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Libcurl: Is there a problem combining CURLOPT_POSTFIELDS with CURLOPT_MIMEPOST?

From: kent williams via curl-users <>
Date: Tue, 5 Jan 2021 14:19:49 -0600

This is an interesting thing. I've been asked add posting mime files to
our usual post data.  But the two options seem to conflict.

    void do_post(char *url, char *postdata, char *imagefilename) {
          CURL *chand = curl_easy_init();
          const long
          curl_easy_setopt(chand, CURLOPT_PROTOCOLS,protocols);
          curl_easy_setopt(chand, CURLOPT_NOPROGRESS, 1L);
          curl_easy_setopt(chand, CURLOPT_ERRORBUFFER, errbuf);
          curl_easy_setopt(chand, CURLOPT_URL, url.chars());
          curl_easy_setopt(chand, CURLOPT_NOSIGNAL, 1);
          curl_easy_setopt(chand, CURLOPT_POSTFIELDS, postdata);
          curl_easy_setopt(chand, CURLOPT_POSTFIELDSIZE, postdata.length());
          // set the postdata
          curl_easy_setopt(chand, CURLOPT_POSTFIELDS, postdata); //
    name=value pairs with & separating
          curl_easy_setopt(chand, CURLOPT_POSTFIELDSIZE, strlen(postdata);
          // set the mime file upload
               curl_mime *mime1(nullptr);
               curl_mimepart *part1(nullptr);
           // create a mime handle
           mime1 = curl_mime_init(chand);
           // get the part for the file
           part1 = curl_mime_addpart(mime1);
           // assign filename to part
           curl_mime_filedata(part1, imagefilename);
           curl_mime_name(part1, "image");
           curl_easy_setopt(chand, CURLOPT_MIMEPOST, mime1);
           int curlfailed = curl_easy_perform(chand);
           return curlfailed;

What seems to be happening is that if you use CURLOPT_MIMEPOST, the
CURLOPT_POSTFIELDS are forgotten.  You can do the former, or the latter
but not both.

Is there a way this can happen -- i.e. add a file (i.e. an image file,

Received on 2021-01-05