Hi.

Curl hangs if I return CURL_READFUNC_ABORT from readfunc callback.
 The mechanics of hang is following:

 1. my readfunc callback returns CURL_READFUNC_ABORT

 2. formdata.c:readfromfile() function has code:
    nread = form->fread_func(buffer, 1, size, form->data->line);
    if(nread > size)
      /* the read callback can return a value larger than the buffer but
         treat any such as no data in this case */
      nread = 0;
      ....
      return nread;

 So, readfromfile() casts CURL_READFUNC_ABORT to 0 and returns it.

 3. formdata.c:Curl_FormReader()
 if((form->data->type == FORM_FILE) ||
     (form->data->type == FORM_CALLBACK)) {
    gotsize = readfromfile(form, buffer, wantedsize); // <-- 0 here

    if(gotsize)
      /* If positive or -1, return. If zero, continue! */
      return gotsize; // <--
does not return
  }
  do {
           // <-- there are other fields
  .....
    gotsize += form->data->length - form->sent;
                               // <-- gotsize increased, in my case
it is 48 now
  .....
  } while(form->data && (form->data->type < FORM_CALLBACK));
  return gotsize; //
<-- gotsize = 48

 4. Curl_fillreadbuffer()
  // nread is 48 here, CURL_READFUNC_ABORT defined as 0x10000000

  nread = (int)conn->fread_func(data->req.upload_fromhere, 1,
 buffersize, conn->fread_in);
  if(nread == CURL_READFUNC_ABORT) { // <-- false
    failf(data, "operation aborted by callback");
    *nreadp = 0;
    return CURLE_ABORTED_BY_CALLBACK;
  }

  Looks as bug to me.

 ---
 WBR, Anton.
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Received on 2011-10-12