Can't get rid of LNK 2019 error in Dll - c++

Question

I keep getting link 2019 errors on this ctor,ctor-copy ctor-assignment code that works in other projects with no errors. I am trying to include it in a plain DLL generated with the MFC support option checked. I'm in VS2010.
#include "stdafx.h"
#include "Name.h"
CNameBase::CNameBase()
{
IsGlobal = false;
UseShortName = true;
m_ShortName = NO_NAME_ID ;
m_Description = "";
pMe = this;
}
CNameBase::CNameBase( const CNameBase& ref )
{
m_Description = ref.m_Description;
IsGlobal = ref.IsGlobal;
m_LongName = ref.m_LongName;
m_ShortName = ref.m_ShortName;
UseShortName = ref.UseShortName;
pMe = ref.pMe;
}
CNameBase& CNameBase::operator=( const CNameBase& ref )
{
m_Description = ref.m_Description;
IsGlobal = ref.IsGlobal;
m_LongName = ref.m_LongName;
m_ShortName = ref.m_ShortName;
UseShortName = ref.UseShortName;
pMe = ref.pMe;
return *this;
}
The link errors are:
error LNK2019: unresolved external symbol "public: __thiscall CNameBase::CNameBase(void)" (??0CNameBase##QAE#XZ) referenced in function "public: __thiscall CName::CName(void)" (??0CName##QAE#XZ)
1>clayer.obj : error LNK2019: unresolved external symbol "public: __thiscall CNameBase::CNameBase(class CNameBase const &)" (??0CNameBase##QAE#ABV0##Z) referenced in function "public: __thiscall CName::CName(class CName const &)" (??0CName##QAE#ABV0##Z)
1>clayer.obj : error LNK2019: unresolved external symbol "public: class CNameBase & __thiscall CNameBase::operator=(class CNameBase const &)" (??4CNameBase##QAEAAV0#ABV0##Z) referenced in function "public: class CName & __thiscall CName::operator=(class CName const &)" (??4CName##QAEAAV0#ABV0##Z)
1>C:\devt\hftappb\Debug\CLayer.dll : fatal error LNK1120: 3 unresolved externals
The funny thing is this code works and has worked. The Ctors do what they're supporsed to do and have been in other solution. I stick the class in this file and suddenly get these errors that I am having dififculty resolving. I've compared project settings between this project and projects I know this code works in. What else could be causing this?

Answer 1

The cpp file that holds the implementation of the 3 functions doesn't compile/link into the exe/dll.
If you're using C++ namespaces, you need to make sure that both header and cpp use it. The namespace is part of the class name.

Answer 2

Thank you all for responding to my question. The question took the better part of a day to resolve but I wanted to share the answer with others since it can happen to anyone. The solution to the problem wasn't any code, it was a configuration issue. In VS2010, apparently, ALL files that your project references must be in the list of files that appear with the project in the Solution Explorer. I am not privy to the underlying architecture so I can't answer why this is required. On the surface, there's NO reason for it. If there are files #included into a project either explicity or implicitly through the Project paths and whose functions I reference from files that are included in the Project's list of files in Solution Explorer, functions in those files should be able to reference functions in files that aren't included in the project filelist in Sol Exp.
The rules for #include and other rules are convoluted enough in C++ without MSFT adding their layers of confusion. These types of errors would be easily prevented with better error reporting and/or UI management.
The rules I've learned are this
1. Never make more than 1 copy of the same file in the entire solution. Multiple copies of the same file are hard to keep symchronized and lead to confusion as to which one is being used.
2. All files being used in a project must be listed in that project but rule 1 should be respected.
Steps (approximate)
1. Create a project
2. Create a .h and .cpp with global functions (or in a class doesn't matter)
3. In the same parent directory as project 1, create project 2 There should be two project directories underneath one parent
4. In project 2 in File Explorer, create a subfolder called Common
5. Create a .h and .cpp in that folder and create a simple function that returns a value
6. Add those files to project 2 in Solution Explorer
7. In Project 1, in the .cpp, create a function that #includes the file for project 2 and calls that function in that file.
8. The compiler generates a 2019 and 2001 unresolved external link error. What it should do is report that those files are required to be in your project's file list.