[PATCH] _fwalk walks through thread local FILE pointer

[Thomas Pfaff]

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.
>