错误 LNK2005 DllMain 已在 uafxcw.lib(dllmodul.obj) 中定义

Question

I have dll project. I added to my solution other quite big project that I want to use as a lib in my dll. But when I started to use new project from my dll project, I had several linking errors, also like in this question error LNK2005: new and delete already defined in LIBCMTD.lib(new.obj)

I've put into "Additional dependency" and "ignore specific library" uafxcwd.lib;Libcmtd.lib, and errors about new, delete etc now is gone, but I still got the error about DllMain.

I've also tried to put

extern "C" { int __afxForceUSRDLL; }

line to the cpp with DllMain and got additional error

Error   LNK2005 __afxForceUSRDLL already defined in dllmain.obj 

I'm completely at a loss

Answer 1

According to the Doc: Linker Tools Error LNK2005

If two objects define the same symbol, you get exactly this linker error. I suggest you could try to find out which of both libraries you actually need and then tell the linker not to use the other one.

And I suggest you should check the the linker order.The MFC libs need get linked first, and then the CRT libs could be linked.

For more details I suggest you could refer to the link: error LNK2005: _DllMain@12 already defined in MSVCRT.lib

Answer 2

I had the exact same problem with a need to use my own DllMain, but it being already defined in a library that I also needed:

error LNK2005: DllMain already defined in uafxcw.lib(dllmodul.obj)

The fix from @Jeaninez to add

#ifdef _X86_ extern "C" 
  int _afxForceUSRDLL;  
#else 
  extern "C" { int __afxForceUSRDLL; } 
#endif

just before my own DllMain worked perfectly. Thanks.