Thread: pointer problems

I have two functions:
void getinfo(char *test) // test is initialised with some text
void setinfo(char *test) // the value gained from getinfo is supplied here

eg:

// first I get the information
char *info = NULL;
getinfo(&info);

// then i use the information
setinfo(info);

// the output that setinfo() gives me appears garbled
info = !@h^


this isn't the exact code, but i don't want to make the problem specific to what I'm doing. I'm assuming that there is something wrong with my syntax and not the logic?

is this totally confusing? should i paste the original code?

the code is basically trying to use libcurl to open a web page and then
after all the redirects are done, open the page that was opened last.

// this opens the page
curl_easy_setopt(curl, CURLOPT_URL, "http://www.google.com/");
curl_easy_perform(curl);

// curl_easy_getinfo() fetches the final URL and stores it in lasturl
// lasturl needs to be of type char *
char *lasturl = NULL;
curl_easy_getinfo(curl, CURLINFO_EFFECTIVE_URL, &lasturl);

// i then want to use lasturl to open the same page again
// again lasturl needs to be of type char *
curl_easy_setopt(curl, CURLINFO_URL, lasturl);
curl_easy_perform(curl);

//however the second call to curl_easy_perform() failes
//if i manually set lasturl like so
lasturl = "http://www.google.com/"
// it works correctly

hope that helps

>> lasturl needs to be of type char *

It looks like it should be a pointer to a char*, or char**. Based on a quick glance at some libcurl documentation I would think your original code for the get is correct. It sounds like the function sets the pointer to the appropriate memory containing the url. Perhaps you can cout lasturl at that point to be sure.

>> curl_easy_setopt(curl, CURLINFO_URL, lasturl);

Are you sure this isn't supposed to be CURLOPT_URL instead of CURLINFO_URL?

Ok, I rewrote everything. If you check in the code below, you'll see the output I get.

Code:

#include <iostream>
#include "curl/curl.h"

using namespace std;

int main()
{
    CURL *curl_handle;
    CURLcode result;

    curl_handle = curl_easy_init();

    curl_easy_setopt(curl_handle, CURLOPT_URL, "http://www.google.com/");
    curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, true);
    curl_easy_setopt(curl_handle, CURLOPT_FOLLOWLOCATION, true);
    curl_easy_setopt(curl_handle, CURLOPT_AUTOREFERER, true);
    curl_easy_perform(curl_handle);

    char *lasturl = NULL;
    result = curl_easy_getinfo(curl_handle, CURLINFO_EFFECTIVE_URL, &lasturl);

    /*
        here is the output:

        LastURL: http://www.google.co.nz/
        * <url> malformed
        * URL using bad/illegal format or missing URL
        * Closing connection #0
        * Closing connection #1
    */
    if ((result == CURLE_OK) && lasturl) {
        cout << "LastURL: " << lasturl << endl;

        curl_easy_setopt(curl_handle, CURLOPT_URL, lasturl);
        curl_easy_perform(curl_handle);
    }

    curl_easy_cleanup(curl_handle);
	return 0;
}

Now if I set lasturl manually, like so:

Code:

lasturl = "http://www.google.co.nz/";

It works perfectly? I still think this is a syntax issue though?

Ok, problem solved.
It appears that I needed to cpy the info held in lasturl elsewhere as it is soon destroyed by libcurl.

thanks for the help.