Merge branch 'bugfix/read_eof_no_vfs_4.4' into 'release/v4.4'

newlib: fix return value of no-VFS _read_r if nothing received (v4.4)

See merge request espressif/esp-idf!18160

components/newlib/syscalls.c

@@ -1,16 +1,8 @@
-// Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+/*
+ * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 #include <stdbool.h>
 #include <stdlib.h>
@@ -59,6 +51,10 @@ ssize_t _read_r_console(struct _reent *r, int fd, void * data, size_t size)
                 break;
             }
         }
+        if (received == 0) {
+            errno = EWOULDBLOCK;
+            return -1;
+        }
         return received;
     }
     __errno_r(r) = EBADF;