From 2cc7bad0ae0a412e75270be5ed41d45c03e7a931 Mon Sep 17 00:00:00 2001 From: Zack Weinberg Date: Wed, 21 Feb 2018 19:12:51 -0500 Subject: [BZ 1190] Make EOF sticky in stdio. 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. --- support/support_openpty.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 support/support_openpty.c (limited to 'support/support_openpty.c') diff --git a/support/support_openpty.c b/support/support_openpty.c new file mode 100644 index 0000000000..ac779ab91e --- /dev/null +++ b/support/support_openpty.c @@ -0,0 +1,109 @@ +/* Open a pseudoterminal. + Copyright (C) 2018 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include + +#include +#include +#include + +#include +#include +#include +#include + +/* As ptsname, but allocates space for an appropriately-sized string + using malloc. */ +static char * +xptsname (int fd) +{ + int rv; + size_t buf_len = 128; + char *buf = xmalloc (buf_len); + for (;;) + { + rv = ptsname_r (fd, buf, buf_len); + if (rv) + FAIL_EXIT1 ("ptsname_r: %s", strerror (errno)); + + if (memchr (buf, '\0', buf_len)) + return buf; /* ptsname succeeded and the buffer was not truncated */ + + buf_len *= 2; + buf = xrealloc (buf, buf_len); + } +} + +void +support_openpty (int *a_outer, int *a_inner, char **a_name, + const struct termios *termp, + const struct winsize *winp) +{ + int outer = -1, inner = -1; + char *namebuf = 0; + + outer = posix_openpt (O_RDWR | O_NOCTTY); + if (outer == -1) + FAIL_EXIT1 ("posix_openpt: %s", strerror (errno)); + + if (grantpt (outer)) + FAIL_EXIT1 ("grantpt: %s", strerror (errno)); + + if (unlockpt (outer)) + FAIL_EXIT1 ("unlockpt: %s", strerror (errno)); + + +#ifdef TIOCGPTPEER + inner = ioctl (outer, TIOCGPTPEER, O_RDWR | O_NOCTTY); +#endif + if (inner == -1) + { + /* The kernel might not support TIOCGPTPEER, fall back to open + by name. */ + namebuf = xptsname (outer); + inner = open (namebuf, O_RDWR | O_NOCTTY); + if (inner == -1) + FAIL_EXIT1 ("%s: %s", namebuf, strerror (errno)); + } + + if (termp) + { + if (tcsetattr (inner, TCSAFLUSH, termp)) + FAIL_EXIT1 ("tcsetattr: %s", strerror (errno)); + } +#ifdef TIOCSWINSZ + if (winp) + { + if (ioctl (inner, TIOCSWINSZ, winp)) + FAIL_EXIT1 ("TIOCSWINSZ: %s", strerror (errno)); + } +#endif + + if (a_name) + { + if (!namebuf) + namebuf = xptsname (outer); + *a_name = namebuf; + } + else + free (namebuf); + *a_outer = outer; + *a_inner = inner; +} -- cgit 1.4.1