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Compilation warning on AVR GCC

Posted by Bernardo on February 5, 2010

I'm using FreeRTOS on a board I made with an AT90USB647 and the compiler issues a warning on line 422 of tasks.c:

FreeRTOS/tasks.c: In function 'xTaskGenericCreate':
FreeRTOS/tasks.c:422: error: cast from pointer to integer of different size
FreeRTOS/tasks.c:422: error: cast to pointer from integer of different size

in line 422 of tasks.c i can see:
pxTopOfStack = ( portSTACK_TYPE * ) ( ( ( unsigned long ) pxTopOfStack ) & ( ( unsigned long ) ~portBYTE_ALIGNMENT_MASK ) );

in portmacro.h (based on portmacro.h in the ATMega323 example) i have:
#define portSTACK_TYPEunsigned portCHAR

is this the correct portSTACK_TYPE for the AVR uController?
What should i do? change portSTACK_TYPE or change line 422 of tasks.c?
If i replace 'long' by 'int' in line 422 the warning disapears and FreeRTOS works but is this correct?

Bernardo Marques.

RE: Compilation warning on AVR GCC

Posted by Richard on February 5, 2010
This warning has arrisen from a recent change and occurs on ports where the stack type is smaller than the pointer type. I think changing the unsigned long casts to portBASE_TYPE cases might be ok, but would have to check each port individually.


RE: Compilation warning on AVR GCC

Posted by Bernardo on February 9, 2010
Nope. It cannot be a cast to portBASE_TYPE, it will make it worse. I suppose that in AVR GCC a pointer has two bytes and the base type on the AVR is 8-bit. As pxTopOfStack must be casted to a 16-bit integer it must be to either int or portSHORT.

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