Date: Mon, 1 Oct 2012 12:21:13 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: arch@freebsd.org Subject: Re: stdio and short file descriptors revisited Message-ID: <20121001092113.GH35915@deviant.kiev.zoral.com.ua> In-Reply-To: <201209281847.39663.jhb@freebsd.org> References: <201209281847.39663.jhb@freebsd.org>
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[-- Attachment #1 --] On Fri, Sep 28, 2012 at 06:47:39PM -0400, John Baldwin wrote: > 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 The corner case left unhandled is the situation where we have a dso which is linked against FBSD_1.0 version of libc, but which gets FILE * as an API argument for some of its exported routines. If the implementation uses fileno(3), it would fail. I have no idea how to fix this, most likely, the issue is not fixable at all. Workaround seems to be to force the __isthreaded to 1. Might be, as an ugly hack, some flag could be added to the stdbuf(1), if anybody cares enough. Otherwise, the patch looks good. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAlBpYIkACgkQC3+MBN1Mb4gCHwCg1XHzpsvs6LeerJaEtZXC87/x 0dEAoPOL19RkL5gOVOc0lvvzKTsMFjY+ =6tu+ -----END PGP SIGNATURE-----
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