Server.c Non-existant file and cat.exe question

Question

I'm almost done with parse function, but I get 301 Moved Permanently error in the above mentioned cases. I am aware that .exe is not present in our lookup function, but shouldn't we return NULL in that case? Also, I saw that staff wrote lines to handle these two cases. In my test file, everything works, so I really have no clue what I am doing wrong.

Any idea what might the problem be, please?

Thanks!

EDIT: As always, I didn't post my code. I kind of avoid it, although I am aware that you couldn't tell anything without it. :)

Here's my parse function:

bool parse(const char* line, char* abs_path, char* query)
{

char* first_space = strchr(line, ' ');
char* second_space = strrchr(line, ' ');
int l_line = strlen(line);
int l_method = l_line - strlen(first_space);
int l_request = l_line - l_method - strlen(second_space) - 1;

char request[l_request + 1];
char method[l_method + 1];

// copy request and method into its arrays
strncpy(request, first_space + 1, l_request);
strncpy(method, line, l_method);

request[l_request] = '\0';
method[l_method] = '\0';

// check for method
if (strcmp(method, "GET") != 0)
{
    error(405);
    return false;
}

// check for both spaces
if (first_space == NULL || second_space == NULL)
{
    error(405);
    return false;
}

// make sure the beggining of the request is ok
if (request[0] != '/')
{
    error(501);
    return false;
}

// we dun want no quotations marks
for (int i = 0, n = strlen(request); i <= n; i++)
{
    if (request[i] == '"')
    {
        error(400);
        return false;
    }
}

char* compare = strstr(line, "HTTP/1.1");
if (compare == 0)
{
    error(505);
    return false;
}

// makin' room for version
char* copy_version = malloc(sizeof(10));
strncpy(copy_version, compare, strlen(compare) - 2);

// query - what to do and not do if there's ? or not
char* q_mark = strchr(request, '?');
if (q_mark != NULL)
{
    if (strcmp(q_mark + 1, "") == 0)
    {
        query = malloc(sizeof(LimitRequestLine + 1));
        query[0] = '\0';
        abs_path = malloc(sizeof(LimitRequestLine + 1));
        strncpy(abs_path, request, strlen(request) + strlen(q_mark));

    }    

    else if (q_mark + 1 != NULL)   
    {
        query = malloc(sizeof(LimitRequestLine + 1));
        strcpy(query, q_mark);
        abs_path = malloc(sizeof(LimitRequestLine + 1));
        strncpy(abs_path, request, strlen(request) - strlen(query));
    }
}

else if (q_mark == NULL)
{
    query = malloc(sizeof(LimitRequestLine + 1));
    query[0] = '\0';
    abs_path = malloc(sizeof(LimitRequestLine + 1));
    strncpy(abs_path, request, strlen(request));
}

return true;
}

I would like to add that before I implemented query, I had all green smileys (except for the last one, which was "TODO"), and although I did not change a thing, later I got these three red ones. Now, when I run check50 server2, the only thing that's wrong is the last line - which means I did not implement indexes well, but I think I know how to do it properly. What bugs me, is the check50 server1.

Answer 1

This is bad abs_path = malloc(sizeof(LimitRequestLine + 1)); (and query too). Remember, parse receives a pointer to abs_path, which is already allocated on the stack (implicitly) in main. The malloc gives it a new address on the heap. The strncpy updates the contents at that (new) address. But back in main it will be looking for abs_path at the "original" address, the contents of which have not been updated. If I'm understanding properly, it works sometimes (eg /cat.jpg) and not others (eg /cat.exe). Frankly, I'm a little confused by that, and I would say it is due to the vagaries of memory on the stack and the heap. You might consider adding some printfs in parse and after you return from parse. Something like

printf("contents....%s<-\n",abs_path);
printf("pointer  %p\n",abs_path);`

would illustrate.