Re: [avr-gcc-list] issues with struct and volatile

[klaas]

Try this:

struct
{
  uint8_t *tx_head;
  uint8_t volatile *tx_tail;
  uint8_t tx_buffer[DBG_BUF_SZ];

  /* blah blah */
  uint8_t dbg_timer;
} dbg_serial_port;


Declare the pointer volatile, not the value it is pointing to

Pink Boy wrote:
> Hi,
>
> I recently run into an issue with a struct with some volatile members and 
> was wondering is this is a problem with me or gcc, ar avr-gcc.
>
> I have a structure used to define a buffer for a serial port somewhat like
> this.
>
> struct
> {
>    uint8_t *tx_head;
>    volatile uint8_t *tx_tail;
>    uint8_t tx_buffer[DBG_BUF_SZ];
>
>    /* blah blah */
>    uint8_t dbg_timer;
> } dbg_serial_port;
>
> In my main loop I have a code that waits to see if the buffer is full.
>
>      while(dbg_serial_port.tx_head == dbg_serial_port.txtail)
>           ;
>
> And of course with compiler flags set to optimize for size -Os it hangs
> and waits forever.
>
> The only way to get it to work is to declare the whole structure and 
> tx_tail as volatile.  I'd be just annoyed, but if I do that I get a whole
> bunch of compiler warnings on stuff like
>
> uint8_t *temp = dbg_serial_port.tx_head;
>
> I can fix those with a cast but doing that is like going after a fly 
> with a hammer.
>
> Is this a bug with gcc's handling of volatile or just me?
>
> PS: Using the WinAvr 20090313.
>
> Matt
>
>
> _______________________________________________
> AVR-GCC-list mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
>
>
>