23/18

For one-stop reading.

Stop cherry-picking, start merging, Part 10: Web-based workflow for Azure DevOps (formerly VSTS)