diff --git a/lib/cookie.c b/lib/cookie.c
index 5a8e4fc65..fd7341f0b 100644
--- a/lib/cookie.c
+++ b/lib/cookie.c
@@ -250,9 +250,9 @@ static const char *get_top_domain(const char * const domain, size_t *outlen)
   len = strlen(domain);
   last = memrchr(domain, '.', len);
   if(last) {
-    first = memrchr(domain, '.', (size_t) (last - domain));
+    first = memrchr(domain, '.', (last - domain));
     if(first)
-      len -= (size_t) (++first - domain);
+      len -= (++first - domain);
   }
 
   if(outlen)
@@ -717,9 +717,9 @@ Curl_cookie_add(struct Curl_easy *data,
       if(!queryp)
         endslash = strrchr(path, '/');
       else
-        endslash = memrchr(path, '/', (size_t)(queryp - path));
+        endslash = memrchr(path, '/', (queryp - path));
       if(endslash) {
-        size_t pathlen = (size_t)(endslash-path + 1); /* include end slash */
+        size_t pathlen = (endslash-path + 1); /* include end slash */
         co->path = malloc(pathlen + 1); /* one extra for the zero byte */
         if(co->path) {
           memcpy(co->path, path, pathlen);
diff --git a/lib/dict.c b/lib/dict.c
index c26d6d34c..408d57b92 100644
--- a/lib/dict.c
+++ b/lib/dict.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -101,7 +101,7 @@ static char *unescape_word(struct Curl_easy *data, const char *inputbuff)
   if(!newp || result)
     return NULL;
 
-  dictp = malloc(((size_t)len)*2 + 1); /* add one for terminating zero */
+  dictp = malloc(len*2 + 1); /* add one for terminating zero */
   if(dictp) {
     char *ptr;
     char ch;
diff --git a/lib/file.c b/lib/file.c
index 77fcf2536..e50e98876 100644
--- a/lib/file.c
+++ b/lib/file.c
@@ -306,7 +306,7 @@ static CURLcode file_upload(struct connectdata *conn)
   while(!result) {
     size_t nread;
     size_t nwrite;
-    int readcount;
+    size_t readcount;
     result = Curl_fillreadbuffer(conn, (int)data->set.buffer_size, &readcount);
     if(result)
       break;
@@ -314,7 +314,7 @@ static CURLcode file_upload(struct connectdata *conn)
     if(readcount <= 0)  /* fix questionable compare error. curlvms */
       break;
 
-    nread = (size_t)readcount;
+    nread = readcount;
 
     /*skip bytes before resume point*/
     if(data->state.resume_from) {
diff --git a/lib/gopher.c b/lib/gopher.c
index d65049969..3ecee9bdc 100644
--- a/lib/gopher.c
+++ b/lib/gopher.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -89,7 +89,7 @@ static CURLcode gopher_do(struct connectdata *conn, bool *done)
   /* Create selector. Degenerate cases: / and /1 => convert to "" */
   if(strlen(path) <= 2) {
     sel = (char *)"";
-    len = (int)strlen(sel);
+    len = strlen(sel);
   }
   else {
     char *newp;
diff --git a/lib/smb.c b/lib/smb.c
index 32f0ac889..e4b18fcf5 100644
--- a/lib/smb.c
+++ b/lib/smb.c
@@ -610,8 +610,8 @@ static CURLcode smb_send_and_recv(struct connectdata *conn, void **msg)
 
