Is `main()` Really the First Code Executed in a C Program?

Is Main() Truly the Initiation of a C Program?

The C Standard defines main() as the exclusive starting point of a program: "A program shall contain a global function called main, which is the designated start of the program."

However, the code below seems to contradict this definition:

int square(int i) { return i*i; }
int user_main()
{ 
    for ( int i = 0 ; i < 10 ; ++i )
           std::cout << square(i) << endl;
    return 0;
}
int main_ret= user_main();
int main() 
{
        return main_ret;
}

Surprisingly, this code executes the user_main() function before entering main(), which is supposed to be the initial execution point. Moreover, the code compiles without errors or warnings.

Defining the 'Start' of a Program

It's crucial to interpret the term "start of the program" correctly. The Standard defines the start as the point where the program is considered to begin, not necessarily when the first code executes.

In this example, the program starts with main(), but that does not imply that no code executes beforehand. In reality, substantial code is typically executed before main(), especially during initialization.

Standard Compliance

Despite the code's unusual order of execution, it fully adheres to the Standard. According to the definition, the start of the program is main(), even though user_main() executes earlier. The order of execution does not alter the fact that the program's inception is defined as the main() function.

Therefore, the given code is Standard-compliant, and it does not invalidate the Standard's definition of the start of the program as main().

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