If you give a *_LARGE option you MUST make sure that the type of the passed-in

argument is a curl_off_t. If you use CURLOPT_INFILESIZE (without _LARGE) you
must make sure that to pass in a type 'long' argument. */

docs/examples/ftpupload.c

@@ -78,8 +78,12 @@ int main(int argc, char **argv)
        DLL may not use the variable's memory when passed in to it from an app
        like this. */
 
-    /* and give the size of the upload (optional) */
-    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, file_info.st_size);
+    /* Set the size of the file to upload (optional).  If you give a *_LARGE
+       option you MUST make sure that the type of the passed-in argument is a
+       curl_off_t. If you use CURLOPT_INFILESIZE (without _LARGE) you must
+       make sure that to pass in a type 'long' argument. */
+    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
+                     (curl_off_t)file_info.st_size);
 
     /* Now run off and do what you've been told! */
     res = curl_easy_perform(curl);