/in/foo.cc: In function 'void mul(long long int*, long long int (*)[2])':
/in/foo.cc:12:20: warning: 'sizeof' on array function parameter 'f' will return size of 'long long int*' [-Wsizeof-array-argument]
  memcpy(f,c,sizeof f);
                    ^
/in/foo.cc:6:17: note: declared here
 void mul(int f[2],int a[2][2])
                 ^
/in/foo.cc:12:20: warning: argument to 'sizeof' in 'void* memcpy(void*, const void*, size_t)' call is the same expression as the destination; did you mean to dereference it? [-Wsizeof-pointer-memaccess]
  memcpy(f,c,sizeof f);
                    ^
/in/foo.cc: In function 'void mulself(long long int (*)[2])':
/in/foo.cc:22:20: warning: 'sizeof' on array function parameter 'a' will return size of 'long long int (*)[2]' [-Wsizeof-array-argument]
  memcpy(a,c,sizeof a);
                    ^
/in/foo.cc:15:24: note: declared here
 void mulself(int a[2][2])
                        ^
/in/foo.cc:22:20: warning: argument to 'sizeof' in 'void* memcpy(void*, const void*, size_t)' call is the same expression as the destination; did you mean to dereference it? [-Wsizeof-pointer-memaccess]
  memcpy(a,c,sizeof a);
                    ^