[pa3efu@yahoo.com: Re: setvbuf/setlinebuf issue] Thomas can you comment?

Thomas Pfaff tpfaff@gmx.net
Fri Sep 19 07:26:00 GMT 2003

Corinna Vinschen wrote:
> On Fri, Sep 19, 2003 at 08:11:10AM +0200, Thomas Pfaff wrote:
>>This is another problem with __DYNAMIC_REENT__, where every thread has 
>>its own stdin, stdout and stderr FIL pointer.
>>I already submitted a patch to newlib which should hopefully fix this. 
>>After its acceptance it requires 3 additional functions to be exported 
>>in cygwin.din.
>>The bad news are that this patch again needs a recompilation of all user 
>>apps, starting with gcc to get it into libstdc++, because the stdin, 
>>stdout and stderr defines have changed again.
> Is it backward compatible, though?  Will old apps still work?

All apps will still work.

In short terms the patch will revert stdin, -out and -err back to 
_impure_ptr instead of the thread local reent. These defines were also 
used by older apps previour to the __DYNAMIC_REENT__change.

This affects only multithreaded apps and of course the libs they are 
using that were compiled in the meantime, and they will continue to 
work, but the bug will remain until recompilation.

The reason for this is the stdio header:

#ifndef _REENT_ONLY
#define	stdin	(_REENT->_stdin)
#define	stdout	(_REENT->_stdout)
#define	stderr	(_REENT->_stderr)
#else /* _REENT_ONLY */
#define	stdin	(_impure_ptr->_stdin)
#define	stdout	(_impure_ptr->_stdout)
#define	stderr	(_impure_ptr->_stderr)
#endif /* _REENT_ONLY */

To avoid this in the future (if it will be accepted in newlib) i have 
changed the defines to

extern  __FILE **__stdin _PARAMS ((void));
extern  __FILE **__stdout _PARAMS ((void));
extern  __FILE **__stderr _PARAMS ((void));
#define stdin (*__stdin())
#define stdout (*__stdout())
#define stderr (*__stderr())

which will allow to make changes without recompiling everything.


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