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2cc7bad0ae
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.
110 lines
2.8 KiB
C
110 lines
2.8 KiB
C
/* Open a pseudoterminal.
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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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#include <support/tty.h>
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#include <support/check.h>
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#include <support/support.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <fcntl.h>
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#include <termios.h>
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#include <sys/ioctl.h>
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#include <unistd.h>
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/* As ptsname, but allocates space for an appropriately-sized string
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using malloc. */
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static char *
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xptsname (int fd)
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{
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int rv;
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size_t buf_len = 128;
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char *buf = xmalloc (buf_len);
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for (;;)
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{
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rv = ptsname_r (fd, buf, buf_len);
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if (rv)
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FAIL_EXIT1 ("ptsname_r: %s", strerror (errno));
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if (memchr (buf, '\0', buf_len))
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return buf; /* ptsname succeeded and the buffer was not truncated */
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buf_len *= 2;
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buf = xrealloc (buf, buf_len);
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}
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}
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void
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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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{
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int outer = -1, inner = -1;
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char *namebuf = 0;
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outer = posix_openpt (O_RDWR | O_NOCTTY);
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if (outer == -1)
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FAIL_EXIT1 ("posix_openpt: %s", strerror (errno));
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if (grantpt (outer))
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FAIL_EXIT1 ("grantpt: %s", strerror (errno));
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if (unlockpt (outer))
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FAIL_EXIT1 ("unlockpt: %s", strerror (errno));
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#ifdef TIOCGPTPEER
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inner = ioctl (outer, TIOCGPTPEER, O_RDWR | O_NOCTTY);
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#endif
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if (inner == -1)
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{
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/* The kernel might not support TIOCGPTPEER, fall back to open
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by name. */
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namebuf = xptsname (outer);
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inner = open (namebuf, O_RDWR | O_NOCTTY);
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if (inner == -1)
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FAIL_EXIT1 ("%s: %s", namebuf, strerror (errno));
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}
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if (termp)
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{
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if (tcsetattr (inner, TCSAFLUSH, termp))
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FAIL_EXIT1 ("tcsetattr: %s", strerror (errno));
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}
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#ifdef TIOCSWINSZ
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if (winp)
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{
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if (ioctl (inner, TIOCSWINSZ, winp))
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FAIL_EXIT1 ("TIOCSWINSZ: %s", strerror (errno));
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}
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#endif
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if (a_name)
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{
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if (!namebuf)
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namebuf = xptsname (outer);
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*a_name = namebuf;
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}
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else
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free (namebuf);
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*a_outer = outer;
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*a_inner = inner;
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}
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