libcurl specifying the header - c++

Question

I am currently using pre-compiled minGW32 libraries for libcurl-7.21.6, C++, QT libraries, minGW32 windows compiler (in QT creator) and QT creator as my IDE.
I am trying to post some http information but keep running into a problem. I need to remove Expect: 100... from my header. From everything i have seen online,
headerlist = curl_slist_append(headerlist, "Expect:");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);
should do it, but it seems to get nullified by:
curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
If i call the HTTPPOST before the HTTPHEADER, it seems like the HTTPHEADER nullifies everything from the HTTPPOST, and vice versa.
Am I doing something wrong? Should the Expect: be somehow included in the HTTPPOST instead of separately in HTTPHEADER?
I am trying to get rid of the Expect header because the server keeps responding to my request with Expectation Failed.
Here is the curl command used with curl.exe to do the samething i'm trying to do with libcurl:
system("curl --referer http://192.168.16.23/upthefile.html -F uploadfile=#instructions.xml -F config=on http://192.168.16.23/cgi-bin/upload.cgi -H \"Expect:\">nul");
Any help will be appreciated.

Answer 1

Using cURL 7.25.0 and this snippet:
curl_global_init(CURL_GLOBAL_ALL);
struct curl_httppost *formpost = NULL;
struct curl_httppost *lastptr = NULL;
struct curl_slist *headerlist = curl_slist_append(NULL, "Expect:");
curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "field", CURLFORM_COPYCONTENTS, "value", CURLFORM_END);
CURL *curl = curl_easy_init();
if (curl)
{
curl_easy_setopt(curl, CURLOPT_URL, "http://www.example.com/");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);
curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
CURLcode res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
curl_formfree(formpost);
curl_slist_free_all(headerlist);
}
I obtain the following request (Wireshark'd):
POST / HTTP/1.1
Host: www.example.com
Accept: */*
Content-Length: 145
Content-Type: multipart/form-data; boundary=----------------------------523d686b5061
------------------------------523d686b5061
Content-Disposition: form-data; name="field"
value
------------------------------523d686b5061--
While omitting the line curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist); the header contains also:
HTTP/1.1 100 Continue