Alan Carvalho de Assis wrote:
> Hi Borut,
>
> 2007/11/6, Borut Razem <[EMAIL PROTECTED]>:
>
>> #define SAVE_TASK_CTX(stack_low, stack_high) \
>> do { \
>> /* Disable global interrupt. */ \
>> _asm \
>> bcf INTCON, 6, 0 \
>> _endasm; \
>> _asm \
>> movff STATUS, PREINC1 \
>> _endasm; \
>> _asm \
>> movff WREG, PREINC1 \
>> _endasm; \
>> /* Store the necessary registers to the stack. */ \
>> ...
>> } while (0)
>>
>>
>> so that the following cases work correctly:
>>
>> if (...)
>> SAVE_TASK_CTX(stack_low, stack_high);
>>
>>
>> if (...)
>> SAVE_TASK_CTX(stack_low, stack_high);
>> else
>> ...
>>
>>
>
> Yes. I saw this tips at kernelnewbies.org some years ago. I'm
> wondering because the original code works, see the pro_man.c from
> PICos18:
>
> if (kernelState & USER)
> SAVE_TASK_CTX(stack_low, stack_high);
> SCHEDULE;
>
> Very strange!
>
> Cheers,
>
>
Your original code wouldn't work in the second example:
if (...)
SAVE_TASK_CTX(stack_low, stack_high);
else
...
because there is a semicolon (an additional null statement) before else.
Borut
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