error LNK2005: new and delete already defined in LIBCMTD.lib(new.obj)

I have a Visual studio 2005 solution that has two projects. One is a static library and the other is a executable used to test the features in the static library. The static library uses MFC. I got the following errors when I built the solution.

uafxcwd.lib(afxmem.obj) : error LNK2005: "void * __cdecl operator new(unsigned int)" (??2@YAPAXI@Z) already defined in LIBCMTD.lib(new.obj)
uafxcwd.lib(afxmem.obj) : error LNK2005: "void __cdecl operator delete(void *)" (??    3@YAXPAX@Z) already defined in LIBCMTD.lib(dbgdel.obj)
uafxcwd.lib(afxmem.obj) : error LNK2005: "void * __cdecl operator new[](unsigned int)" (??_U@YAPAXI@Z) already defined in libcpmtd.lib(newaop.obj)
uafxcwd.lib(afxmem.obj) : error LNK2005: "void __cdecl operator delete[](void *)" (??_V@YAXPAX@Z) already defined in LIBCMTD.lib(delete2.obj)

I do not know how to overcome this. Can some one please explain why this error is occuring. Any explanation that gives an overview of .lib files linkage will be highly appreciated.

ali

The CRT libraries use weak external linkage for the new, delete, and DllMain functions. The MFC libraries also contain new, delete, and DllMain functions. These functions require the MFC libraries to be linked before the CRT library is linked. http://support.microsoft.com/kb/148652

Solution based on VS2005 (Replace Nafxcwd.lib with Uafxcwd.lib for ~VS2013)

go to project>properties>configuration properties>linker>input

add to "Additional dependency" -> Nafxcwd.lib Libcmtd.lib

add to "ignore specific library" -> Nafxcwd.lib;Libcmtd.lib

order of libraries is important( Nafxcwd.lib;Libcmtd.lib).

One thing to try is to make sure you have:

#include "stdafx.h"

as the first line in your .cpp files. I'm sure that's not the answer in all cases, but it made the identical error go away in my case.

in config linker input

In additional dependicies put uafxcw.lib;LIBCMT.lib
In Ignore specific put put uafxcw.lib;LIBCMT.lib

be sure that you have #include <afx.h> in "stdafx.h" BEFORE other includes like #include <string>

I meet this problem in a MFC solution of Visual Studio 2010, while changing Use MFC in a Shared DLL into Use MFC in a Static Library in Project -> Properties -> Configuration Properties -> General.

I solve the problem by the following ways, please locate Project -> Properties -> Configuration Properties -> Linker -> Input at first.

In Debug mode:

Add uafxcwd.lib;Libcmtd.lib in Additional Dependencies.
Add uafxcwd.lib;Libcmtd.lib in Ignore Specific Default Libraries.

In Release mode:

Add uafxcw.lib;Libcmt.lib in Additional Dependencies.
Add uafxcw.lib;Libcmt.lib in Ignore Specific Default Libraries.

Notice:

Don't miss the ; between the two .lib files.
A suffix -d must be added in the files in Debug mode.

Make sure the C++ runtime library that you are linking with is the same on your static library as well as your executable. Check your project properties C/C++->Code generation->runtime library settings.

Typo. One stupid way you got that is instead of include the header, you inlucde the cpp. e.g.

#include <myclass.cpp> //should be #include <myClass.h>

First, libcmtd.lib is for a debug version and libcmt.lib is for production. Double-check that you're not including both. One place to check is the "Command Line" section of the Configuration Properties/Linker project properties.

If you go to the properties for the project, and open up the Configuration Properties/Linker/Input section, you can "Ingore Specific Library"...try listing libcmtd.lib in that field.

For me, I have a static library compiled with _CRTDBG_MAP_ALLOC, and the application not compiled with _CRTDBG_MAP_ALLOC, I was receiving then LNK2005. I've changed the application to compile with _CRTDBG_MAP_ALLOC, and the LNK2005 disappear.

евгений соснин

Got rid of the problem

uafxcwd.lib(afxmem.obj) : warning LNK4006: "void * __cdecl operator new(unsigned __int64)"

In additional dependicies put uafxcw.lib.
In Ignore specific put put uafxcw.lib.

Check the manifest file of both projects, make sure that they are linking the same version of the standard library. Most likely they are not, check the properties->code generation->standard library linking.

I also had a similar problem. The link given by Donnie explains the the reason. The solution was to look at the error messages and then removing those libs involved and adding those libs in the order of MFC libs first and then CRT libs.

The way to do that in vs2008 is given by ali.

I will also add that if you have replaced the new/delete operators (and if so, please do the array and the scalar both), you may need to tag them as __forceinline so that the obj doesn't collide with the lib.

For example, I did these to force aligned allocations and had the same trouble until I did that:

__forceinline void * operator new(size_t size)
{
    return _aligned_malloc(size, 16);
}
__forceinline void operator delete(void* ptr)
{
    _aligned_free(ptr);
}
__forceinline void * operator new [](size_t size)
{
    return _aligned_malloc(size, 16);
}
__forceinline void operator delete [](void* ptr)
{
    _aligned_free(ptr);
}

A header file declared and defined a variable. Possible solutions include: Declare the variable in .h: extern BOOL MyBool; and then assign to it in a .c or .cpp file: BOOL MyBool = FALSE;. Declare the variable static. Declare the variable selectany.

https://msdn.microsoft.com/en-us/library/72zdcz6f.aspx

For me the problem was solved by changing

Project -> Properties -> Configuration Properties -> General: Use of MFC = Use MFC in a Shared DLL

Before it was set to "Use Standard Windows Libraries"

Additionally I had to set the /MD option under

Project -> Properties -> C/C++ -> Code Generation : Runtime Library = Multi-threaded DLL (/MD)

I had created two fresh projects with VS2017, one was working the other not, so I compared what was the difference. The one working was created with
File > New Project > Visual C++ > MFC/ATL > MFC Application
the one not working was created with
File > New Project > Visual C++ > Windows Desktop > Windows Desktop Wizard
then adding MFC. In both cases I was using MFC as static lib. I had figured out two fixes. But before that we have to add imports because the second project had NONE!

#include <afxwin.h>         // MFC core and standard components
#include <afxext.h>         // MFC extensions
#include <afxdisp.h>        // MFC Automation classes

Now either of the two fixes worked for me:

Project > Properties > Configuration Properties > General > Use of MFC set it to use in a Shared DLL, this should also automatically set C/C++ > Code Generation > Runtime Library to Multi-threaded debug dll /MDd make sure it indeed did that. Try compile now, for me it worked.
I noticed the working project had some imports in stdafx.h, I copied them into pch.h in the other project, it worked.(Keeping the properties unchanged, so static lib was used). The code copied was this:

#define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS      // some CString constructors will be explicit

// turns off MFC's hiding of some common and often safely ignored warning messages
#define _AFX_ALL_WARNINGS
#include <afxwin.h>         // MFC core and standard components
#include <afxext.h>         // MFC extensions


#include <afxdisp.h>        // MFC Automation classes

The other solutions changing Linker settings I tried them but they did not work.
I would appreciate if somebody knows why my solution works, it is weird, why including those headers in pch.h solves a linker issue whereas including those same headers anywhere else triggers that error??

来源：https://stackoverflow.com/questions/1146338/error-lnk2005-new-and-delete-already-defined-in-libcmtd-libnew-obj

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