RTEMS5 _REENT

[Sebastian Huber]

On 07/11/2018 08:23, Ian Caddy wrote:
>
>>>
>>> Or should this be fixed to check whether multi-tasking is running 
>>> before checking the currently running thread, we do this in some of 
>>> our other code?
>>
>> Code which runs before the idle threads are created should not use 
>> complex Newlib functions. Unfortunately snprintf() is a complex 
>> Newlib function. I think we need a low level replacement for 
>> snprintf() which could be used during BSP initialization for example. 
>> This could be a simple wrapper for _IO_Printf().
>>
>> I had a similar issue here:
>>
>> https://lists.rtems.org/pipermail/devel/2018-September/023013.html
>>
>
> Thanks, I must have skipped over that one from a short time ago.
>
> The problem is that we end up doing quite a lot of complicated things 
> before multi-tasking is started, and there is not going to be a simple 
> way around that for us with quite a large code base.
>
> I am still wondering whether or not I can change the __getreent 
> function to detect whether multi-tasking has started yet or not and 
> either return the task executing element or return the _GLOBAL_REENT 
> for the time before.
>
> I am wondering what other side effects there will be and whether this 
> is better than defining CONFIGURE_DISABLE_NEWLIB_REENTRANCY. I might 
> try an experiment to check which method might be better for us. 

If you update to the current master

https://git.rtems.org/rtems/commit/?id=d1f7204649ff7c8bed36eab5af20c1a108af8b14

then you could try to add this to the module which contains your 
application configuration:

#define CONFIGURE_DISABLE_NEWLIB_REENTRANCY

struct _reent *__getreent(void)
{
   Thread_Control *executing;

   executing = _Thread_Get_executing();

   if (executing != NULL) {
     return executing->libc_reent;
   } else {
     return _GLOBAL_REENT;
   }
}

-- 
Sebastian Huber, embedded brains GmbH

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