c – 使用mmap()时,从’void *’到’char *’的转换无效

char* filename;
unsigned long long int bytesToTransfer;
int fd,pagesize;
char *data;

fd = open(filename,O_RDONLY);
if (fd==NULL){
    fputs ("File error",stderr);
    exit (1);
}

cout << "File Open: " << filename << endl;

pagesize = getpagesize();
data = mmap((caddr_t)0,bytesToTransfer,PROT_READ,MAP_SHARED,fd,0);
if (*data == -1) {
    fputs ("Memory error",stderr);
    exit (2);
}

cout << "Data to Send: " << data << endl;

但是当我编译时,我会收到：

error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]
data = mmap((caddr_t)0,0);

有人能给我一个暗示什么是错的吗？