Small nitpick. Functions in C that take no arguments are written name(void){...} not name(){...}. This latter form is an old-style definition which doesn't introduce a prototype into the scope.

For functions that have prototypes, it is okay, but when they do not, you're losing type checking (yes, even on the number of arguments).

The following program compiles with no diagnostics for me with -W -Wall -ansi -pedantic, with GCC 7.3 on Ubuntu 18:

  int func()
  {
    return 0;
  }

  int main()
  {
    func(3);
    return 0;
  }

-std=c11 (as you're using) makes no difference.

The same is not true of C++: func() in C++ is a prototype definition. C++ supports (void) for compatibility with C, but even in nonsensical contexts: class::class(void);