[PATCH] _fwalk walks through thread local FILE pointer

[Jeff Johnston]

The reentrancy model hasn't changed dramatically.  It is just files are 
managed in the global reentrancy structure now.  See the change on 08-22.

-- Jeff J.

Joel Sherrill wrote:

> My understanding of the reentrancy code in newlib must have gotten
> totally out of sync with reality.  Is there any documentation
> I can read to catch up and get educated again?
>
> --joel
>
> Jeff Johnston wrote:
>
>> I think that the stdin/stdout/stderr for the thread should also be 
>> walked in addition to the global list for now.  I don't think that 
>> should cause problems with Cygwin but if so, we can add an #ifdef check.
>
> >
>
>> -- Jeff J.
>>
>> Thomas Pfaff wrote:
>>
>>> Take a look at findfp.c and you will see that all FILE pointers are 
>>> hold in _GLOBAL_REENT, therefore _fwalk simply does not walk through 
>>> the real FILE pointer list, but through the thread lokal ones which 
>>> will contain only stdin, stdout and stderr.
>>>
>>> The obsolete REENT ptr can be removed but thats Jeffs decision.
>>>
>>> You can search the list why _GLOBAL_REENT was introduced some time 
>>> ago. The former implementation where every thread has its own 
>>> pointer list was incorrect, FILE pointers are process global objects.
>>>
>>> There is still a problem with stdin, stdout and stderr because every 
>>> thread has its own buffers for these files. Cygwin has a workaround 
>>> for this problem, it maps the thread lokal stdin, stdout and stderr 
>>> to _GLOBAL_REENT aka _impure_ptr FILE pointers. I think that this 
>>> will a working solution for other platforms as well.
>>>
>>> Thomas
>>>
>>> Joel Sherrill wrote:
>>>
>>>> This isn't right.  You are passed a REENT pointer and cannot
>>>> simply ignore it.
>>>>
>>>> This will break any code that depends upon the existing
>>>> behavior.  In RTEMS, we use _fwalk as it exists to
>>>> implement sync() and walk each thread's open files.
>>>> It is also used as part of the per-thread cleanup
>>>> dynamically.
>>>>
>>>> If you want to have NULL ptr argument imply the global
>>>> reent, great but don't break it.
>>>>
>>
>
>