B4R Question Different behaviour of ByteConverter.ArrayCopy in different boards

[hatzisn]

This is not a question but rather a conclusion. I do not know where to post this message since I do not think it is a bug of B4R but rather a difference in behaviour derived from the ESP8266 core. Consider the following code:

#Region Project Attributes
    #AutoFlushLogs: True
    #CheckArrayBounds: True
    #StackBufferSize: 300
#End Region
'Ctrl+Click to open the C code folder: ide://run?File=%WINDIR%\System32\explorer.exe&Args=%PROJECT%\Objects\Src

Sub Process_Globals
    Public Serial1 As Serial
    Dim bc As ByteConverter
End Sub

Private Sub AppStart
    Serial1.Initialize(9600)
    Log("AppStart")
    Dim arr1(200) As Byte
    Dim arr2(210) As Byte
   
    For ii= 0 To 199
        arr1(ii) = 10
    Next
   
    For ii= 0 To 209
        arr2(ii) = 50
    Next
   
    bc.ArrayCopy(arr2, arr1)
   
    For ii = 0 To arr1.Length - 1
        Log(ii, "-", arr1(ii))
    Next
   
    Log("Ok")
End Sub

If you run it in an Arduino Nano (mine uses the old bootloader) it will work fine. If you run it though in an ESP8266 the code will break. If you try to get arr1 larger f.e. Dim arr1(211) As Byte it will work fine. Thus in Arduino Nano it copies larger arrays to smaller ones but in ESP8266 it does not and the code breaks. What one has to do is to make always sure that the length of the array is at least as the one it will copy to it for the ESP8266.

 

[janderkan]

Or use arraycopy2 where you can specify how many bytes to copy.

 

[hatzisn]

Or use arraycopy2 where you can specify how many bytes to copy.

Yes I know this. I just wanted to point out the different behaviour between Arduino & ESP8266.

 

[Erel]

The conclusion is wrong. It will also fail in Arduino in many other cases.

The compiler allocated 200 bytes to arr1 and you copied 210 bytes. In this specific example nothing important was stored on the stack, after the space for arr1. In other cases it will corrupt the stack.

 

[hatzisn]

I ended up in this conclusion because of what is written in the explanation of ByteConverter.ArrayCopy as seen in the following picture: