Cppcon 2014 (The C++ Conference) September 7th – 12th Bellevue, WA, USA: schedule has been posted

A lot of readers have been curious about what conferences I attend.  I’ve attended many PDCs, C++ (going native), builds, MVP summits, and TechEd’s in the past.   I’ve even hit a couple of consumer electronics shows and Comdexes (I’m dating myself here) in the past.

A big new conference is being held this year in Bellevue, Washington, USA this year that looks pretty exciting.  The schedule of talks has been posted now at

http://cppcon.org/conference-program/

and the list of talks looks amazing.   There are well over a 100 talks going on.

Registration is still open at

http://cppcon.org/registration/

How to target XP with VC2012 or VC2013 and continue to use the Windows 8.x SDK

One of the limitations of the Microsoft provided solution for targeting XP while using Visual Studio 2012 (Update 1 and above), or Visual Studio 2013, is that you must use a special “Platform toolset” in project properties that forces usage of the Windows SDK 7.1 (instead of Windows 8.x SDK which is the default).  The other function the platform toolset provides is that it sets the Linker’s “Minimum Required Version” setting to 5.01 (instead of 6 which is the default).  But that function can just as easily be done manually by setting it in project properties.

So how about the first main function of the platform toolset?   Setting the platform toolset to one that targets XP does the following:

(1) Changes the Platform SDK being used from Windows SDK 8.x (8.1 with VC2013 and 8.0 with VC2012) back to Windows SDK 7.1

(2) Adds a preprocessor define:  _USING_V110_SDK71_ to the build

The second one turns out to be important, due to a piece of code in atlwinverapi.h, namely the following:


extern inline BOOL __cdecl _AtlInitializeCriticalSectionEx(__out LPCRITICAL_SECTION lpCriticalSection, __in DWORD dwSpinCount, __in DWORD Flags)
{
#if (NTDDI_VERSION >= NTDDI_VISTA) && !defined(_USING_V110_SDK71_) && !defined(_ATL_XP_TARGETING)
     // InitializeCriticalSectionEx is available in Vista or later, desktop or store apps
     return ::InitializeCriticalSectionEx(lpCriticalSection, dwSpinCount, Flags);
#else
     UNREFERENCED_PARAMETER(Flags);
     // ...otherwise fall back to using InitializeCriticalSectionAndSpinCount.
     return ::InitializeCriticalSectionAndSpinCount(lpCriticalSection, dwSpinCount);
#endif

As you can see, if we do not use the platform toolset that defines _USING_V110_SDK71, i.e we don’t use the Windows SDK 7.1, then we don’t get the benefit of avoiding a call to InitializeCriticalSectionEx, which is a function only available on Vista and above.  This will cause your binary to not load on XP.

But what if we really want to use the Windows 8.x SDK (taking care, of course, that we don’t call any Windows 8.x functions directly, to keep support for older operating systems). Why would we want this? For example, we may want a structure definition, some preprocessor define, or function declaration, i.e. we may want to support some feature of Windows 8.x if actually running our app on that OS.

Say we’ve decided to use Windows 8.x SDK while still allowing our app to run on XP. Are there any options available? i.e. can you keep using the v110/v120 toolsets instead of the v110_xp/v120_xp toolsets? Yes, it turns out that Microsoft left a nice loophole in the code to do exactly that. Notice the mysterious define in the block of code above named _ATL_XP_TARGETING. Turns out this is an alternative way to support XP targeting while _USING_V110_SDK71_ is NOT defined. So if you really want to support XP while using Windows 8.x SDK, we simply need to ensure our code is built with _ATL_XP_TARGETING defined. The easiest way to do this is to add a /D_ATL_XP_TARGETING flag to our C/C++ command line options in project properties.

Then, the only other step is to set the “Minimum Required Version” in project properties under Linker – System to 5.01, and we’re all set - a simple way to target XP and still use the Windows 8.1 SDK without using the platform toolset that Microsoft provided to target XP.

In summary, the _ATL_XP_TARGETING define, while undocumented, is an interesting way to keep support for XP while also allowing continued use of the Windows 8.x SDK (rather than being forced to be permanently stuck on  the older Windows 7.1 SDK)

Visual Studio 2013 support for targeting Windows 8

I’ve been working my way through the multitude of //build 2013 session videos on channel9, and I came across an interesting presentation:

Upgrading Windows 8 Apps to Windows 8.1

There is a lot of really great information about the gotchas for deciding on making an app that is specific to Windows 8.1.

