How to fix error LNK2001 & LNK2019

0
votes

ProjectAAA.obj : error LNK2001: unresolved external symbol "public: __thiscall X::ClassEvent::ClassEvent(unsigned int)" (??0ClassEvent@X@@QAE@I@Z)

boost::shared_ptr<ClassEvent> bcfEvent(new ClassEvent((unsigned int) 10));

I have defined ClassEvent::ClassEvent(unsigned int) and have no idea how to fix this LINK errors.

Any suggestion is appreciated.

Thank you

MORE INFO:

1>ProjectAAA.obj : error LNK2019: unresolved external symbol "public: __thiscall APP::X::ClassEvent::ClassEvent(unsigned int)" (??0ClassEvent@X@APP@@QAE@I@Z) referenced in function "private: class std::vector,class std::allocator > > __thiscall APP::X::ProjectAAA::GenerateEvents(class std::map > > const &)" (?GenerateEvents@ProjectAAA@X@APP@@AAE?AV?$vector@V?$shared_ptr@VClassEvent@X@APP@@@boost@@V?$allocator@V?$shared_ptr@VClassEvent@X@APP@@@boost@@@std@@@std@@ABV?$map@VDate@APP@@IUEventAttributesMapCompare@ProjectAAA@X@2@V?$allocator@U?$pair@$$CBVDate@APP@@I@std@@@std@@@5@@Z)

Now I have completely isolated the error:

1>ProjectAAA.obj : error LNK2019: unresolved external symbol "public: __thiscall APP::X::ClassEvent::ClassEvent(unsigned int)" (??0ClassEvent@X@APP@@QAE@I@Z) referenced in function "private: void __thiscall APP::X::ProjectAAA::TestGenerateEvents(void)" (?TestGenerateEvents@ProjectAAA@X@APP@@AAEXXZ)

3
c++boost
Might be helpful: stackoverflow.com/questions/12573816/… – chris
Need more information. Show a minimal but complete example that produces this error message. – John Dibling
simple code works fine. I have a huge project and I am not able to use any functions defined in the class of ClassEvent. Compilation is fine but link always gives errors. – q0987
Make sure there is only one file named ClassEvent.cpp in the whole project. If this is not the case, the generated obj files will collide and thus symbols will be missing. – Karel Petranek
Did you implement your ClassEvent::ClassEvent(unsigned int) inside namespace X? It doesn't seem to ba nested inside APP::X according to the error message. – Dietmar Kühl

3 Answers

1
votes

Your problem is having two ClassEvent.cpp files in your solution. When VC++ compiles your solution, it outputs all obj files in one directory and thus generates two ClassEvent.obj files. Whichever cpp is compiled later overwrites the former. This causes symbols from the first one being lost and invisible to the linker.

You can fix this issues by opening properties of one of the files, choosing C/C++ -> Output Files -> Object File Name and changing it to some non-colliding value (such as ClassEvent2.obj).

I believe this is a bug in Visual Studio but it hasn't been addressed in last 4 versions and is therefore likely to stay.

1
votes

After multiple testing, I found the solution.

Someone in the team excludes the ClassEvent.CPP from the project!!!

0
votes

In my case all begun working correctly after I changed the build architecture from x64 to x86 bit. Two days ago I had the same problem. This was caused by deploying my program to another computer. For some reason, which I don't know, the architecture settings have changed from x86 (as I write) to x64. PS. I used Visual Studio 2015;