链接报错：
错误 33 error LNK2005: _DllMain@12 已经在 MSVCRTD.lib(dllmain.obj) 中定义 E:\客户问题\w_王鹏\EventLibTest_TibrvAlternative_MultiEnv-4-0.3将 DTSSysEvent.xml做为单独参数传给每个环境\EventLibTest_TibrvAlternative_MultiEnv\Win32 \APPFL\EventLibMultiEnvDLL\mfcs100d.lib(dllmodul.obj) EventLibMultiEnvDLL (Visual Studio 2010)
解决方法：
项目-》属性-》配置属性-》C/C++/预处理器，去掉预处理器定义中的_USRDLL 即可
另外：
常见预处理器设置的意义：
http://blog.csdn.net/honker110/article/details/6120810
常见的编译参数VC建立项目时总会定义"Win32"。控制台程序会定义"_CONSOLE"，否则会定义"_WINDOWS"。Debug版定义"_DEBUG"，Release版定义"NDEBUG"
与MFC DLL有关的编译常数包括：
_WINDLL 表示要做一个用到MFC的DLL
_USRDLL 表示做一个用户DLL（相对MFC扩展DLL而言）
_AFXDLL 表示使用MFC动态链接库的 regular DLL
_AFXEXT 表示要做一个MFC扩展DLL
所以：
Regular, statically linked to MFC _WINDLL,_USRDLL
Regular, using the shared MFC DLL _WINDLL,_USRDLL,_AFXDLL
Extension DLL _WINDLL,_AFXDLL,_AFXEXT
Building Your DLL
When compiling regular DLLs that statically link to MFC, the
symbols "_USRDLL" and "_WINDLL" must be defined. Your DLL code must also
be compiled with the following compiler switches:
•/D_WINDLL signifies the compilation is for a DLL
•/D_USRDLL specifies you are building a regular DLL
When compiling regularDLLs that statically link to MFC, the symbols
"_USR DLL" and"_WINDLL" must be defined. Your DLL code must also be
compile dwith the following compiler switches:
When compiling regular DLLs that dynamicallylink to MFC, you must
define t he above symbols and use the above compilerswitches.
Additionally, the sy mbol "_AFXDLL" must be definedand your DLL code
must be compiled with:
•/D_AFXDLL specifies that you are building a regular DLL that dynamicall y links to MFC
The interfaces (APIs) between the application and the DLL must
beexplicitlyexported. It is recommended that you define your interfaces
to be lowbandw idth, sticking to C interfaces where possible. More
direct C interfaces areeasi er to maintain than more
complex C++ classes.
Place your APIs in aseparate header that can be included by both C
and C++files (that way you won‘tlimit your DLL customers to C++
programmers). Se e the header ScreenCap.h in theMFC Advanced Concepts
sample DLLScreen Cap for an example. To export yourfunctions,
enter them in theEXPORTSs ection of your moduledefinition file (.DEF)
or include__declspec(dllexpor t)on yourfunction definitions.
Use__declspec(dllimport)to import thesefunctions into the client
executable.
You must add theAFX_MANAGE_STATEmacro at the beginning of all the e
xportedfunctions in regular DLLs that dynamically link to MFC to set
the curr ent modulestate to the one for the DLL. This is done by adding
the followingline of codeto the beginning of
functions exported from the DLL:
AFX_MANAGE_STATE(AfxGetStaticModuleState( ))
WinMain->DllMain
The MFC library defines the standard Win32DllMain entry point that
initializ es yourCWinAppderived object as in a normal MFC application.
Placeall DLL-specific initialization in theInitInstancememberfunction as
in a normal MFC application.
经验证可行
转自 http://blog.csdn.net/tian_jinping/article/details/14168919
或使用如下方法，是的mfc库先于msvcrtd.lib链接
_DllMain@12 已经在 MSVCRTD.lib(dllmain.obj) 中定义
VC2005解决办法：
1）Debug版本：
项目-属性-链接器-输入：忽略特定库中输入mfc80d.lib;mfcs80d.lib
项目-属性-链接器-附加依赖项：mfc80d.lib;mfcs80d.lib
就可以保证mfc80d和mfcs80d先于MSVCRTD.lib链接，OK，成功
2)Release版本
与Debug版本不同在于mfc80.lib;mfcs80.lib
