/in/foo.cc: In function 'void convert(char*, int*)':
/in/foo.cc:9:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<strlen(s);i++)a[i]=s[i]-48;
             ~^~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:43:5: warning: unused variable 'i' [-Wunused-variable]
 int i,j,k,len,w;
     ^
/in/foo.cc:43:7: warning: unused variable 'j' [-Wunused-variable]
 int i,j,k,len,w;
       ^
/in/foo.cc:43:9: warning: unused variable 'k' [-Wunused-variable]
 int i,j,k,len,w;
         ^
/in/foo.cc:43:15: warning: unused variable 'w' [-Wunused-variable]
 int i,j,k,len,w;
               ^
/in/foo.cc: In function 'int cheng(int*, int*, int, int)':
/in/foo.cc:31:9: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
 return i+j-2;
        ~^~