How to handle the error "LNK2019 unresolved external symbol" in visual studio 2022

Question

How to handle the error "LNK2019 unresolved external symbol" in visual studio 2022

Blaise Xiangyun Deng 20

ERROR CODE

The code is from Chapter 12, Programming Solving with C++, Tenth Edition, a programming example given by the author. I am not sure if I have done something wrong with Visual Studio settings.

Background: I'm using VS code with Visual Studio 2022

To help me resolve this issue, could you please guide me on what could be the potential causes of this error and how to fix it? Thank you.

Viorel 122.6K Reputation points

2023-07-09T19:45:38.4666667+00:00

As an intermediate solution, try adding #include <dtime.cpp> to the end of 12-08.cpp.

Or use Visual Studio with C++ workload, and create a Console application.

Probably Visual Studio Code needs some additional attention.
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T01:42:15.43+00:00

By adding #include "dtime.cpp" to the end of 12-08.cpp. the question is solved. However it breaks the rule of ADT since I have to quote the implementation source.
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T01:44:13.5633333+00:00

By adding #include "dtime.cpp" to the end of 12-08.cpp. the question is solved. However it breaks the rule of ADT. since I have to quote implementation source.
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-07-10T02:25:32.5+00:00

Can you share the source code without private information via GitHub?
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T03:14:12.18+00:00

https://github.com/Kotokowa/given-example-dtime
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T03:36:13.1633333+00:00

https://github.com/Kotokowa/given-example-dtime

Accepted answer

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Viorel 122.6K Reputation points

2023-07-09T19:45:38.4666667+00:00

As an intermediate solution, try adding #include <dtime.cpp> to the end of 12-08.cpp.

Or use Visual Studio with C++ workload, and create a Console application.

Probably Visual Studio Code needs some additional attention.
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T01:42:15.43+00:00

By adding #include "dtime.cpp" to the end of 12-08.cpp. the question is solved. However it breaks the rule of ADT since I have to quote the implementation source.
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T01:44:13.5633333+00:00

By adding #include "dtime.cpp" to the end of 12-08.cpp. the question is solved. However it breaks the rule of ADT. since I have to quote implementation source.
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-07-10T02:25:32.5+00:00

Can you share the source code without private information via GitHub?
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T03:14:12.18+00:00

https://github.com/Kotokowa/given-example-dtime
Blaise Xiangyun Deng 20 Reputation points

2023-07-10T03:36:13.1633333+00:00

https://github.com/Kotokowa/given-example-dtime

Answer 1

Hi, @Blaise Xiangyun Deng

The code works fine in Visual Studio. (Remove #include <dtime.cpp> in the last line of 12-08.cpp)

Create an empty project and add .h/.cpp files to the project.
User's image

enter image description here

Since your error is generated in Visual Studio Code (which is different from Visual Studio). Please try to compile your code in Visual Studio. (Do not forget to install C++ workload in Visual Studio Installer)
For problems about Visual Studio Code, you could ask for help on GitHub.

Best regards,

Minxin Yu

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Answer 2

RLWA32 49,636

The linker error messages indicate that the linker has not been provided the implementation of the DigitalTime class.

It appears from the image posted that the source file dtime.cpp has not been compiled (I assume that is the implementation). If it has, perhaps the resultant dtime.obj file has not been specified as a linker input.

Blaise Xiangyun Deng 20 Reputation points

2023-07-09T14:51:21.11+00:00

I'm sorry that I'm new to C++ that my questions may seem naive. However when I try to compile dtime.cpp it failed with fatal error LNK1561 "entry point must be defined" for implementation does not include function main(). I wonder how I can deal with the question. I highly appreciate your help.
RLWA32 49,636 Reputation points

2023-07-09T15:20:21.1666667+00:00

Did you read the documentation at Linker Tools Error LNK1561 and review the possible causes in the context of your own situation?

Since we've only seen a small snippet of one of the source files my best guess is that the executable program requires both dtime.obj and 12-08.obj. The dtime.cpp source file is not intended to be a complete implementation for any executable.

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How to handle the error "LNK2019 unresolved external symbol" in visual studio 2022

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