312 lines
8.1 KiB
C
312 lines
8.1 KiB
C
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/* Stack overflow handling.
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Copyright (C) 2002, 2004 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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/* Written by Paul Eggert. */
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/* NOTES:
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A program that uses alloca, dynamic arrays, or large local
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variables may extend the stack by more than a page at a time. If
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so, when the stack overflows the operating system may not detect
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the overflow until the program uses the array, and this module may
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incorrectly report a program error instead of a stack overflow.
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To avoid this problem, allocate only small objects on the stack; a
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program should be OK if it limits single allocations to a page or
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less. Allocate larger arrays in static storage, or on the heap
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(e.g., with malloc). Yes, this is a pain, but we don't know of any
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better solution that is portable.
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No attempt has been made to deal with multithreaded applications. */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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#ifndef __attribute__
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# if __GNUC__ < 3 || __STRICT_ANSI__
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# define __attribute__(x)
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# endif
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#endif
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#include "gettext.h"
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#define _(msgid) gettext (msgid)
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#include <errno.h>
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#ifndef ENOTSUP
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# define ENOTSUP EINVAL
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#endif
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#ifndef EOVERFLOW
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# define EOVERFLOW EINVAL
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#endif
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#include <signal.h>
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#if ! HAVE_STACK_T && ! defined stack_t
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typedef struct sigaltstack stack_t;
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#endif
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#include <stdlib.h>
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#include <string.h>
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#if HAVE_SYS_RESOURCE_H
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/* Include sys/time.h here, because...
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SunOS-4.1.x <sys/resource.h> fails to include <sys/time.h>.
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This gives "incomplete type" errors for ru_utime and tu_stime. */
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# if HAVE_SYS_TIME_H
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# include <sys/time.h>
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# endif
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# include <sys/resource.h>
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#endif
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#if HAVE_UCONTEXT_H
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# include <ucontext.h>
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#endif
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#if HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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#ifndef STDERR_FILENO
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# define STDERR_FILENO 2
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#endif
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#if DEBUG
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# include <stdio.h>
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#endif
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#include "c-stack.h"
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#include "exitfail.h"
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#if (HAVE_STRUCT_SIGACTION_SA_SIGACTION && defined SA_NODEFER \
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&& defined SA_ONSTACK && defined SA_RESETHAND && defined SA_SIGINFO)
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# define SIGACTION_WORKS 1
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#else
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# define SIGACTION_WORKS 0
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#endif
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extern char *program_name;
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/* The user-specified action to take when a SEGV-related program error
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or stack overflow occurs. */
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static void (* volatile segv_action) (int);
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/* Translated messages for program errors and stack overflow. Do not
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translate them in the signal handler, since gettext is not
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async-signal-safe. */
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static char const * volatile program_error_message;
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static char const * volatile stack_overflow_message;
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/* Output an error message, then exit with status EXIT_FAILURE if it
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appears to have been a stack overflow, or with a core dump
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otherwise. This function is async-signal-safe. */
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static void die (int) __attribute__ ((noreturn));
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static void
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die (int signo)
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{
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char const *message;
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segv_action (signo);
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message = signo ? program_error_message : stack_overflow_message;
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write (STDERR_FILENO, program_name, strlen (program_name));
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write (STDERR_FILENO, ": ", 2);
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write (STDERR_FILENO, message, strlen (message));
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write (STDERR_FILENO, "\n", 1);
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if (! signo)
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_exit (exit_failure);
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kill (getpid (), signo);
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abort ();
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}
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#if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
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/* Direction of the C runtime stack. This function is
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async-signal-safe. */
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# if STACK_DIRECTION
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# define find_stack_direction(ptr) STACK_DIRECTION
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# else
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static int
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find_stack_direction (char const *addr)
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{
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char dummy;
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return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
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}
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# endif
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/* Storage for the alternate signal stack. */
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static union
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{
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char buffer[SIGSTKSZ];
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/* These other members are for proper alignment. There's no
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standard way to guarantee stack alignment, but this seems enough
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in practice. */
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long double ld;
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long l;
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void *p;
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} alternate_signal_stack;
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# if SIGACTION_WORKS
