/in/foo.c: In function 'main':
/in/foo.c:5:1: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
 memset(c,sizeof(c),0);
 ^~~~~~
/in/foo.c:5:1: warning: incompatible implicit declaration of built-in function 'memset'
/in/foo.c:5:1: note: include '<string.h>' or provide a declaration of 'memset'
/in/foo.c:5:1: warning: 'memset' used with constant zero length parameter; this could be due to transposed parameters [-Wmemset-transposed-args]