atlbase.h and different versions of VC CRT

Question

I have a C++/CLI project created with Visual Studio 2010 that targets .NET Framework 3.5 and PlatformToolset v90. Initially it requests the VC CRT of version 9.0.21022.8, but if I include atlbase.h header then it requests the VC CRT of version 9.0.30729.6161. Why does this happen? And how can I make it to target 9.0.30729.6161 without including atlbase.h?

I tried to define macroses _BIND_TO_CURRENT_CRT_VERSION=1 and _BIND_TO_CURRENT_VCLIBS_VERSION=1 but this didn't help.

Answer 1

The version is set by vc/include/crtassem.h, near the bottom you can see:

#ifndef _CRT_ASSEMBLY_VERSION
#if _BIND_TO_CURRENT_CRT_VERSION
#define _CRT_ASSEMBLY_VERSION "9.0.30729.6161"
#else
#define _CRT_ASSEMBLY_VERSION "9.0.21022.8"
#endif
#endif

So the rule is that you can explicitly override the version by #defining _CRT_ASSEMBLY_VERSION. Don't do that. As you noted in your question, #defining _BIND_TO_CURRENT_CRT_VERSION to 1 gets you the version string you want.

Having a problem with this in a C++/CLI project is possible. You can compile C++/CLI code without ever #including any of the CRT include files. So you'll end up with a default version which, ironically, is defaulted by the linker to its own version of the CRT. So a workaround is to explicitly put #include <crtassem.h> in one of your source code files. #including atlbase.h would do that too since it does include CRT headers but of course is the big hammer approach.

Additional troubleshooting is available from Project + Properties, C/C++, Advanced, Show Includes = Yes. You'll see a trace of all the #include files getting included in the Output window.

Beware that you'll now have the additional burden to ensure that the up-to-date version of msvcr90.dll gets deployed on the user's machine. Your program will fail to start if it is missing or old.