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C99 specifies that the EOF condition on a file is "sticky": once EOF has been encountered, all subsequent reads should continue to return EOF until the file is closed or something clears the "end-of-file indicator" (e.g. fseek, clearerr). This is arguably a change from C89, where the wording was ambiguous; the BSDs always had sticky EOF, but the System V lineage would attempt to read from the underlying fd again. GNU libc has followed System V for as long as we've been using libio, but nowadays C99 conformance and BSD compatibility are more important than System V compatibility. You might wonder if changing the _underflow impls is sufficient to apply the C99 semantics to all of the many stdio functions that perform input. It should be enough to cover all paths to _IO_SYSREAD, and the only other functions that call _IO_SYSREAD are the _seekoff impls, which is OK because seeking clears EOF, and the _xsgetn impls, which, as far as I can tell, are unused within glibc. The test programs in this patch use a pseudoterminal to set up the necessary conditions. To facilitate this I added a new test-support function that sets up a pair of pty file descriptors for you; it's almost the same as BSD openpty, the only differences are that it allocates the optionally-returned tty pathname with malloc, and that it crashes if anything goes wrong. [BZ #1190] [BZ #19476] * libio/fileops.c (_IO_new_file_underflow): Return EOF immediately if the _IO_EOF_SEEN bit is already set; update commentary. * libio/oldfileops.c (_IO_old_file_underflow): Likewise. * libio/wfileops.c (_IO_wfile_underflow): Likewise. * support/support_openpty.c, support/tty.h: New files. * support/Makefile (libsupport-routines): Add support_openpty. * libio/tst-fgetc-after-eof.c, wcsmbs/test-fgetwc-after-eof.c: New test cases. * libio/Makefile (tests): Add tst-fgetc-after-eof. * wcsmbs/Makefile (tests): Add tst-fgetwc-after-eof.
46 lines
1.8 KiB
C
46 lines
1.8 KiB
C
/* Support functions related to (pseudo)terminals.
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Copyright (C) 2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _SUPPORT_TTY_H
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#define _SUPPORT_TTY_H 1
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struct termios;
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struct winsize;
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/** Open a pseudoterminal pair. The outer fd is written to the address
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A_OUTER and the inner fd to A_INNER.
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If A_NAME is not NULL, it will be set to point to a string naming
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the /dev/pts/NNN device corresponding to the inner fd; space for
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this string is allocated with malloc and should be freed by the
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caller when no longer needed. (This is different from the libutil
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function 'openpty'.)
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If TERMP is not NULL, the terminal parameters will be initialized
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according to the termios structure it points to.
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If WINP is not NULL, the terminal window size will be set
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accordingly.
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Terminates the process on failure (like xmalloc). */
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extern void support_openpty (int *a_outer, int *a_inner, char **a_name,
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const struct termios *termp,
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const struct winsize *winp);
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#endif
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