text: // Copyright 2015-2016 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 <string.h>
  #include <stdbool.h>
  #include <sys/types.h>
  #include <unistd.h>
  #include <errno.h>
  #include <sys/reent.h>
  #include <stdlib.h>
  #include "esp_attr.h"
  #include "freertos/FreeRTOS.h"
  #include "esp_heap_caps.h"
  
  
  /*
   These contain the business logic for the malloc() and realloc() implementation. Because of heap tracing
   wrapping reasons, we do not want these to be a public api, however, so they're not defined publicly.
  */
  extern void *heap_caps_malloc_default( size_t size );
  extern void *heap_caps_realloc_default( void *ptr, size_t size );
  
  
  void* IRAM_ATTR _malloc_r(struct _reent *r, size_t size)
  {
      return heap_caps_malloc_default( size );
  }
  
  void IRAM_ATTR _free_r(struct _reent *r, void* ptr)
  {
      heap_caps_free( ptr );
  }
  
  void* IRAM_ATTR _realloc_r(struct _reent *r, void* ptr, size_t size)
  {
      return heap_caps_realloc_default( ptr, size );
  }
  
  void* IRAM_ATTR _calloc_r(struct _reent *r, size_t nmemb, size_t size)
  {
      void *result;
      size_t size_bytes;
      if (__builtin_mul_overflow(nmemb, size, &size_bytes)) {
          return NULL;
      }
  
      result = malloc(size_bytes);
      if (result != NULL) {
          bzero(result, size_bytes);
      }
      return result;
  }
  
  int _system_r(struct _reent *r, const char *str)
  {
      __errno_r(r) = ENOSYS;
      return -1;
  }
  
  int _raise_r(struct _reent *r, int sig)
  {
      abort();
  }
  
  void* _sbrk_r(struct _reent *r, ptrdiff_t sz)
  {
      abort();
  }
  
  int _getpid_r(struct _reent *r)
  {
      __errno_r(r) = ENOSYS;
      return -1;
  }
  
  int _kill_r(struct _reent *r, int pid, int sig)
  {
      __errno_r(r) = ENOSYS;
      return -1;
  }
  
  void _exit(int __status)
  {
      abort();
  }
  
  