主要内部的功能声明和C中的外部主要功能

Question

The first program compiled properly.second gave error saying too few argument for foo... is global declaration ignored by the compiler in both programs?

first program:

#include<stdio.h>
    void foo();
int main()
{
  void foo(int);
  foo(1);
  return 0;
}

void foo(int i)
{
   printf("2 ");
}

void f()
{
   foo(1);
}

second program:

void foo();
int main()
{
  void foo(int);
  foo();
  return 0;
}

void foo()
{
   printf("2 ");
}

void f()
{
   foo();
}

Answer 1

The inner declaration hides declarations at the global scope . The second program fails because the declaration void foo(int); hides the global declaration void foo(); ; so when you say foo within main you are referring to the one taking an int as argument.

Answer 2

I see that you investigate the specific behavior of inner declaration but why not:

#include<stdio.h>

void foo(int);

int main()
{
    foo(1);
    return 0;
}

void foo(int i)
{
   printf("2 ");
}

void f()
{
   foo(1);
}

or even:

#include<stdio.h>

void foo(int i)
{
   printf("2 ");
}

void f()
{
   foo(1);
}

int main()
{
    foo(1);
    return 0;
}