stdio and short file descriptors revisited

[John Baldwin]

Four years or so ago I cleaned up some of the stdio internals as fallout from 
running into problems with stdio using a short instead of an int to hold file 
descriptors.  Back then I got sidetracked with attempting to make FILE opaque 
and ended up never getting around to bumping _file from a short to an int.  I 
recently ran back into the SHRT_MAX limit at work again and came up with a 
patch to fix this.

To preserve the ABI, it is necessary to leave the existing short _file in 
place and add a new int _file to the end of the FILE structure.  Also, for old 
applications, the old _file (_ofile in the patch) must still be valid.  The 
approach I have taken is to bump the symbol version for routines that create 
FILE objects with a non-fake _file (fopen, fdopen, and freopen).  The old 
FBSD_1.0 variants still fail if an fd is greater than SHRT_MAX (and thus 
cannot be safely stored in _ofile).  The new FBSD_1.3 variants assign to both 
_file and _ofile if the fd is less than SHRT_MAX.  I also changed fileno()
to no longer be an inline macro in <stdio.h> but to always be a function call 
going forward.

If folks think this is ok, I'll hack up a modified version that hides _file
from outside consumers (rename it to _nfile or some such) and send it for a
ports-exp run before committing to make sure there aren't any 3rd party apps
accessing _file directly.

http://www.FreeBSD.org/~jhb/patches/stdio_file.patch

-- 
John Baldwin