Problem with malloc

[Filya]

Hi,

I need to create a dynamic array to send a different number of bytes of data using TWI.
Here is how I create an array:

void twi_Eeprom_Write(uint8_t *pBuffer, uint32_t WriteAddr, uint32_t NumBytesWritten)
{
  ret_code_t err_code;
  uint8_t SendAddr = 0;
  uint8_t *reg;
  reg = (uint8_t *)malloc((NumBytesWritten+2) * sizeof(uint8_t));
   
  SendAddr = ((EEPROM_ADDR & 0xFC) | ((uint8_t)(WriteAddr >> 15) & 0x02));//A0 - write
  reg[0] = (uint8_t)(((WriteAddr) & 0xFF00) >> 8);
  reg[1] = (uint8_t)((WriteAddr) & 0x00FF);
  for (uint8_t i = 0; i < NumBytesWritten; i++)
  {
    reg[i+2] = pBuffer[i];
  }
  
  err_code = nrf_drv_twi_tx(&m_twi_eeprom, SendAddr, reg, sizeof(reg), false);
  APP_ERROR_CHECK(err_code);
  
  free(reg);
  
  TWI_Delay(10);
}

When using the malloc function, I always get an array with a size of 4, regardless of the value of the X variable. I also tried to use the nrf_malloc function. The result is exactly the same.

Maybe there are ideas why he doesn't want to create an array of the required size.

Thank you in advance

[awneil]

Filya said:

I need to create a dynamic array to send a different number of bytes of data using TW

No, you don't need a dynamic array for that!

You could just create a "normal" array of your maximum size.

Filya said:

I always get an array with a size of 4

How do you determine that ?

Filya said:

regardless of the value of the X variable

What "X variable" ?

You are also making the classic mistake of not checking the return value from malloc before using it!