The Old New Thing
Practical development throughout the evolution of Windows.
Latest posts
Liquefied NBA points apparently cannot be sold on eBay
Of course we don't find this out until somebody tries. (Google cache for a limited time only.)
Waiting for all handles with MsgWaitForMultipleObjects is a bug waiting to happen
The and functions allow you to specify whether you want to want for any or all of the handles (either by passing or by passing , accordingly). But you never want to wait for all handles. Waiting for all handles means that the call does not return unless all the handles are signalled and a window message meeting your wake criteria has arrived. Since you are typically waiting for messages out of a sense of obligation (keeping the UI thread responsive) rather than one of expectation, even if all the handles you pass become signalled, your program will still stall until a window message arrives. (And if you thoug...
Stephen Tolouse's reminiscences of Windows 95 RTM day
Stephen Tolouse (known around Microsoft as "stepto", pronounced "step-toe") from the Microsoft Security Response Center reminisces about Windows 95 RTM. Stephen mentions that "the build numbers were artificially inflated to reach 950". There's actually a technical reason for this inflation, which I intend to write about when I have the time to give the topic the treatment it deserves.
Pumping messages while waiting for a period of time
We can use the function (or its superset ) to carry out a non-polling "sleep while processing messages". This function pumps messages for up to milliseconds. The kernel of the idea is merely to use the function as a surrogate for , pumping messages until the cumulative timeout has been reached. There are a lot of small details to pay heed to, however. I've linked them to earlier postings that discuss the specific issues, if you need a refresher. The you might find gratuitous, but you'll change your mind when you realize that users might press a keyboard accelerator while you're sleeping, and you presumabl...
Welcome to the United States, unless you're a Canadian technologist who is an invited guest at a Microsoft conference, in which case, keep out
Vancouver technologist Darren Barefoot was invited to Redmond by the MSN Search team but was stopped by Immigration and denied entry. Ultimately, the customs agents concluded that because Microsoft was covering my flight and accommodation, I was being compensated for consulting activities. In order to enter the country, I'd need a work permit. He says Customs, but I'm pretty sure it was really Immigration that stopped him. Sorry, Darren. We miss you already. We even asked the rain to take a few days off and invited the sun out to play just for you.
You can call MsgWaitForMultipleObjects with zero handles
There is no function, but you can create your own with the assistance of the function. To wait for a message with timeout, we use the in a vacuous sense: You pass it a list of objects you want to wait for, as well as a timeout and a set of queue states, asking that the function return when any of the objects is signalled or when a message is ready. By passing no objects, the only thing left to wait for is an incoming message. Next time, we'll see how this basic idea can be used to build a slightly more complex function. [1/26: Fix call to MsgWaitForMultipleObjects; had it confused with MsgWaitForMultip...
Creepy messages in your baggage
Heather Leigh had a creepy experience with her baggage last week. The story continued yesterday. I'm watching to see how things turn out.
Performance consequences of polling
Polling kills. A program should not poll as a matter of course. Doing so can have serious consequences on system performance. It's like checking your watch every minute to see if it's 3 o'clock yet instead of just setting an alarm. First of all, polling means that a small amount of CPU time gets eaten up at each poll even though there is nothing to do. Even if you tune your polling loop so its CPU usage is only, say, a measly one tenth of one percent, once this program is placed on a Terminal Server with 800 simultaneous connections, your 0.1% CPU has magnified into 80% CPU. Next, the fact that a small snippet...
There are two types of rebates, and you need to be on the alert
Many commenters to my earlier entry on sales in France had questions about rebates. Slate explained the whole rebate thing back in 2003. The short version: There are two types of rebates, manufacturer rebates and retailer rebates. Manufacturer rebates exist because they want the retail price to go down, but they are afraid that if they just lowered the wholesale price, retailers would not pass the savings on to the consumer. A manufacturer's rebate ensures that all the benefit of the price drop goes to the consumer and not to any middle-men. Retailer rebates, on the other hand, are carefully crafted schemes de...