15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20 <<fflush>>, <<fflush_unlocked>>---flush buffered file output
56 Additionally, if <[fp]> is a seekable input stream visiting a file
58 unread byte, useful for obeying POSIX semantics when ending a process
61 <<fflush_unlocked>> is a non-thread-safe version of <<fflush>>.
62 <<fflush_unlocked>> may only safely be used within a scope
64 function may safely be used in a multi-threaded program if and only
66 object, as is the case after a successful call to the flockfile() or
71 reentrant versions, where the extra argument <[reent]> is a pointer to
72 a reentrancy structure, and <[fp]> must not be NULL.
75 <<fflush>> returns <<0>> unless it encounters a write error; in that
82 <<fflush_unlocked>> is a BSD extension also provided by GNU libc.
98 /* Flush a single file, or (if fp is NULL) all files.  */
111   flags = fp->_flags;  in _sflush()
115       /* For a read stream, an fflush causes the next seek to be  in _sflush()
116          unoptimized (i.e. forces a system-level seek).  This conforms  in _sflush()
118       fp->_flags |= __SNPT;  in _sflush()
121       /* For a seekable stream with buffered read characters, we will attempt  in _sflush()
122          a seek to the current position now.  A subsequent read will then get  in _sflush()
127          to miss a code scenario.  */  in _sflush()
128       if ((fp->_r > 0 || fp->_ur > 0) && fp->_seek != NULL)  in _sflush()
137 	  /* Save last errno and set errno to 0, so we can check if a device  in _sflush()
138 	     returns with a valid position -1.  We restore the last errno if  in _sflush()
143 	  if (fp->_flags & __SOFF)  in _sflush()
144 	    curoff = fp->_offset;  in _sflush()
150 	      if (fp->_flags & __SL64)  in _sflush()
151 		curoff = fp->_seek64 (fp->_cookie, 0, SEEK_CUR);  in _sflush()
154 		curoff = fp->_seek (fp->_cookie, 0, SEEK_CUR);  in _sflush()
155 	      if (curoff == -1L && _REENT_ERRNO(ptr) != 0)  in _sflush()
164 		    fp->_flags |= __SERR;  in _sflush()
168           if (fp->_flags & __SRD)  in _sflush()
172               curoff -= fp->_r;  in _sflush()
174                 curoff -= fp->_ur;  in _sflush()
178 	  if (fp->_flags & __SL64)  in _sflush()
179 	    curoff = fp->_seek64 (fp->_cookie, curoff, SEEK_SET);  in _sflush()
182 	    curoff = fp->_seek (fp->_cookie, curoff, SEEK_SET);  in _sflush()
183 	  if (curoff != -1 || _REENT_ERRNO(ptr) == 0  in _sflush()
189 	      fp->_flags &= ~__SNPT;  in _sflush()
191 	      fp->_r = 0;  in _sflush()
192 	      fp->_p = fp->_bf._base;  in _sflush()
193 	      if ((fp->_flags & __SOFF) && (curoff != -1 || _REENT_ERRNO(ptr) == 0))  in _sflush()
194 		fp->_offset = curoff;  in _sflush()
201 	      fp->_flags |= __SERR;  in _sflush()
207   if ((p = fp->_bf._base) == NULL)  in _sflush()
212   n = fp->_p - p;		/* write this much */  in _sflush()
219   fp->_p = p;  in _sflush()
220   fp->_w = flags & (__SLBF | __SNBF) ? 0 : fp->_bf._size;  in _sflush()
224       t = fp->_write (fp->_cookie, (char *) p, n);  in _sflush()
227           fp->_flags |= __SERR;  in _sflush()
231       n -= t;  in _sflush()
244   return (fp->_flags & __SWR) ?  _sflush ( fp) : 0;  in _sflushw()
260      called for the first time on a std stream.  This std  in fflush()
261      stream can belong to a reentrant struct that is not  in fflush()
266      are two alternatives to fix this:  1) make a reentrant fflush  in fflush()
268      and return immediately before performing a CHECK_INIT.  Choice  in fflush()
270   if (fp->_bf._base == NULL)  in fflush()
276   if (!fp->_flags)  in fflush()