   /* Check if there is data in the transfer buffer */
   if(!smbc->send_size && smbc->upload_size) {
-    int nread = smbc->upload_size > UPLOAD_BUFSIZE ? UPLOAD_BUFSIZE :
-      (int) smbc->upload_size;
+    size_t nread = smbc->upload_size > UPLOAD_BUFSIZE ? UPLOAD_BUFSIZE :
+      smbc->upload_size;
     conn->data->req.upload_fromhere = conn->data->state.ulbuf;
     result = Curl_fillreadbuffer(conn, nread, &nread);
     if(result && result != CURLE_AGAIN)
diff --git a/lib/socks.c b/lib/socks.c
index 73326e5c2..81f3eda28 100644
--- a/lib/socks.c
+++ b/lib/socks.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -222,8 +222,8 @@ CURLcode Curl_SOCKS4(const char *proxy_user,
     ssize_t actualread;
     ssize_t written;
     ssize_t hostnamelen = 0;
-    int packetsize = 9 +
-      (int)strlen((char *)socksreq + 8); /* size including NUL */
+    ssize_t packetsize = 9 +
+      strlen((char *)socksreq + 8); /* size including NUL */
 
     /* If SOCKS4a, set special invalid IP address 0.0.0.x */
     if(protocol4a) {
diff --git a/lib/ssh-libssh.c b/lib/ssh-libssh.c
index 035f39fa7..002e1d96f 100644
--- a/lib/ssh-libssh.c
+++ b/lib/ssh-libssh.c
@@ -1290,7 +1290,7 @@ static CURLcode myssh_statemach_act(struct connectdata *conn, bool *block)
       if(sshc->readdir_attrs) {
         sshc->readdir_filename = sshc->readdir_attrs->name;
         sshc->readdir_longentry = sshc->readdir_attrs->longname;
-        sshc->readdir_len = (int)strlen(sshc->readdir_filename);
+        sshc->readdir_len = strlen(sshc->readdir_filename);
 
         if(data->set.ftp_list_only) {
           char *tmpLine;
@@ -1321,7 +1321,7 @@ static CURLcode myssh_statemach_act(struct connectdata *conn, bool *block)
           }
         }
         else {
-          sshc->readdir_currLen = (int)strlen(sshc->readdir_longentry);
+          sshc->readdir_currLen = strlen(sshc->readdir_longentry);
           sshc->readdir_totalLen = 80 + sshc->readdir_currLen;
           sshc->readdir_line = calloc(sshc->readdir_totalLen, 1);
           if(!sshc->readdir_line) {
@@ -1382,12 +1382,12 @@ static CURLcode myssh_statemach_act(struct connectdata *conn, bool *block)
         if(sshc->readdir_filename == NULL)
           sshc->readdir_len = 0;
         else
-          sshc->readdir_len = (int)strlen(sshc->readdir_tmp);
+          sshc->readdir_len = strlen(sshc->readdir_tmp);
         sshc->readdir_longentry = NULL;
         sshc->readdir_filename = sshc->readdir_tmp;
       }
       else {
-        sshc->readdir_len = (int)strlen(sshc->readdir_link_attrs->name);
+        sshc->readdir_len = strlen(sshc->readdir_link_attrs->name);
         sshc->readdir_filename = sshc->readdir_link_attrs->name;
         sshc->readdir_longentry = sshc->readdir_link_attrs->longname;
       }
diff --git a/lib/ssh.c b/lib/ssh.c
index 5d81f649c..0aaba9a6a 100644
--- a/lib/ssh.c
+++ b/lib/ssh.c
@@ -1933,17 +1933,17 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
       break;
 
     case SSH_SFTP_READDIR:
-      sshc->readdir_len = libssh2_sftp_readdir_ex(sshc->sftp_handle,
-                                                  sshc->readdir_filename,
-                                                  PATH_MAX,
-                                                  sshc->readdir_longentry,
-                                                  PATH_MAX,
-                                                  &sshc->readdir_attrs);
-      if(sshc->readdir_len == LIBSSH2_ERROR_EAGAIN) {
-        rc = LIBSSH2_ERROR_EAGAIN;
+      rc = libssh2_sftp_readdir_ex(sshc->sftp_handle,
+                                   sshc->readdir_filename,
+                                   PATH_MAX,
+                                   sshc->readdir_longentry,
+                                   PATH_MAX,
+                                   &sshc->readdir_attrs);
+      if(rc == LIBSSH2_ERROR_EAGAIN) {
         break;
       }
-      if(sshc->readdir_len > 0) {
+      if(rc > 0) {
+        sshc->readdir_len = (size_t) rc;
         sshc->readdir_filename[sshc->readdir_len] = '\0';
 
