June 2018 | The Old New Thing

2018 mid-year link clearance

Raymond Chen June 29, 2018 Jun 29, 2018 06/29/18

And a list of my recent new One Dev Question videos. The One Dev Minute folks managed to con Larry Osterman into recording some short videos for them. (Second video.) So if you're sick of me, you can go check those out...

How can I detect from the preprocessor what a macro’s definition is?

Raymond Chen June 28, 2018 Jun 28, 2018 06/28/18

It is common that a preprocessor macro chooses between multiple behaviors based on various other controlling macros. Suppose you want to check at compile time how these macros are defined. Is there a way to do string comparisons in the preprocessor, something like this? I'll get it out of the way up front: Instead of trying to parse the ...

Lock free many-producer/single-consumer patterns: A work queue of distinct events, order not important, follow-up question

Raymond Chen June 27, 2018 Jun 27, 2018 06/27/18

When I discussed the work queue of distinct events, order not important, commenter JDG noted that there's a sequence of events that can result in a spurious wake-up. "Is this spurious wake just a necessary evil to keep the algorithm simple? It looks harmless; the way the consumer function is written looks threadsafe to me." Spurious wakes ...

Taking advantage of the asymmetry of offline compression

Raymond Chen June 26, 2018 Jun 26, 2018 06/26/18

Online compression is a difficult balancing act. Time you spend trying to get good compression is time the user could have been using to do something useful. For the same reason, the decompression algorithm needs to be relatively fast as well. And since files support random access, you need to be able to compress and decompress an arbitrary ...

The cost/benefit analysis of comparing before an assignment

Raymond Chen June 25, 2018 Jun 25, 2018 06/25/18

Consider these two code fragments: Which is faster? The answer to that question is "It depends." Fragment 2 introduces extra work (a compare and a branch), and depending on the pattern of comparison results, the branch predictor might or might not have trouble predicting the result of the comparison. From the branch predictor's point ...

How I learned to type

Raymond Chen June 22, 2018 Jun 22, 2018 06/22/18

Tomorrow is the 150th anniversary of the granting of United States patent 79,265 to Christopher Latham Sholes for a type-writing machine. My daughter asked me how I learned to type. I told her that I learned on a typewriter. This led to a lot of follow-up questions, starting with "What's a typewriter?" It was an Adler Junior typewriter, ...

What can influence how much stack is consumed when sending a message?

Raymond Chen June 21, 2018 Jun 21, 2018 06/21/18

Last time, we looked at a simple program that recursively sent itself a message, and we wondered, "Which will run out first? The user-mode stack or the kernel-mode stack?" Some of the calculations are under your control, but others can change at runtime. If the destination window belongs to the same thread as the sender, and there are no ...

When I intentionally create a stack overflow with <CODE>SendMessage</CODE>, why do I sometimes not get a stack overflow?

When I intentionally create a stack overflow with `SendMessage`, why do I sometimes not get a stack overflow?

Raymond Chen June 20, 2018 Jun 20, 2018 06/20/18

Take our scratch program and make these changes: This program enters infinite recursion upon receipt of the WM_APP message by sending itself another copy of the same message. We add one to the returned value to make sure there's no tail call elimination. After the program creates the window, it starts the death spiral by sending the first ...

Microspeak: knobs

Raymond Chen June 19, 2018 Jun 19, 2018 06/19/18

Recall that Microspeak is not merely for jargon exclusive to Microsoft, but also for jargon that you need to know because nobody will explain it to you. Here are some citations. This class has a lot of knobs and controls to support many scenarios, but are they all necessary? The controls have a number of events and knobs to allow you to ...

Woodworking, the opposite of software development

Raymond Chen June 18, 2018 Jun 18, 2018 06/18/18

While waiting for the BoltBus, I met a former software developer, who said that he's now a carpenter. Specifically, he makes furniture out of wood, so a more precise term for his type of work would be something like woodworking. He says he quit software because customers would keep making change requests on short notice, even for features he ...

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