feat(newlib): Add newlib platform function

components/freertos/include/port/freertos/portmacro.h

@@ -77,6 +77,17 @@ extern "C" {
 #include    <xtensa/xtruntime.h>
 #include    "xtensa_rtos.h"
 
+#if defined(configUSE_NEWLIB_REENTRANT) && configUSE_NEWLIB_REENTRANT == 1
+#if defined(CONFIG_NEWLIB_LIBRARY_LEVEL_NORMAL) || defined(CONFIG_NEWLIB_LIBRARY_LEVEL_NANO)
+#include "esp_newlib.h"
+
+#define _impure_ptr _global_impure_ptr
+
+#undef _REENT_INIT_PTR
+#define _REENT_INIT_PTR(p) esp_reent_init(p)
+#endif
+#endif
+
 /*-----------------------------------------------------------
  * Port specific definitions.
  *

components/freertos/port/impure.c

@@ -0,0 +1,44 @@
+// Copyright 2018-2019 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.
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+static struct _reent impure_data;
+struct _reent *_global_impure_ptr = &impure_data;
+
+struct _reent *__getreent()
+{
+    extern char _xt_isr_status;
+
+    /*
+     * Locking mutex(only mutex, not ISR mutex) at the following three
+     * state may cause OS death. So we use a extra _reent data instead
+     * of task private reent data.
+     * 
+     * But although at the state none of "taskSCHEDULER_RUNNING",  exception
+     * can cause CPU swicth context, then Locking mutex may cause OS death.
+     * So we command that use ets_printf(ROM function) instead of "printf"
+     * at exception and system kernal critical state.
+     */
+    if (_xt_isr_status 
+        || !xTaskGetCurrentTaskHandle()
+        || xTaskGetSchedulerState() != taskSCHEDULER_RUNNING)
+        return &impure_data;
+
+    /*
+     * When scheduler starts, _global_impure_ptr = pxCurrentTCB->xNewLib_reent.
+     */
+    return _global_impure_ptr;
+}