The main point you need to remember: once you make your app target Windows 8.1 (e.g. by converting to an 8.1 app and taking advantage of 8.1 specific APIs), your app will not run on Windows 8.  On the other hand, if you target Windows 8, your app will run under both Windows 8 and Windows 8.1

Here’s the kicker: Visual Studio 2013 will NOT support creation of new Windows 8 store apps, you’ll only be able to create Windows 8.1 store apps.   However you will be able to edit and build existing Windows 8 projects with Visual Studio 2013.

So if you want to continue to target Windows 8 when creating new store apps, you are going to need both Visual Studio 2012 and Visual Studio 2013 installed. You’ll really only need Visual Studio 2012 to create the project, and once it’s created you can switch over to Visual Studio 2013.

This seems to me to not be a technical limitation, but more of a way to encourage developers to target Windows 8.1 from the get go if creating a new app.

To me it would make more sense to support creating Windows 8 store apps in Visual Studio 2013, since the infrastructure is already there to continue to edit and build existing Windows 8 projects.

Going Native 2013 C++ conference – new discount for first 50 people!

The Going Native 2013 conference is taking place this September 4-6, 2013 in Bellevue, Washington.

50 lucky people can register now for Going Native 2013 – Use promo code: $100dGN13 to receive a US$100 discount.

Note: this code may cease to work at any time, once the 50 spots are filled, it goes back to the regular price.

I personally can’t wait for this conference, the first one last year was quite special, and they’ve extended it this year for one extra day.

Why MUIRCT is so cool (aka separating Win32 resources into satellite DLLs, the easy way)

MUIRCT is a utility that Microsoft made available starting with the Windows Vista SDK.  It’s a localization utility that allows you to “split” resources from a DLL that has already been built.

Let’s give an example.  You have a large legacy app with dozens of DLLs, all using the model of code+resources in the same module.  After all, up to this point there has been really no good techniques within Visual Studio itself to use the satellite DLL approach, without doing a lot of manual work.  Things like creating dialog boxes, etc are simply easier to do with the built in wizards (class wizards, event handlers, etc) if the code and the resources reside in the same EXE/DLL.  Unfortunately this is the exact opposite of what we need from a translation/localization perspective.    The satellite DLL approach allows you to keep your code and your resources separate, but it involves a lot of manual work, especially if you have a complex app with many EXEs and DLLs.

What if there was a way to continue with the old style code+resources in the same module approach during development, but then separate out the resources after the fact, and require only minor changes to your code?  How is that possible?  When you load a resource from a handle (e.g. let’s say your app is test.exe, and you pass in the HINSTANCE of test to LoadString, how does the operating system know to look elsewhere for the resources?  A single handle can’t represent two separate modules behind the scenes can it?

Turns out, in Vista and higher, MUIRCT can separate these resources for you, and the operating system will load them automatically when you do a resource load.  And you have control at the individual resource level as to what is treated as language neutral (what stays in test.exe) and what is localizable (what goes into the satellite DLL)

Example:

Create a new MFC app, test.exe using all the defaults

Compile the app, then run the following on the output:

muirct -q test.rcconfig test.exe test2.exe test2.exe.mui

The above commmand splits up the app test.exe into two components, a language neutral part (the EXE) and a DLL named test.exe.mui which contains the localized parts. Now translating this test.exe.mui using a resource editor, your code is separate from your resources.

Then you would store for example your app in two folders:

test2.exe en-us\test2.exe.mui

When you run your app, the operating system knows to look for your resources in en-us folder (or what ever your ultimate fallback language is selected to be)

So if you have a bug fix to test.exe, you don’t need to redo all the languages because the resources and the code are separate.

I’ve only just scratched the surface on this topic, there are many more technical details you’ll need to learn, fortunately this whole process (including a full example of an rcconfig file) is provided by Microsoft in a walkthrough and sample code here:

http://archive.msdn.microsoft.com/hellomui

and

http://archive.msdn.microsoft.com/MUIIzer

Note: this approach works in Vista and higher.  if you need XP support, you’ll need much more extensive changes to your application as there is no support for this technique at the OS level, so you end up writing a lot of extra code, which makes the whole thing pointless.  So I would recommend only using this if you are able to drop XP support from your list of supported operating systems.

Finding the kernel32.dll module handle in a Windows Store app using approved APIs

As there are a lot of forbidden Win32 APIs in Windows Store apps (i.e. APIs that, if you call them, will cause your app to fail app certification), there are often other alternative APIs that you have to call instead.  For example, the CreateFile API is banned, but for Windows Store apps they made CreateFile2.

