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getopt can print a whole bunch of error messages, and when used standalone (from gnulib) it uses fprintf to do that. But fprintf is a cancellation point and getopt isn't, and also applying fprintf to a stream in wide-character mode is not allowed. glibc has an internal function called __fxprintf that writes a narrow format string to a stream regardless of mode, but it only handles ASCII format strings, and it's still a cancellation point. getopt's messages are translated, so they might not be ASCII. So getopt has an error message to an asprintf buffer, monkeys with internal flag bits on stderr to disable cancellation, and then calls __fxprintf(stderr, "%s", buffer). There isn't even a helper function, the code is duplicated every time. This patch fixes __fxprintf to handle arbitrary multibyte format strings, and adds a variant __fxprintf_nocancel that does the same thing but also isn't a cancellation point. (It still _works_ by monkeying with internal flag bits on the FILE, but that's not really a layering violation for code in stdio-common.) All of the #ifdef _LIBC blocks can then be reduced to their standalone versions with a little help from some macros at the top of the file. I also wrote a test case to verify that getopt really isn't a cancellation point, and I'm glad I did, because it found two bugs, one of which wasn't even to do with cancellation (see previous patch). * stdio-common/fxprintf.c (__fxprintf_nocancel): New function. (locked_vfxprintf): New helper function. Handle arbitrary multibyte strings, not just ASCII. * include/stdio.h: Declare __fxprintf_nocancel. * posix/getopt.c: When _LIBC is defined, define fprintf to __fxprintf_nocancel, flockfile to _IO_flockfile, and funlockfile to _IO_funlockfile. When neither _LIBC nor _POSIX_THREAD_SAFE_FUNCTIONS is defined, define flockfile and funlockfile as no-ops. (_getopt_internal_r): Remove all internal #ifdef _LIBC blocks; the standalone error-printing code can now be used for libc as well. Add an flockfile/funlockfile pair around one case where the error message is printed in several chunks. Don't use fputc. * posix/tst-getopt-cancel.c: New test. * posix/Makefile: Run it.
100 lines
2.4 KiB
C
100 lines
2.4 KiB
C
/* Copyright (C) 2005-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@gnu.org>.
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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 <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <wchar.h>
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#include <libioP.h>
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static int
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locked_vfxprintf (FILE *fp, const char *fmt, va_list ap)
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{
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if (_IO_fwide (fp, 0) <= 0)
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return _IO_vfprintf (fp, fmt, ap);
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/* We must convert the narrow format string to a wide one.
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Each byte can produce at most one wide character. */
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wchar_t *wfmt;
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mbstate_t mbstate;
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int res;
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int used_malloc = 0;
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size_t len = strlen (fmt) + 1;
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if (__glibc_unlikely (len > SIZE_MAX / sizeof (wchar_t)))
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{
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__set_errno (EOVERFLOW);
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return -1;
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}
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if (__libc_use_alloca (len * sizeof (wchar_t)))
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wfmt = alloca (len * sizeof (wchar_t));
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else if ((wfmt = malloc (len * sizeof (wchar_t))) == NULL)
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return -1;
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else
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used_malloc = 1;
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memset (&mbstate, 0, sizeof mbstate);
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res = __mbsrtowcs (wfmt, &fmt, len, &mbstate);
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if (res != -1)
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res = _IO_vfwprintf (fp, wfmt, ap);
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if (used_malloc)
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free (wfmt);
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return res;
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}
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int
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__fxprintf (FILE *fp, const char *fmt, ...)
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{
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if (fp == NULL)
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fp = stderr;
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va_list ap;
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va_start (ap, fmt);
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_IO_flockfile (fp);
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int res = locked_vfxprintf (fp, fmt, ap);
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_IO_funlockfile (fp);
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va_end (ap);
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return res;
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}
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int
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__fxprintf_nocancel (FILE *fp, const char *fmt, ...)
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{
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if (fp == NULL)
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fp = stderr;
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va_list ap;
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va_start (ap, fmt);
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_IO_flockfile (fp);
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int save_flags2 = ((_IO_FILE *)fp)->_flags2;
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((_IO_FILE *)fp)->_flags2 |= _IO_FLAGS2_NOTCANCEL;
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int res = locked_vfxprintf (fp, fmt, ap);
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((_IO_FILE *)fp)->_flags2 = save_flags2;
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_IO_funlockfile (fp);
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va_end (ap);
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return res;
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}
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