Browse by Tags

Every so often, somebody "discovers" an alleged security vulnerability in the Format­Message function. You can try it yourself: #include <windows.h> #include <stdio.h> char buf[2048]; char extralong[128*1024]; int __cdecl main(int argc, char **argv) { memset(extralong, 'x', 128...

A customer was using memory-mapped files and was looking for information as to whether access to the memory-mapped data modifies the value returned by Get­Last­Error . A member of the kernel team replied, "No, memory-mapped I/O does not ever change the value returned by Get­Last­Error...

Suppose your PATH environment variable looks like this: C:\dir1;\\server\share;C:\dir2 Suppose that you call LoadLibrary("foo.dll") intending to load the library at C:\dir2\foo.dll . If the network server is down, the LoadLibrary call will fail. Why doesn't it just skip the bad directory in...

A customer reported an incompatibility in Windows 7: If A: is a floppy drive and they call Load­Library("A:\\foo.dll") and there is no disk in the drive, the Load­Library call fails with the error ERROR_ NOT_ READY . Previous versions of Windows failed with the error ERROR_ MOD_ NOT_ FOUND...

A customer designed a system which uses shared memory. Specifically, for each database file, they create a corresponding shared memory block of, say, 200 MB . Multiple clients which connect to the same database file use the same shared memory block. Naturally, if two processes each access the same database...

A while back, I linked to a talk by Silviu Calinoiu on the fault-tolerant heap . But what if you don't want the fault-tolerant heap? For example, during program development, you probably want to disable the fault-tolerant heap for your program: If the program is crashing, then it should crash so...

Friday asks whether OANOCACHE can be used for non-debug purposes, say to improve stability and/or speed . You can try, but it's not recommended. For one thing, it probably damages stability, because there are many applications out there which unwittingly rely on the BSTR cache to protect them from...

There are two flags you can pass to the Create­File function to provide hints regarding your program's file access pattern. What happens if you pass either of them, or neither? Note that the following description is not contractual. It's just an explanation of the current heuristics (where...

I have an ongoing conflict with my in-laws. Their concept of the correct amount of food to have in the refrigerator is "more than will comfortably fit." Whenever they come to visit (which is quite often), they make sure to bring enough food so that my refrigerator bursts at the seams, with vegetables...

Commenter Worf remarked, " My one wish is that #warning would be supported ." I always find it interesting when people say "I wish that Microsoft would stop following standards," since the #warning directive is nonstandard. The Microsoft C/C++ compiler implements the feature in a method...

A customer reported that they were receiving some assertion failures because the Heap­Free function was failing with what they believed to be a valid heap block, and the Get­Last­Error function reported that the reason for failure was ERROR_ POSSIBLE_ DEADLOCK . What's going on? One...

When the Dll­Main function receives a reason code of DLL_ PROCESS_ DETACH , the increasingly-inaccurately-named lpReserved parameter to is used to indicate whether the process is exiting. And if the process is exiting, then you should just return without doing anything. No, really. ...

Last week we looked at menu drag/drop. Another little-used menu feature added in Windows 2000 is the ability to show context menus on menus. The message is WM_ MENU­RBUTTON­UP and the flag is TPM_ RECURSE . Let's demonstrate with a simple program. Start with the scratch program , and...

In order to do drag-drop rearrangement of menus, you need four things, most of which we already know how to do. Dragging an item out of a menu. Check . Dropping an item into a menu. Check . Connecting the drag with the drop. Rearranging menu items in response to the operation. Let's...

Last time, we looked at using the MNS_ DRAG­DROP style for dragging items out of a menu . Today, we'll look at dropping them in. Take the program from last time and make the following additions. First, let's add a second item to the menu. // resource header file #define IDM_MAIN 1 #define...

Windows 2000 introduced the MNS_ DRAG­DROP menu style, which permits drag/drop operations in a menu. Nobody uses this style, probably because it's totally undiscoverable by the end-user. But I'll write a sample program anyway. Mind you, I knew nothing about the MNS_ DRAG­DROP menu style...

Over the years, I've seen a bunch of coding anti-patterns. I figured maybe I'll share a few. Today, I'll introduce what I'm calling the for-if anti-pattern, also known as " We'll sell you the whole seat, but you'll only need the edge ." This is a special case of the for-case anti-pattern, where all...

A customer was having trouble obtaining information from a shortcut file. "Here is a sample program that tries to print the target of a shortcut file, but it only gets the file name without a directory. How do I get the full path?" IShellLink *psl; ... code that loads the IShellLink omitted .....

Given an LCID , how does one determine whether the language lays out left-to-right or right-to-left? One suggestion was simply to hard-code the list of known right-to-left languages, and if the language isn't on the list, then assume that it is left-to-right. This technique is clearly fragile, because...

There is a class of messages which are generated on demand rather than explicitly posted into a message queue. If you call Get­Message or Peek­Message and the queue is empty, then the window manager will look to see if one of these generated-on-demand messages is due, messages like WM_ TIMER...

In unix, file descriptors are inherited by child processes by default. This wasn't so much an active decision as it was a consequence of the fork/exec model. To exclude a file descriptor from being inherited by children, you set the FD_ CLO­EXEC flag on the file descriptor. Win32 sort of works...

The last time I mentioned programmatic access to SkyDrive was last June , where I noted that the interface was given the confusing name Messenger Connect. At least now they renamed it to Live Connect , which is slightly less confusing. The SkyDrive folks have been pretty busy lately. A few days...

A customer wanted a way to determine whether a particular window is modal. They listed a few methods they had tried but found that it didn't work and asked for assistance. As Eric Lippert is fond of saying, " First, write your spec ." Until you know what you want, you won't know how to get it. ...

A customer contacted me to tell a story and ask a question. The customer discovered that in their code base, all calls to Queue­User­Work­Item passed the WT_ EXECUTE­LONG­FUNCTION flag, regardless of whether the function actually took a long time or not. Their program creates a large...

You're running your program, and then it suddenly exits with the message This application has requested the Runtime to terminate it in an unusual way . What happened? That message is printed by the C runtime function abort , the same function that also causes your program to terminate with...