June 2018 | The Old New Thing

2018 mid-year link clearance

Raymond ChenJune 29, 2018Jun 29, 201806/29/18

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 ChenJune 28, 2018Jun 28, 201806/28/18

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 ChenJune 27, 2018Jun 27, 201806/27/18

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 ChenJune 26, 2018Jun 26, 201806/26/18

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 ChenJune 25, 2018Jun 25, 201806/25/18

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 ChenJune 22, 2018Jun 22, 201806/22/18

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 ChenJune 21, 2018Jun 21, 201806/21/18

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 data-lazy-src=

SendMessage, 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 ChenJune 20, 2018Jun 20, 201806/20/18

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 ChenJune 19, 2018Jun 19, 201806/19/18

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 ChenJune 18, 2018Jun 18, 201806/18/18

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 ...

The Old New Thing