Multiple definition of main()

Question

Hi guys trying to use two main() and getting this error multiple definition of main(). I renamed my main functions then why is this error and also first defined here for my prin

Answer 1

The macro substitution of onemain and twomain occurs before the compiler proper sees the program, so that doesn't make a difference. The functions are both named main.

C++ allows different functions with the same name, but does not allow two definitions of the exact same function signature. There would be no way to form a function call expression that would reach either overload. Additionally, the functions are the same entity, and one thing cannot have two definitions.

In addition, in C++ main cannot be overloaded, because the program is supposed to start when the unique main function is called, and any given system detects what format of main the particular program uses, out of a variety of allowed formats. (This auto-detection feature also applies to C.)

But you are not asking about C++; in C, without function overloading, there are no redefinitions of the same name, even for different signatures. Each name of extern linkage in C uniquely identifies an entity, so you cannot have two.

It's unclear what you want the resulting program to do. Most likely you need to build two separate programs.