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winapi interview questions

Top winapi frequently asked interview questions

Objective C for Windows

What would be the best way to write Objective-C on the Windows platform?

Cygwin and gcc? Is there a way I can somehow integrate this into Visual Studio?

Along those lines - are there any suggestions as to how to link in and use the Windows SDK for something like this. Its a different beast but I know I can write assembly and link in the Windows DLLs giving me accessibility to those calls but I don't know how to do this without googling and getting piecemeal directions.

Is anyone aware of a good online or book resource to do or explain these kinds of things?


Source: (StackOverflow)

What's "wrong" with C++ wchar_t and wstrings? What are some alternatives to wide characters?

I have seen a lot of people in the C++ community(particularly ##c++ on freenode) resent the use of wstrings and wchar_t, and their use in the windows api. What is exactly "wrong" with wchar_t and wstring, and if I want to support internationalization, what are some alternatives to wide characters?


Source: (StackOverflow)

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Why in C++ do we use DWORD rather than unsigned int?

I'm not afraid to admit that I'm somewhat of a C++ newbie, so this might seem like a silly question but....

I see DWORD used all over the place in code examples. When I look up what a DWORD truly means, its apparently just an unsigned int (0 to 4,294,967,295). So my question then is, why do we have DWORD? What does it give us that the integral type 'unsigned int' does not? Does it have something to do with portability and machine differences?


Source: (StackOverflow)

Windows 7 SDK installation failure

I seem to be completely unable to install the Windows 7 SDK onto my machine, and the only solution I've found on the web is to make a swathe of registry changes. I've done this - still no success.

This is the reported error:

A problem occurred while installing selected Windows SDK components.

Installation of the "Microsoft Windows SDK for Windows 7" product has reported the following error: Please refer to Samples\Setup\HTML\ConfigDetails.htm document for further information.

Please attempt to resolve the problem and then start Windows SDK setup again. If you continue to have problems with this issue, please visit the SDK team support page at http://go.microsoft.com/fwlink/?LinkId=130245.

Click the View Log button to review the installation log.

To exit, click Finish.

There is no Samples directory to refer too, and the SDK support team don't appear to live there any longer.

How do I fix this problem?


Source: (StackOverflow)

Bring a window to the front in WPF

How can I bring my WPF application to the front of the desktop? So far I've tried:

SwitchToThisWindow(new WindowInteropHelper(Application.Current.MainWindow).Handle, true);

SetWindowPos(new WindowInteropHelper(Application.Current.MainWindow).Handle, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);

SetForegroundWindow(new WindowInteropHelper(Application.Current.MainWindow).Handle);

None of which are doing the job (Marshal.GetLastWin32Error() is saying these operations completed successfully, and the P/Invoke attributes for each definition do have SetLastError=true).

If I create a new blank WPF application, and call SwitchToThisWindow with a timer, it works exactly as expected, so I'm not sure why it's not working in my original case.

Edit: I'm doing this in conjunction with a global hotkey.


Source: (StackOverflow)

How do you configure an OpenFileDialog to select folders?

In VS .NET, when you are selecting a folder for a project, a dialog that looks like an OpenFileDialog or SaveFileDialog is displayed, but is set up to accept only folders. Ever since I've seen this I've wanted to know how it's done. I am aware of the FolderBrowserDialog, but I've never really liked that dialog. It starts too small and doesn't let me take advantage of being able to type a path.

I'm almost certain by now there's not a way to do this from .NET, but I'm just as curious how you do it from unmanaged code as well. Short of completely reimplementing the dialog from scratch, how do you modify the dialog to have this behavior?

I'd also like to restate that I am aware of the FolderBrowserDialog but sometimes I don't like to use it, in addition to being genuinely curious how to configure a dialog in this manner. Telling me to just use the FolderBrowserDialog helps me maintain a consistent UI experience but doesn't satisfy my curiosity so it won't count as an answer.

It's not a Vista-specific thing either; I've been seeing this dialog since VS .NET 2003, so it is doable in Win2k and WinXP. This is less of a "I want to know the proper way to do this" question and more of a "I have been curious about this since I first wanted to do it in VS 2003" question. I understand that Vista's file dialog has an option to do this, but it's been working in XP so I know they did something to get it to work. Vista-specific answers are not answers, because Vista doesn't exist in the question context.

Update: I'm accepting Scott Wisniewski's answer because it comes with a working sample, but I think Serge deserves credit for pointing to the dialog customization (which is admittedly nasty from .NET but it does work) and Mark Ransom for figuring out that MS probably rolled a custom dialog for this task.


Source: (StackOverflow)

Is it possible to "decompile" a Windows .exe? Or at least view the Assembly?

A friend of mine downloaded some malware from Facebook, and I'm curious to see what it does without infecting myself. I know that you can't really decompile an .exe, but can I at least view it in Assembly or attach a debugger?

Edit to say it is not a .NET executable, no CLI header.


