Why Am I Getting the 'Error LNK2019 unresolved external symbol _main' in My C Program?

<h2>Error: Unresolved External Symbol _main</h2>

In programming, it's common to encounter the error "Error LNK2019 unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)". This error arises when the compiler cannot find the definition of the main function, which is the entry point of a C program.

<h3>Understanding the Error Message</h3>

The error message indicates that:

• The linker is unable to resolve the reference to an external symbol named "_main".
• This symbol is referenced in a function called "invoke_main".

<h3>Cause of the Error</h3>

Typically, this error occurs when the main function is not defined or is not properly declared with the appropriate function prototype.

<h3>Solution</h3>

To resolve this error, ensure the following:

• Define the main function in your code: In a C program, the main function must be defined as follows:

int main() {
  // Your code here
}

• Check your project properties: In Visual Studio, verify that the following project property setting is set correctly:

  • Project Properties->Linker->System->SubSystem = Windows

This setting instructs the linker to generate a Windows executable, which requires a main function.

<h3>Example Code</h3>

For reference, here's a complete example code that includes a working main function:

#include <iostream>

int main() {
  std::cout << "Hello, world!" << std::endl;
  return 0;
}

By following these steps, you should be able to resolve the "Error LNK2019 unresolved external symbol _main" issue and successfully build your C program.

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