[RFA] enable dynamic (thread safe) reents

[Thomas Pfaff]

Christopher Faylor wrote:
> On Fri, May 16, 2003 at 02:12:16PM +0200, Thomas Pfaff wrote:
> 
>>Thomas Pfaff wrote:
>>
>>
>>>While single threaded apps should keep run without problems (_impure_ptr
>>>is still used for the mainthread) multithreaded apps should be recompiled
>>>to get the full power of the thread safe reents. This is due the
>>>fact that _RRENT is used in some newlib headers directly. Unfortunately
>>>this affects also static libs, therefore this is will be a longer
>>>transition.
>>>
>>
>>TTTT,
>>
>>this will only affect stdio
>>
>>stdio.h:147:#define     stdin   (_REENT->_stdin)
>>stdio.h:148:#define     stdout  (_REENT->_stdout)
>>stdio.h:149:#define     stderr  (_REENT->_stderr)
>>
>>and i consider this harmless.
> 
> 
> Does this imply that using a DLL rebuilt like this will require recompilation
> of static libraries using errno?
> 

No. errno is handled differently.

#ifndef _REENT_ONLY
#define errno (*__errno())
extern int *__errno _PARAMS ((void));
#endif

and __errno is in newlib implemented as

int *
__errno ()
{
   return &_REENT->_errno;
}

Therefore threads safe errnos are automatically enabled when newlib is 
compiled with __DYNAMIC_REENT__.

Unfortunately stdin, stdout and stderr were defined with _REENT 
directly. Sigh.

Thomas