The antivirus swears at "Hello world". False alarm?

Question

C++ / C#

I decided to study the C language. Initial data - Win7 64 bit, Avast antivirus, MinGW compiler.
There are two versions of the self-written Halloweenworld:
1.

#include <stdio.h>
int main() {
  printf("Hello world!\n");
  return 0;	
}

2.

#include <stdio.h>
void main() {
  printf("Hello world!\n");
}

When you run the first option, Avast detects Win64:Malware-gen, when you compile and run the second, everything goes fine. I would like to know if these are some tricks of Avast or is my computer really infected?

Answer 1

Avast will swear at all self-compiled programs.

Answer 2

I think it's a false positive heuristic. As it used to be for all antiviruses with programs written in Borland 6. Of course, there is a possibility that you downloaded some kind of left mingw from somewhere, which inserts malicious code into the program. But this is unlikely. Just in case, send the file to https://www.virustotal.com/