View Compilation Error

0_0_17419385_57.cpp: In function 'Bin_Tree* parse_buf(ssize_t, ssize_t, Bin_Tree*, Bin_Tree*)':
0_0_17419385_57.cpp:52:29: error: invalid conversion from 'void*' to 'Bin_Tree*' [-fpermissive]
   root = malloc(sizeof *root);
                             ^
0_0_17419385_57.cpp:57:18: error: 'isalpha' was not declared in this scope
    if (isalpha(ch) || isdigit(ch) || ch == '_')
                  ^
0_0_17419385_57.cpp:57:33: error: 'isdigit' was not declared in this scope
    if (isalpha(ch) || isdigit(ch) || ch == '_')
                                 ^