Language: C

i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}

Compiler output:
main.c:1:1: warning: data definition has no type or storage class
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      | ^
main.c:1:1: error: type defaults to 'int' in declaration of 'i' [-Wimplicit-int]
main.c:1:3: error: type defaults to 'int' in declaration of 'n' [-Wimplicit-int]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |   ^
main.c:1:5: error: type defaults to 'int' in declaration of 't' [-Wimplicit-int]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |     ^
main.c:1:7: error: return type defaults to 'int' [-Wimplicit-int]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |       ^~~~
main.c: In function 'main':
main.c:1:7: error: type of 'm' defaults to 'int' [-Wimplicit-int]
main.c:1:20: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |                    ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
main.c:1:20: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |                    ^~~~~
main.c:1:20: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:41: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |                                         ^~~~~~
main.c:1:41: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:41: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:1:41: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:64: error: 'INT_MIN' undeclared (first use in this function)
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |                                                                ^~~~~~~
main.c:1:1: note: 'INT_MIN' is defined in header '<limits.h>'; this is probably fixable by adding '#include <limits.h>'
  +++ |+#include <limits.h>
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
main.c:1:64: note: each undeclared identifier is reported only once for each function it appears in
    1 | i,n,t;main(m){for(;scanf("%d",&n,t=0),n;printf("%d\n",m))for(m=INT_MIN;n--&&scanf("%d",&i);(t+=i)>m?m=t:(t<0)&&(t=0));}
      |                                                                ^~~~~~~