The Old New Thing
Practical development throughout the evolution of Windows.
Latest posts
I didn't realize that it was International Group B Strep Awareness Month
I guess they're not doing a particularly good job of creating awareness because it wasn't until I consulted the 2006 National Health Observances calendar that the month of July is International Group B Strep Awareness Month. For some reason, July and August are pretty light on the health observances calendar. Maybe because people are on summer vacation. Who decides whether a particular health observance merits a day, a week, or a month? You'd think they'd save the months for the really big issues, seeing as there are only twelve of them. And for some reason, ultraviolet radiation gets two months. May is Ultrav...
Calling an imported function, the naive way
An import library resolves symbols for imported functions, but it isn't consulted until the link phase. Let's consider a naive implementation where the compiler is blissfully unaware of the existence of imported functions. In the 16-bit world, this caused no difficulty at all. The compiler generated a far call instruction and left an external record in the object file indicating that the address of the function should be filled in by the linker. At that time, the linker realizes that the external symbol corresponds to an imported function, so it takes all the call targets, threads them together, and creates an ...
Buy me some peanuts and a set of double-pointed 2's
It's the second annual Stitch 'n Pitch at Safeco Field. Stitch n' Pitch events for other cities can be found on the Stitch n' Pitch web site. (Channeling Lynne Truss: Ahem, people, the spelling of the middle word is 'n' with an apostrophe fore and aft.) [10am: Fixed sepleling.] Seattle Times readers Dave Butner and Mike Wilson took issue with the event (though Mr. Wilson's outrage bordered on satirical). To me, baseball is like soccer: It's a game whose primary draw is not the actual scoring but rather the anticipation that a run might be scored. It's in the tension that builds as scoring opportunities devel...
Rethinking the way DLL exports are resolved for 32-bit Windows
Over the past few days we've learned how 16-bit Windows exported and imported functions from DLLs and that the way functions are exported from 32-bit DLLs matches the 16-bit method reasonably well. But the 16-bit way functions are imported simply doesn't work in the 32-bit world. Recall that in 16-bit Windows, the fixups for an imported function are threaded through the code segment. This works great in 16-bit Windows since there was a single address space: Code segments were shared globally, and once a segment was loaded, each process could use it. But 32-bit Windows uses separate address spaces. If the fixu...
The traffic gods are punishing me for bicycling
It happened again. The last time I participated in a bicycle ride that started in Seattle, I got stuck in highway traffic both going out and coming back. The 520 bridge was closed for inspection so everybody was taking the I-90 bridge instead. But traffic at the western terminal of I-90 was backed up because the Alaska Way Viaduct was closed for some sort of fundraiser walk-a-thon. And then, after the ride was over, I got stuck in traffic on the return trip as well because the Mariners baseball game had just let out, and that on top of all the traffic created by the 520 bridge being closed. This weekend, head...
Exported functions that are really forwarders
Last time, we saw how the way Win32 exports functions is pretty much the same as the way 16-bit Windows exports functions, but with a change in emphasis from ordinal-based exports to name-based exports. This change in emphasis is not expressed anywhere in the file format; both 16-bit and 32-bit DLLs can export either by name or by ordinal (or by both), but the designers of Win32 were biased in spirit in favor of name-only exports. But there is a new type of exported function in Win32, known as a forwarder. A forwarder looks just like a regular exported function, except that the entry in the ordinal export tab...
How are DLL functions exported in 32-bit Windows?
The designers of 32-bit Windows didn't have to worry quite so much about squeezing everything into 256KB of memory. Since modules in Win32 are based on demand-paging, all you have to do is map the entire image into memory and then run around accessing the parts you need. There is no distinction between resident and non-resident names; the names of exported functions are just stored in the image, with a pointer (well, a relative virtual address) to the name stored in the export table. Unlike the 16-bit ordinal export table, the 32-bit ordinal export table is not sparse. If your DLL exports two functions, one as ...
The day the peloton lost its way
It's the one time a year that more than fifty people in the United States actually give a hoot about bicycle racing. Yes, it's the Tour de France. (Follow the racers live via GPS!) But this story isn't about the Tour. It's about Stage 4 of the 2005 ENECO Tour. You can follow along with the live report. Everything was going pretty much like a typical racing stage, until time code 13:55. Veikkanen is now gone from the back of the lead group, but the peloton appears to have taken a wrong turn!! The peloton is just stopped in the road. nobody knows what happened, riders are getting off their bikes. Zabe...
How were DLL functions imported in 16-bit Windows?
A threaded linked list.