         if(data->set.ftp_list_only) {
@@ -1974,7 +1974,7 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
           }
         }
         else {
-          sshc->readdir_currLen = (int)strlen(sshc->readdir_longentry);
+          sshc->readdir_currLen = strlen(sshc->readdir_longentry);
           sshc->readdir_totalLen = 80 + sshc->readdir_currLen;
           sshc->readdir_line = calloc(sshc->readdir_totalLen, 1);
           if(!sshc->readdir_line) {
@@ -2008,13 +2008,13 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
           break;
         }
       }
-      else if(sshc->readdir_len == 0) {
+      else if(rc == 0) {
         Curl_safefree(sshc->readdir_filename);
         Curl_safefree(sshc->readdir_longentry);
         state(conn, SSH_SFTP_READDIR_DONE);
         break;
       }
-      else if(sshc->readdir_len <= 0) {
+      else if(rc < 0) {
         err = sftp_libssh2_last_error(sshc->sftp_session);
         result = sftp_libssh2_error_to_CURLE(err);
         sshc->actualcode = result?result:CURLE_SSH;
@@ -2029,16 +2029,16 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
       break;
 
     case SSH_SFTP_READDIR_LINK:
-      sshc->readdir_len =
+      rc =
         libssh2_sftp_symlink_ex(sshc->sftp_session,
                                 sshc->readdir_linkPath,
                                 curlx_uztoui(strlen(sshc->readdir_linkPath)),
                                 sshc->readdir_filename,
                                 PATH_MAX, LIBSSH2_SFTP_READLINK);
-      if(sshc->readdir_len == LIBSSH2_ERROR_EAGAIN) {
-        rc = LIBSSH2_ERROR_EAGAIN;
+      if(rc == LIBSSH2_ERROR_EAGAIN) {
         break;
       }
+      sshc->readdir_len = (size_t) rc;
       Curl_safefree(sshc->readdir_linkPath);
 
       /* get room for the filename and extra output */
diff --git a/lib/ssh.h b/lib/ssh.h
index 1c1355077..0620aac32 100644
--- a/lib/ssh.h
+++ b/lib/ssh.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -131,7 +131,7 @@ struct ssh_conn {
                                  quote command fails) */
   char *homedir;              /* when doing SFTP we figure out home dir in the
                                  connect phase */
-  int readdir_len, readdir_totalLen, readdir_currLen;
+  size_t readdir_len, readdir_totalLen, readdir_currLen;
   char *readdir_line;
   char *readdir_linkPath;
   /* end of READDIR stuff */
diff --git a/lib/tftp.c b/lib/tftp.c
index 61a3fef06..e5bc80b02 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -712,7 +712,7 @@ static CURLcode tftp_tx(tftp_state_data_t *state, tftp_event_t event)
   ssize_t sbytes;
   CURLcode result = CURLE_OK;
   struct SingleRequest *k = &data->req;
-  int cb; /* Bytes currently read */
+  size_t cb; /* Bytes currently read */
 
   switch(event) {
 
@@ -765,7 +765,7 @@ static CURLcode tftp_tx(tftp_state_data_t *state, tftp_event_t event)
     state->retries = 0;
     setpacketevent(&state->spacket, TFTP_EVENT_DATA);
     setpacketblock(&state->spacket, state->block);
-    if(state->block > 1 && state->sbytes < (int)state->blksize) {
+    if(state->block > 1 && state->sbytes < state->blksize) {
       state->state = TFTP_STATE_FIN;
       return CURLE_OK;
     }
@@ -781,7 +781,7 @@ static CURLcode tftp_tx(tftp_state_data_t *state, tftp_event_t event)
                                    &cb);
       if(result)
         return result;
-      state->sbytes += cb;
+      state->sbytes += (int)cb;
       state->conn->data->req.upload_fromhere += cb;
     } while(state->sbytes < state->blksize && cb != 0);
 
