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author | Zack Weinberg <zackw@panix.com> | 2018-02-21 19:12:51 -0500 |
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committer | Zack Weinberg <zackw@panix.com> | 2018-03-13 08:31:56 -0400 |
commit | 2cc7bad0ae0a412e75270be5ed41d45c03e7a931 (patch) | |
tree | a726dff1dc98e5fabf47685d10f9c681265db95b /support/tty.h | |
parent | 778f1974863d63e858b6d0105e41d6f0c30732d3 (diff) | |
download | glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.zip glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.tar.gz glibc-2cc7bad0ae0a412e75270be5ed41d45c03e7a931.tar.bz2 |
[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/tty.h')
-rw-r--r-- | support/tty.h | 45 |
1 files changed, 45 insertions, 0 deletions
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 |