/in/foo.c: In function 'main':
/in/foo.c:10:2: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
  memset(z, 0, sizeof(z));
  ^~~~~~
/in/foo.c:10:2: warning: incompatible implicit declaration of built-in function 'memset'
/in/foo.c:10:2: note: include '<string.h>' or provide a declaration of 'memset'