diff --git a/lib/transfer.c b/lib/transfer.c
index 298208703..7159d5c82 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -120,11 +120,12 @@ CURLcode Curl_get_upload_buffer(struct Curl_easy *data)
  * This function will call the read callback to fill our buffer with data
  * to upload.
  */
-CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
+CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
+                             size_t *nreadp)
 {
   struct Curl_easy *data = conn->data;
-  size_t buffersize = (size_t)bytes;
-  int nread;
+  size_t buffersize = bytes;
+  size_t nread;
 #ifdef CURL_DOES_CONVERSIONS
   bool sending_http_headers = FALSE;
 
@@ -144,11 +145,9 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
     data->req.upload_fromhere += (8 + 2); /* 32bit hex + CRLF */
   }
 
-  /* this function returns a size_t, so we typecast to int to prevent warnings
-     with picky compilers */
   Curl_set_in_callback(data, true);
-  nread = (int)data->state.fread_func(data->req.upload_fromhere, 1,
-                                      buffersize, data->state.in);
+  nread = data->state.fread_func(data->req.upload_fromhere, 1,
+                                 buffersize, data->state.in);
   Curl_set_in_callback(data, false);
 
   if(nread == CURL_READFUNC_ABORT) {
@@ -177,7 +176,7 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
 
     return CURLE_OK; /* nothing was read */
   }
-  else if((size_t)nread > buffersize) {
+  else if(nread > buffersize) {
     /* the read function returned a too large value */
     *nreadp = 0;
     failf(data, "read function returned funny value");
@@ -236,13 +235,13 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
 #ifdef CURL_DOES_CONVERSIONS
     {
       CURLcode result;
-      int length;
+      size_t length;
       if(data->set.prefer_ascii)
         /* translate the protocol and data */
         length = nread;
       else
         /* just translate the protocol portion */
-        length = (int)strlen(hexbuffer);
+        length = strlen(hexbuffer);
       result = Curl_convert_to_network(data, data->req.upload_fromhere,
                                        length);
       /* Curl_convert_to_network calls failf if unsuccessful */
@@ -257,7 +256,7 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
       infof(data, "Signaling end of chunked upload via terminating chunk.\n");
     }
 
-    nread += (int)strlen(endofline_native); /* for the added end of line */
+    nread += strlen(endofline_native); /* for the added end of line */
   }
 #ifdef CURL_DOES_CONVERSIONS
   else if((data->set.prefer_ascii) && (!sending_http_headers)) {
@@ -933,7 +932,7 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
       if(!k->upload_done) {
         /* HTTP pollution, this should be written nicer to become more
            protocol agnostic. */
-        int fillcount;
+        size_t fillcount;
         struct HTTP *http = k->protop;
 
         if((k->exp100 == EXP100_SENDING_REQUEST) &&
@@ -964,7 +963,7 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
         if(result)
           return result;
 
-        nread = (ssize_t)fillcount;
+        nread = fillcount;
       }
       else
         nread = 0; /* we're done uploading/reading */
diff --git a/lib/transfer.h b/lib/transfer.h
index df75f9a97..9263e5b69 100644
--- a/lib/transfer.h
+++ b/lib/transfer.h
@@ -51,7 +51,8 @@ int Curl_single_getsock(const struct connectdata *conn,
                         curl_socket_t *socks,
                         int numsocks);
 CURLcode Curl_readrewind(struct connectdata *conn);
-CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp);
+CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
+                             size_t *nreadp);
 CURLcode Curl_retry_request(struct connectdata *conn, char **url);
 bool Curl_meets_timecondition(struct Curl_easy *data, time_t timeofdoc);
 CURLcode Curl_get_upload_buffer(struct Curl_easy *data);