../confuse.c:118:15: error: use of undeclared identifier 'str'
siz = strlen(str) + 1;
^
../confuse.c:123:15: error: use of undeclared identifier 'str'
memcpy(copy, str, siz);

The fix could be either change the parameter to 'str' or change usage of 'str' in the function body to 's'.