Include libcurl to Microsoft Visual Studio 2015

问题:

I don't have any idea how to include curl to my project. I've read this Getting LibCurl to work with Visual Studio 2013, but in my folder with curl (from https://curl.haxx.se/download.html#Win64 - Win64 x86_64 7zip) is only libcurl.dll in bin folder. In lib folder there is only libcurl.a and libcurldll.a.

I've added include path to VC++ Directories -> Inlcude Directories, and try to compile this code:

#include <stdio.h>
#include <curl/curl.h>
#include <string.h>
#include <stdlib.h>

struct url_data {
    size_t size;
    char* data;
};

size_t write_data(void *ptr, size_t size, size_t nmemb, struct url_data *data) {
    size_t index = data->size;
    size_t n = (size * nmemb);
    char* tmp;

    data->size += (size * nmemb);

#ifdef DEBUG
    fprintf(stderr, "data at %p size=%ld nmemb=%ld\n", ptr, size, nmemb);
#endif
    tmp = realloc(data->data, data->size + 1); /* +1 for '\0' */

    if(tmp) {
        data->data = tmp;
    } else {
        if(data->data) {
            free(data->data);
        }
        fprintf(stderr, "Failed to allocate memory.\n");
        return 0;
    }

    memcpy((data->data + index), ptr, n);
    data->data[data->size] = '\0';

    return size * nmemb;
}

char *handle_url(char* url) {
    CURL *curl;

    struct url_data data;
    data.size = 0;
    data.data = malloc(4096); /* reasonable size initial buffer */
    if(NULL == data.data) {
        fprintf(stderr, "Failed to allocate memory.\n");
        return NULL;
    }

    data.data[0] = '\0';

    CURLcode res;

    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &data);
        res = curl_easy_perform(curl);
        if(res != CURLE_OK) {
                fprintf(stderr, "curl_easy_perform() failed: %s\n",  
                        curl_easy_strerror(res));
        }

        curl_easy_cleanup(curl);

    }
    return data.data;
}

int main(int argc, char* argv[]) {
    char* data;

    if(argc < 2) {
        fprintf(stderr, "Must provide URL to fetch.\n");
        return 1;
    }
    data = handle_url(argv[1]);

    if(data) {
        printf("%s\n", data);
        free(data);
    }

    return 0;
}

but i get errors like this:

unresolved external symbol __imp_curl_easy_strerror referenced in function handle_url

回答1:

You have to link your application against a libcurl.a (for static linking) or libcurldll.a (for dynamic linking).

First you should add an additional library directory in a project settings that points to a folder that contains these .a files and after that there are two options:

To add a dependency in a project settings...

Project Properties -> Linker -> Input -> Additional Dependencies.

...or to use a preprocessor (just add this line of code to a source file):

#pragma comment(lib, "libcurl.a")

Good luck!