OpenGL tutorial error MSVCTRD.lib(exe_winmain.obj): LNK2019

Willard 45

Attempting to follow a tutorial on opengl, but running into

MSVCRTD.lib(exe_winmain.obj) : error LNK2019: unresolved external symbol WinMain referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)

The tutorial simply wants to link the necessary files before proceeding (and is linked below) and tests it. I have looked for similar problems which mention setting sub systems to windows, but the problem persists and I haven't found anything to explain what the error is aside from being a linking error.

https://learnopengl.com/Getting-started/Creating-a-window

I have also attempted to remake the project in visual studio with "windows desktop application" but same result. I learned most of C++ and went straight to this so my knowledge of visual studio or opengl is limited.

RLWA32 40,756 Reputation points

2023-03-21T00:21:57.3833333+00:00

The described linker error can result from code that uses main() as the program entry point instead of WinMain().

Without seeing the actual code it is difficult to make an exact determination of the problem.
Willard 45 Reputation points

2023-03-21T06:28:17.42+00:00

@RLWA32 sorry forgot to mention that there is no code. The only thing I can suspect are either the header files or seperate .c file that it wanted to be included/added to the project. I'll check it tomorrow and share what I found.
Willard 45 Reputation points

2023-03-21T22:43:59.8233333+00:00

I have went through all the header files and glad.c file and found nothing that the error is mentioning. I made a new Visual Studio project and simply changed the subsystem to windows with no code and the same error still pops up. I even found someone saying the linking in Visual Studio 2022 is somehow worse than 2019 as it is causing problems with linking.
RLWA32 40,756 Reputation points

2023-03-21T23:11:00.77+00:00

The link to https://learnopengl.com/Getting-started/Creating-a-window contains some general instructions and speaks to GLFW and GLAD.

Since I don't know exactly what steps you have or have not performed there's not much that I can do to reliably reproduce your environment and observed issue.
Willard 45 Reputation points

2023-03-22T04:03:38.26+00:00

@RLWA32 I went through the entire page until it says "Hitting the compile button shouldn't give you any errors, at which point we're set to go for the next chapter where we'll discuss how we can actually use GLFW and GLAD to configure an OpenGL context and spawn a window."

I downloaded glfw and followed its steps to get and place the glfw3.lib file into the library directory, then added glad with KHR, glad and glad.c files for the include directory (with glad.c being added into the project instead). It should do as he says and give no errors and I attempted to add code from the next chapter with more errors pointing to being unable to load glad files. Either way thank you for trying to help.
Paul Normington 0 Reputation points

2024-03-23T22:43:35.3266667+00:00

If you're following the LearnOpenGL tutorial, I would recommend continuing to the "Hello Window" page immediately.

My project was searching desperately for a cpp file to run which is why this flagged up as an issue.

Before, there was no entry point so I think VS was getting confused, because on finishing the Hello Window, no errors and it ran as expected.

1 answer

Willard 45 Reputation points

2023-03-22T05:23:44.6133333+00:00

After some tampering with a later tutorial I simply added

int WinMain() { return 0;}

to the source code and all errors regarding LNK2019 are gone. I suspect the error will show if there is no WinMain or main (depending on subsystem) within the source.cpp for the compiler to look at. This did not occur in VS2019, but regardless thank you @RLWA32 for helping.
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1 person found this answer helpful.
Pouria 5 Reputation points

2023-05-18T04:53:20.4+00:00

This is the correct solution. If your SubSystem is set to Console, which is the default, simply create a normal main function:
int main()

{

return 0;

}

RLWA32 40,756 Reputation points

2023-05-18T11:22:29.2433333+00:00

@Pouria,

If your SubSystem is set to Console, which is the default...

A project's Linker->System-> SubSystem property is set depending on what kind of project has been created.

Perhaps you mean that a new Empty Project is created with the SubSystem property set to Console?
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