sysmem.c

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/* Includes */
#include <errno.h>
#include <stdint.h>
 
static uint8_t *__sbrk_heap_end = NULL;
 
void *_sbrk(ptrdiff_t incr)
{
  extern uint8_t _end; /* Symbol defined in the linker script */
  extern uint8_t _estack; /* Symbol defined in the linker script */
  extern uint32_t _Min_Stack_Size; /* Symbol defined in the linker script */
  const uint32_t stack_limit = (uint32_t)&_estack - (uint32_t)&_Min_Stack_Size;
  const uint8_t *max_heap = (uint8_t *)stack_limit;
  uint8_t *prev_heap_end;
 
  /* Initialize heap end at first call */
  if (NULL == __sbrk_heap_end)
  {
    __sbrk_heap_end = &_end;
  }
 
  /* Protect heap from growing into the reserved MSP stack */
  if (__sbrk_heap_end + incr > max_heap)
  {
    errno = ENOMEM;
    return (void *)-1;
  }
 
  prev_heap_end = __sbrk_heap_end;
  __sbrk_heap_end += incr;
 
  return (void *)prev_heap_end;
}