Re: Of course, I have a memory corruption, but I'm not able to fix it...

[BERTRAND Joël]

Trampas Stern a écrit :
> You also  need to send the rest of the code. 
> 
> For example it could be that rx_len is where memory overflow is happening
> 
> cascade:
> *    rx_len = sizeof(sak);*
> snprintf(t, 3, "%d", (*tag).level);
> 
> On Thu, May 20, 2021 at 11:07 AM Trampas Stern <tstern@nc.rr.com
> <mailto:tstern@nc.rr.com>> wrote:
> 
>     Try  changing this:
>     unsigned char           t[3];
> 
>     to this
>     unsigned char           t[4];
> 
>     Then see if your problem goes away. 

        I have tried to replace t[3] by t[8] before my first post, same result.
I have tried also to add a delay after each stty_print() and I obtain
the same corruption.

>     So snprintf() is not well documented...  is the size parameter
>     including null terminator or not?  

        snprintf always contains null terminator.

>     Even worse is when you get to
>     multiple threads (ISR handlers) is snprintf() reentrant? 
> 
>     Generally I write my own snprintf() so that I know what it does and
>     make sure it is reentrant. This is not as optimized but I know what
>     the results are.  
> 
>     You also have lots of other things to consider for example the AVR
>     is Harvard machine so code like this:
>     stty_print("Anticol ACF\r\n");
>     actually will copy string from flash to RAM and thus use more RAM.  

        I have found a very strange bug.

uint8_t
iso14443a_anticol(uint8_t wup, rfid_tag_t *tag)
{
...

    (*tag).state = ISO14443A_STATE_ANTICOL_RUNNING;
    (*tag).level = ISO14443A_LEVEL_CL1;

snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
snprintf(t, 3, "%02X", (*tag).level);
        vfd_print(t); vfd_print(" (0)\r\n");
//vfd_print("1"); vfd_print(" (0)\r\n");
snprintf(t, 3, "%02X", (*tag).level); stty_print(t); stty_print(" (0)\r\n");
snprintf(t, 3, "%02X", (*tag).level); stty_print(t); stty_print("
(0.0)\r\n");
cascade:
    rx_len = sizeof(sak);
snprintf(t, 3, "%02X", (*tag).level); stty_print(t); stty_print("
(0.1)\r\n");
...

        This code runs as expected (please note vfd_print(t); vfd_print("
(0)\r\n");).

        On VFD screen, I obtain "01 (0)".

        If I replace this line by vfd_print("01 (0)\r\n"); I can see my memory
corruption again.

        If I deplace this line after snprintf(t, 3, "%02X", (*tag).level);
stty_print(t); stty_print(" (0.0)\r\n"); program runs as expected.

        If I remove this line, memory corruption again.

        My avr-gcc is an old release (5.4 given by debian). I will try a recent
gcc.

        JB