Can the main() function call itself in C ?

Recursion in main() Function: An Unexpected Compiler Behavior

Calls to the main() function are generally not allowed in C . However, in practice, it may be possible on some platforms, particularly on Linux systems with the g compiler. Let's delve into how this behavior is achieved.

In the provided code example:

<code class="cpp">#include <iostream>
#include <cstdlib>

int main() {
    cout << "!!!Hello World!!!" << endl;
    system("pause");
    return main();
}</code>

The call to main() within the main() function allows for an endless loop. However, this is not standard C behavior.

Compiler Magic or Undefined Behavior?

Is it possible to obtain the current running function using a magic variable or macro? No, there is no such provision in the C Standard.

Linux Compiler Exception

Despite the Standard's prohibition, the Linux g compiler compiles code with main() calls within main() without raising errors. This is due to the compiler's lenient interpretation of the C Standard.

Practical Demonstration

Consider the following code:

<code class="cpp">#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{
    int y = rand() % 10; // returns 3, then 6, then 7
    cout << "y = " << y << endl;
    return (y == 7) ? 0 : main();
}</code>

When compiled with g , this code generates assembly code that looks like:

<code class="assembly">main:
        ...
        cmpl    , -12(%rbp)
        je      .L7
        call    main
        ...
.L7:
        ...
        leave
        ret</code>

In this assembly code, main is called just like any other function. The call to main() in the main() function is translated into a regular function call.

Conclusion

While calling main() from within main() is not allowed by the C Standard, it may be possible to do so on certain platforms with specific compilers that tolerate such behavior. However, it is important to emphasize that this is not standard C and may lead to unexpected results in different environments or versions of compilers.

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