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authorZack Weinberg <zackw@panix.com>2018-02-21 19:12:51 -0500
committerZack Weinberg <zackw@panix.com>2018-03-13 08:31:56 -0400
commit2cc7bad0ae0a412e75270be5ed41d45c03e7a931 (patch)
treea726dff1dc98e5fabf47685d10f9c681265db95b /support
parent778f1974863d63e858b6d0105e41d6f0c30732d3 (diff)
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[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.
Diffstat (limited to 'support')
-rw-r--r--support/Makefile1
-rw-r--r--support/support_openpty.c109
-rw-r--r--support/tty.h45
3 files changed, 155 insertions, 0 deletions
diff --git a/support/Makefile b/support/Makefile
index 1bda81e..c632df6 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -52,6 +52,7 @@ libsupport-routines = \
support_format_hostent \
support_format_netent \
support_isolate_in_subprocess \
+ support_openpty \
support_record_failure \
support_run_diff \
support_shared_allocate \
diff --git a/support/support_openpty.c b/support/support_openpty.c
new file mode 100644
index 0000000..ac779ab
--- /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
+ <http://www.gnu.org/licenses/>. */
+
+#include <support/tty.h>
+#include <support/check.h>
+#include <support/support.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <fcntl.h>
+#include <termios.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+/* 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;
+}
diff --git a/support/tty.h b/support/tty.h
new file mode 100644
index 0000000..1d37c42
--- /dev/null
+++ b/support/tty.h
@@ -0,0 +1,45 @@
+/* Support functions related to (pseudo)terminals.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _SUPPORT_TTY_H
+#define _SUPPORT_TTY_H 1
+
+struct termios;
+struct winsize;
+
+/** Open a pseudoterminal pair. The outer fd is written to the address
+ A_OUTER and the inner fd to A_INNER.
+
+ If A_NAME is not NULL, it will be set to point to a string naming
+ the /dev/pts/NNN device corresponding to the inner fd; space for
+ this string is allocated with malloc and should be freed by the
+ caller when no longer needed. (This is different from the libutil
+ function 'openpty'.)
+
+ If TERMP is not NULL, the terminal parameters will be initialized
+ according to the termios structure it points to.
+
+ If WINP is not NULL, the terminal window size will be set
+ accordingly.
+
+ Terminates the process on failure (like xmalloc). */
+extern void support_openpty (int *a_outer, int *a_inner, char **a_name,
+ const struct termios *termp,
+ const struct winsize *winp);
+
+#endif