But what about if I wanted to get the module handle of a DLL? Specifically of kernel32?  Well, looking at the help for GetModuleHandle we see the unfortunate info:

Minimum supported client Windows XP [desktop apps only]

So we can only use this with desktop apps.  For your own packaged libraries you can use LoadPackagedLibrary API.  But this doesn’t work for system DLLs.  So how can you the the handle to kernel32.dll, for example, by using only approved store APIs?

This is where VirtualQuery comes in.  Interestingly, the API’s help page lists the following info:

Minimum supported client Windows XP [desktop apps | Windows Store apps]

This is great news, because VirtualQuery can get you the module handle of any DLL just by querying any particular known function in the DLL you want the handle to.

I discovered this trick a while ago – previously I used it to find the module handle of the DLL any code is being called from.  See:

http://www.codeguru.com/cpp/w-p/dll/tips/article.php/c3635/Tip-Detecting-a-HMODULEHINSTANCE-Handle-Within-the-Module-Youre-Running-In.htm

You probably know where I’m going here, but VirtualQuery itself is a function exported from kernel32.dll!

So all we need to do to get the module handle of kernel32.dll is to do a VirtualQuery of VirtualQuery:

HMODULE GetKernelModule()
{
    MEMORY_BASIC_INFORMATION mbi = {0};
    VirtualQuery( VirtualQuery, &mbi, sizeof(mbi) );
    return reinterpret_cast<HMODULE>(mbi.AllocationBase);
}

And then from your own code:

HMODULE kernelHandle = GetKernelModule();

You can now pass this into functions such as GetProcAddress (which is also approved).  As you can see, we have a powerful way to get the module handles of any particular DLL that we have in our process address space, and then use that to get function pointers to any particular function.

Note you should only use this technique on approved APIs in Windows Store apps.   But for debugging purposes (and just to have some fun), it might be cool to do something like the following:

Generate a blank XAML (C++ Windows Store) app, add a button to the blank form. Double click on the button. Add this code in place of the event handler:


typedef int (WINAPI *pMessageBox)( __in_opt HWND hWnd,
  __in_opt LPCTSTR lpText, __in_opt LPCTSTR lpCaption, __in UINT uType);

typedef HWND (WINAPI *pGetActiveWindow)(void);

typedef HMODULE (WINAPI *pGetModuleHandle)(__in_opt LPCTSTR lpModuleName);

void App1::MainPage::Button_Click_1(Platform::Object^ sender,
  Windows::UI::Xaml::RoutedEventArgs^ e)
{
 static pMessageBox MessageBox_p = 0;
 static pGetActiveWindow GetActiveWindow_p = 0;
 static pGetModuleHandle GetModuleHandle_p = 0;

 HMODULE kmod = GetKernelModule();

 GetModuleHandle_p = (pGetModuleHandle)GetProcAddress(kmod, "GetModuleHandleW");

 HMODULE mod = GetModuleHandle_p(L"user32.dll");

 MessageBox_p = (pMessageBox)GetProcAddress(mod, "MessageBoxW");
 GetActiveWindow_p = (pGetActiveWindow)GetProcAddress(mod, "GetActiveWindow");

 MessageBox_p(GetActiveWindow_p(), L"Hello", L"Hello", MB_OK);
}

Build and deploy your app, run it, and the press the button and see what happens.  Something you don’t ever want to do in a production app :)

How do my API wrapper functions avoid triggering linker errors?

Now that we have a stable (VS2012+Update 3) solution for XP support, there is no longer a need for these wrappers.

I was going to make a general write-up on how all of my API wrapper classes work, but in searching around, I found out that Antony, who graciously contributed the x64 version of the xpsupport wrappers, already wrote up an excellent article a while back describing how the linker resolves symbols.  Please read:

http://blog.macrium.com/2012/05/upgrading-to-vnext-yet-supporting-windows-xp/

Thanks to Antony for his contributions to this project and his great description.

So using assembly allows us to avoid the dreaded “duplicate symbol” error, if we had tried to do this in C/C++.   Interestingly, GCC has a much more elegant way of doing this:

http://sourceforge.net/p/mingw-w64/code/HEAD/tree/trunk/mingw-w64-libraries/winstorecompat/src/GetTickCount.c

notice the last line (edited to avoid use of a macro):

DWORD (WINAPI *__imp_GetTickCount)(void) asm(“__imp__GetTickCount@0″) = GetTickCount;

The asm keyword can be used to define a symbol that can be overridden by an arbitrary symbol.  This functionality is not available in MSVC.

I’ll be talking more about wrappers in the near future, specifically in the area of forbidden Win32 APIs in Windows Store apps.