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/* Handle a segmentation violation and exit. This function is
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async-signal-safe. */
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static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
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static void
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segv_handler (int signo, siginfo_t *info,
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void *context __attribute__ ((unused)))
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{
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/* Clear SIGNO if it seems to have been a stack overflow. */
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if (0 < info->si_code)
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{
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# if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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/* We can't easily determine whether it is a stack overflow; so
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assume that the rest of our program is perfect (!) and that
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this segmentation violation is a stack overflow. */
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signo = 0;
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# else
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/* If the faulting address is within the stack, or within one
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page of the stack end, assume that it is a stack
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overflow. */
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ucontext_t const *user_context = context;
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char const *stack_base = user_context->uc_stack.ss_sp;
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size_t stack_size = user_context->uc_stack.ss_size;
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char const *faulting_address = info->si_addr;
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size_t s = faulting_address - stack_base;
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size_t page_size = sysconf (_SC_PAGESIZE);
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if (find_stack_direction (0) < 0)
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s += page_size;
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if (s < stack_size + page_size)
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signo = 0;
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# if DEBUG
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{
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char buf[1024];
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sprintf (buf,
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"segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
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faulting_address, stack_base, (unsigned long) stack_size,
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(unsigned long) page_size, signo);
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write (STDERR_FILENO, buf, strlen (buf));
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}
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# endif
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# endif
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}
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die (signo);
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}
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# endif
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static void
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null_action (int signo __attribute__ ((unused)))
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{
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}
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/* Set up ACTION so that it is invoked on C stack overflow. Return -1
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(setting errno) if this cannot be done.
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When ACTION is called, it is passed an argument equal to SIGSEGV
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for a segmentation violation that does not appear related to stack
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overflow, and is passed zero otherwise. On many platforms it is
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hard to tell; when in doubt, zero is passed.
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A null ACTION acts like an action that does nothing.
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ACTION must be async-signal-safe. ACTION together with its callees
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must not require more than SIGSTKSZ bytes of stack space. */
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int
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c_stack_action (void (*action) (int))
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{
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int r;
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stack_t st;
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st.ss_flags = 0;
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st.ss_sp = alternate_signal_stack.buffer;
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st.ss_size = sizeof alternate_signal_stack.buffer;
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r = sigaltstack (&st, 0);
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if (r != 0)
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return r;
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segv_action = action ? action : null_action;
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program_error_message = _("program error");
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stack_overflow_message = _("stack overflow");
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{
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# if SIGACTION_WORKS
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struct sigaction act;
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sigemptyset (&act.sa_mask);
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/* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
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this is not true on Solaris 8 at least. It doesn't hurt to use
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SA_NODEFER here, so leave it in. */
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act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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act.sa_sigaction = segv_handler;
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return sigaction (SIGSEGV, &act, 0);
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# else
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return signal (SIGSEGV, die) == SIG_ERR ? -1 : 0;
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# endif
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}
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}
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#else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */
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int
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c_stack_action (void (*action) (int) __attribute__ ((unused)))
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{
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errno = ENOTSUP;
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return -1;
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}
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#endif
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#if DEBUG
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int volatile exit_failure;
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static long
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recurse (char *p)
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{
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char array[500];
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array[0] = 1;
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return *p + recurse (array);
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}
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char *program_name;
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int
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main (int argc __attribute__ ((unused)), char **argv)
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{
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program_name = argv[0];
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fprintf (stderr,
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"The last output line should contain \"stack overflow\".\n");
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if (c_stack_action (0) == 0)
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return recurse ("\1");
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perror ("c_stack_action");
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return 1;
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}
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#endif /* DEBUG */
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/*
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Local Variables:
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compile-command: "gcc -DDEBUG -DHAVE_CONFIG_H -I.. -g -O -Wall -W c-stack.c"
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End:
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*/
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