Language: C++

#include <stdio.h>
main(){
??????
????int x;
  int i = 0;
??????
????while(1)
  {
	++i;
	scanf("%d",&x);
	if( x == 0 ) break;
	printf("Case %d: %d\n", i, x);
  }
  return 0;
}

Compiler output:
a.cc:2:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    2 | main(){
      | ^~~~
a.cc: In function 'int main()':
a.cc:3:1: error: expected primary-expression before '?' token
    3 | ??????
      | ^
a.cc:3:2: error: expected primary-expression before '?' token
    3 | ??????
      |  ^
a.cc:3:3: error: expected primary-expression before '?' token
    3 | ??????
      |   ^
a.cc:3:4: error: expected primary-expression before '?' token
    3 | ??????
      |    ^
a.cc:3:5: error: expected primary-expression before '?' token
    3 | ??????
      |     ^
a.cc:3:6: error: expected primary-expression before '?' token
    3 | ??????
      |      ^
a.cc:4:1: error: expected primary-expression before '?' token
    4 | ????int x;
      | ^
a.cc:4:2: error: expected primary-expression before '?' token
    4 | ????int x;
      |  ^
a.cc:4:3: error: expected primary-expression before '?' token
    4 | ????int x;
      |   ^
a.cc:4:4: error: expected primary-expression before '?' token
    4 | ????int x;
      |    ^
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:4:5: error: expected ':' before 'int'
    4 | ????int x;
      |     ^~~
      |     :
a.cc:4:5: error: expected primary-expression before 'int'
    4 | ????int x;
      |     ^~~
a.cc:6:1: error: expected primary-expression before '?' token
    6 | ??????
      | ^
a.cc:6:2: error: expected primary-expression before '?' token
    6 | ??????
      |  ^
a.cc:6:3: error: expected primary-expression before '?' token
    6 | ??????
      |   ^
a.cc:6:4: error: expected primary-expression before '?' token
    6 | ??????
      |    ^
a.cc:6:5: error: expected primary-expression before '?' token
    6 | ??????
      |     ^
a.cc:6:6: error: expected primary-expression before '?' token
    6 | ??????
      |      ^
a.cc:7:1: error: expected primary-expression before '?' token
    7 | ????while(1)
      | ^
a.cc:7:2: error: expected primary-expression before '?' token
    7 | ????while(1)
      |  ^
a.cc:7:3: error: expected primary-expression before '?' token
    7 | ????while(1)
      |   ^
a.cc:7:4: error: expected primary-expression before '?' token
    7 | ????while(1)
      |    ^
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1)
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1)
      |     ^~~~~