Language: C

#define s scanf("%d",&b)
c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}

Compiler output:
main.c:2:1: warning: data definition has no type or storage class
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      | ^
main.c:2:1: error: type defaults to 'int' in declaration of 'c' [-Wimplicit-int]
main.c:2:8: error: return type defaults to 'int' [-Wimplicit-int]
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |        ^~~~
main.c: In function 'main':
main.c:2:8: error: type of 'a' defaults to 'int' [-Wimplicit-int]
main.c:2:8: error: type of 'b' defaults to 'int' [-Wimplicit-int]
main.c:1:11: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | #define s scanf("%d",&b)
      |           ^~~~~
main.c:2:22: note: in expansion of macro 's'
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                      ^
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | #define s scanf("%d",&b)
main.c:1:11: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | #define s scanf("%d",&b)
      |           ^~~~~
main.c:2:22: note: in expansion of macro 's'
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                      ^
main.c:1:11: note: include '<stdio.h>' or provide a declaration of 'scanf'
    1 | #define s scanf("%d",&b)
      |           ^~~~~
main.c:2:22: note: in expansion of macro 's'
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                      ^
main.c:1:11: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | #define s scanf("%d",&b)
      |           ^~~~~
main.c:2:45: note: in expansion of macro 's'
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                             ^
main.c:1:11: note: include '<stdio.h>' or provide a declaration of 'scanf'
    1 | #define s scanf("%d",&b)
      |           ^~~~~
main.c:2:45: note: in expansion of macro 's'
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                             ^
main.c:2:51: error: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                                   ^~~~
main.c:1:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
  +++ |+#include <stdlib.h>
    1 | #define s scanf("%d",&b)
main.c:2:51: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                                   ^~~~
main.c:2:51: note: include '<stdlib.h>' or provide a declaration of 'exit'
main.c:2:57: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                                         ^~~~~~
main.c:2:57: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:2:57: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:2:57: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:2:47: error: void value not ignored as it ought to be
    2 | c[999];main(a,b){for(s,a=b;a--;c[b]=1)s;for(s;~s?:exit(!printf("%d\n",++a));a+=c[b]);}
      |                                               ^