Why am I getting the 'Error LNK2019 unresolved external symbol _main' in my C application?

Error: Resolving External Symbols in C Applications

Problem:

When building a C application, you may encounter the following error:

Error LNK2019 unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)

Cause:

This error typically arises when the following conditions are not met:

• The project's entry point function main() is not defined or is not accessible from the main module.
• The linker cannot locate the definition of main() in the specified library.

Solution:

To resolve this issue, follow these steps:

1. Ensure the Existence of main() Function:

Verify that your project includes a function called main() in the source code. This function serves as the entry point for the program and must be defined as follows:

int main(int argc, char** argv)
{
    // Your program logic goes here
    return 0;
}

2. Linker Settings:

Check your project's linker settings to ensure that the main() function is accessible from the main module. In Visual Studio, go to:

• Project Properties
• Linker
• System
• Under Subsystem, select Windows

3. Verify Library Inclusion:

Confirm that the library containing the definition of main() is included in the project's linker settings. This can be found in:

• Project Properties
• Linker
• Input
• Additional Dependencies

Example Project:

#include "windows.h"

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance, LPSTR lpcmdline, int ncmdshow)
{
    MessageBox(NULL, _T("Hello, world!"), _T("My Application"), MB_OK);

    return 0;
}

Note: In this example, main() is declared using the WINAPI macro because the WinMain() function is the entry point for Windows applications.

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