/in/foo.c: In function 'zhi':
/in/foo.c:4:11: warning: unused variable 'j' [-Wunused-variable]
     int i,j;
           ^
/in/foo.c: In function 'main':
/in/foo.c:22:9: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
         memset(b,0,sizeof(b));
         ^~~~~~
/in/foo.c:22:9: warning: incompatible implicit declaration of built-in function 'memset'
/in/foo.c:22:9: note: include '<string.h>' or provide a declaration of 'memset'
/in/foo.c:23:11: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
         l=strlen(a);
           ^~~~~~
/in/foo.c:23:11: warning: incompatible implicit declaration of built-in function 'strlen'
/in/foo.c:23:11: note: include '<string.h>' or provide a declaration of 'strlen'