CURLcode Curl_http_done(struct connectdata *conn,
                        CURLcode status, bool premature)
{
  struct Curl_easy *data = conn->data;
  struct HTTP *http = data->req.protop;

  infof(data, "Curl_http_done: called premature == %d\n", premature);

  Curl_unencode_cleanup(conn);

#ifdef USE_SPNEGO
  if(data->state.proxyneg.state == GSS_AUTHSENT ||
     data->state.negotiate.state == GSS_AUTHSENT) {
    /* add forbid re-use if http-code != 401/407 as a WA only needed for
     * 401/407 that signal auth failure (empty) otherwise state will be RECV
     * with current code.
     * Do not close CONNECT_ONLY connections. */
    if((data->req.httpcode != 401) && (data->req.httpcode != 407) && // <-- uncommenting this
       !data->set.connect_only) // <-- uncommenting this
      streamclose(conn, "Negotiate transfer completed"); // <-- uncommenting this
    Curl_cleanup_negotiate(data);
  }
#endif
...

#define CURL_STATICLIB
#include <curl/curl.h>

//
// Select one of the test cases:
//

// #1 Negotiate upload with CURLOPT_UPLOAD (which I expect to be working)

#define TEST_NEGOTIATE
#define TEST_UPLOAD

// ------------------------------------------------

// #2 Negotiate upload with CURLOPT_POSTFIELDS (works)
/*
#define TEST_NEGOTIATE
#define TEST_POSTFIELDS
*/
// ------------------------------------------------

// #3 NTLM upload (works)
/*
#define TEST_NTLM
#define TEST_UPLOAD
*/
// ------------------------------------------------

// #4 Negotiate GET and UPLOAD with same handle
// (after successful GET the connection is killed, PUT fails)
/*
#define TEST_NEGOTIATE
#define TEST_GET_WITH_UPLOAD
*/
// ------------------------------------------------


static int CURLdebugfunction(CURL *, curl_infotype infotype, char *str, size_t len, void *)
{
  const char *infostring = "CURLINFO_???";
  switch (infotype) {
  #define ENTRY(NAME) case NAME: infostring = TEXT(#NAME); break;
    ENTRY(CURLINFO_TEXT)
      ENTRY(CURLINFO_HEADER_IN)
      ENTRY(CURLINFO_HEADER_OUT)
      ENTRY(CURLINFO_DATA_IN)
      ENTRY(CURLINFO_DATA_OUT)
    #undef ENTRY
  }
  printf("CURLDEBUGINFO %s: %*.*s\n",
    (const char *)infostring, (int)len, (int)len, (const char *)str);
  return 0;
}
size_t CURLheaderfunction(void *ptr, size_t size, size_t nmemb, void *stream)
{
  char *hdr = (char *)malloc(size*nmemb + 1);
  if (hdr) {
    memcpy(hdr, ptr, size*nmemb);
    hdr[size*nmemb] = '\0';
    printf("RECEIVED HEADER: %s", (const char *)hdr);
    free(hdr);
  }
  else {
    printf("HEADER: OUT OF MEMORY\n");
  }
  return size*nmemb;
}
static size_t CURLreadpos = 0;
size_t CURLreadfunction(void *ptr, size_t size, size_t nmemb, void *stream)
{
  size_t read = 0;
  for (; CURLreadpos < 10 && CURLreadpos < size * nmemb; CURLreadpos++) {
    ((char *)ptr)[CURLreadpos] = 'a';
    read++;
  }
  printf("READ REQUEST DATA: %llu -> %llu\n", size*nmemb, (UINT64)read);
  return read;
}
int CURLseekfunction(void *ptr, curl_off_t offset, int origin)
{
  printf("SEEK: %lld, %d\n", (INT64)offset, origin);
  if (origin == SEEK_SET) {
    CURLreadpos = offset;
    return CURL_SEEKFUNC_OK;
  }
  printf("SEEK: NOT IMPL\n");
  return CURL_SEEKFUNC_CANTSEEK;
}
int main(void)
{
  CURL *curl;
  CURLcode res;
  curl_global_init(CURL_GLOBAL_ALL);
  curl = curl_easy_init();
  if (curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://url-to-server-with-windows-auth-goes-here");
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, CURLheaderfunction);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, CURLreadfunction);
    curl_easy_setopt(curl, CURLOPT_SEEKFUNCTION, CURLseekfunction);
    curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, CURLdebugfunction);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

  #if defined(TEST_NEGOTIATE)
    curl_easy_setopt(curl, CURLOPT_HTTPAUTH, CURLAUTH_NEGOTIATE);
    curl_easy_setopt(curl, CURLOPT_USERNAME, "");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "");
  #endif
  #if defined(TEST_NTLM)
    curl_easy_setopt(curl, CURLOPT_HTTPAUTH, CURLAUTH_NTLM);
    curl_easy_setopt(curl, CURLOPT_USERNAME, "<NTLM-User>");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "<NTLM-Password>");
  #endif

  #if defined(TEST_UPLOAD)
      curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
      curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
      curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, 10);
  #endif
  #if defined(TEST_POSTFIELDS)
    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "aaaaaaaaaa");
  #endif
  #if defined(TEST_GET_WITH_UPLOAD)
    curl_easy_setopt(curl, CURLOPT_HTTPGET, 1L);
  #endif

    res = curl_easy_perform(curl);

  #if defined(TEST_GET_WITH_UPLOAD)
    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, 10);
    res = curl_easy_perform(curl);
  #endif

    if (res != CURLE_OK) {
      printf("curl_easy_perform() failed: %s\n",
        curl_easy_strerror(res));
    }
    else {
      long http_code = 0;
      curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
      printf("CURL STATUS: %ld\n", http_code);
    }
    curl_easy_cleanup(curl);
  }
  curl_global_cleanup();
  return 0;
}