[avr-gcc-list] How to pass a struct in Interrupt

[Eric Fu]

Hi,

I'm trying to write a simple Interrupt driven UART.
 
I defined a struct  in UART.c like:
typedef struct UART
{
 byte RxBuf[RX_BUFFER_SIZE];
 volatile byte RxHead;
 volatile byte RxTail;
    .
    .

 }UART;

UART uart0;

And in isr.c, I declare and define:
extern UART uart0;
SIGNAL(SIG_UART_RECV) //USART RX complete INT
{
 byte data;
 byte tmphead;

 /* Read the received data */
 data = UDR;                 
 /* Calculate buffer index */
 tmphead = ( uart0.RxHead + 1 ) & RX_BUFFER_MASK;
 uart0.RxHead = tmphead;      /* Store new index */
    .
    .
}

I have the following compile error:
Compiling: isr.c
avr-gcc -c -mmcu=atmega16 -I. -g -Os -funsigned-char -funsigned-bitfields 
-fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-adhlns=isr.lst 
-Ic:/pjt2/avr/PJT_inc -std=gnu99 isr.c -o isr.o
isr.c:17: error: parse error before "uart0"
isr.c:17: warning: type defaults to `int' in declaration of `uart0'
isr.c:17: warning: data definition has no type or storage class
isr.c: In function `__vector_11':
isr.c:84: error: request for member `RxHead' in something not a structure or 
union
isr.c:85: error: request for member `RxHead' in something not a structure or 
union
isr.c:87: error: request for member `RxTail' in something not a structure or 
union
isr.c:92: error: request for member `RxBuf' in something not a structure or 
union
isr.c: In function `__vector_12':
isr.c:104: error: request for member `TxHead' in something not a structure or 
union
isr.c:104: error: request for member `TxTail' in something not a structure or 
union
isr.c:107: error: request for member `TxTail' in something not a structure or 
union
isr.c:108: error: request for member `TxTail' in something not a structure or 
union
isr.c:110: error: request for member `TxBuf' in something not a structure or 
union
make: *** [isr.o] Error 1

It seems the compiler doesn't recognise an external struct definition. Could 
anyone give me a hint to get around this?
Thanks.

Eric Fu