Source: (StackOverflow)

How to find if a native DLL file is compiled as x64 or x86?

I want to determine if a native assembly is complied as x64 or x86 from a managed code application (C#).

I think it must somewhere in the PE header since the OS loader needs to know this information, but I couldn't find it. Of course I prefer to do it in managed code, but if it necessary, I can use native C++.


Source: (StackOverflow)

What is __stdcall?

I'm learning about Win32 programming, and the WinMain prototype looks like:

int WINAPI WinMain ( HINSTANCE instance, HINSTANCE prev_instance, PSTR cmd_line, int cmd_show )

I was confused as to what this WINAPI identifier was for and found:

#define WINAPI      __stdcall

What does this do? I'm confused by this having something at all after a return type. What is __stdcall for? What does it mean when there is something between the return type and function name?


Source: (StackOverflow)

How can a Metro app in Windows 8 communicate with a backend desktop app on the same machine?

In a situation where you have the UI frontend built using the new Metro style of apps for windows 8, and would like it to communicate with a .NET application running on the desktop on the same local machine (e.g. a windows service app).

What forms of interprocess communication are available between the metro app and the desktop app?

Thanks to Pavel Minaev of the Visual Studio team, who has provided some initial info here in a comment, quoted:

According to Martyn Lovell, there isn't any deliberate mechanism for that, and some that could be used for it are intentionally restricted. Named pipes aren't there, for example, nor are memory mapped files. There are sockets (including server sockets), but when connecting to localhost, you can only connect to the same app. You could use normal files in one of the shared "known folders" (Documents, Pictures etc), but that is a fairly crude hack that necessitates polling and is visible to the user. -- Pavel Minaev commenting on this issue

So failing normal approaches I was thinking of using web services or reading/writing to a database in order to get some form of communication happening, both of which seem like overkill when the processes are running on the same machine.

Is what I'm attempting here making sense? I can see a need for a metro app to be the frontend UI for an existing service which is running on the desktop. Or is it better to just use WPF for the frontend UI running on the desktop (i.e. a non-metro app).


Source: (StackOverflow)

Windows threading: _beginthread vs _beginthreadex vs CreateThread C++

What's a better way to start a thread?

I'm trying to determine what are the advantages/disadvantages of _beginthread, _beginthreadex and CreateThread. All of these functions return a thread handle to a newly created thread, I already know that CreateThread provides a little extra information when an error occurs (it can be checked by calling GetLastError)... but what are some things I should consider when I'm using these functions?

I'm working with a windows application, so cross-platform compatibility is already out of the question.

I have gone through the msdn documentation and I just can't understand, for example, why anybody would decide to use _beginthread instead of CreateThread or vice versa.

Cheers!

Update: OK, thanks for all the info, I've also read in a couple of places that I can't call WaitForSingleObject() if I used _beginthread(), but if I call _endthread() in the thread shouldn't that work? What's the deal there?


Source: (StackOverflow)

How to provide user name and password when connecting to a network share

When connecting to a network share for which the current user (in my case, a network enabled service user) has no rights, name and password have to be provided.

I know how to do this with Win32 functions (the WNet* family from mpr.dll), but would like to do it with .Net (2.0) functionality.

What options are available?

Maybe some more information helps:

  • The use case is a windows service, not an Asp.Net application.
  • The service is running under an account which has no rights on the share.
  • The user account needed for the share is not known on the client side.
  • Client and server are not members of the same domain.

Source: (StackOverflow)

Find out what process registered a global hotkey? (Windows API)

As far as I've been able to find out, Windows doesn't offer an API function to tell what application has registered a global hotkey (via RegisterHotkey). I can only find out that a hotkey is registered if RegisterHotkey returns false, but not who "owns" the hotkey.

In the absence of a direct API, could there be a roundabout way? Windows maintains the handle associated with each registred hotkey - it's a little maddening that there should be no way of getting at this information.

Example of something that likely wouldn't work: send (simulate) a registered hotkey, then intercept the hotkey message Windows will send to the process that registered it. First, I don't think intercepting the message would reveal the destination window handle. Second, even if it were possible, it would be a bad thing to do, since sending hotkeys would trigger all sorts of potentially unwanted activity from various programs.

It's nothing critical, but I've seen frequent requests for such functionality, and have myself been a victim of applications that register hotkeys without even disclosing it anywhere in the UI or docs.

(Working in Delphi, and no more than an apprentice at WinAPI, please be kind.)


Source: (StackOverflow)

Where can I find my .emacs file for Emacs running on Windows?

I tried looking for the .emacs file for my Windows install for Emacs but could not find it. Does it have the same filename under Windows as in Unix? Do I have to create it myself? If so, under what specific directory does it go?


Source: (StackOverflow)

Adding external library into Qt Creator project

How can I add external library into a project built by Qt Creator RC1 (version 0.9.2)? For example, the win32 function EnumProcesses() requires Psapi.lib to be added in the project to build.


Source: (StackOverflow)