new file mode 100644
--- /dev/null
+++ b/lib/c-stack.c
@@ -0,0 +1,429 @@
+/* Stack overflow handling.
+
+   Copyright (C) 2002 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Written by Paul Eggert.  */
+
+/* NOTES:
+
+   A program that uses alloca, dynamic arrays, or large local
+   variables may extend the stack by more than a page at a time.  If
+   so, when the stack overflows the operating system may not detect
+   the overflow until the program uses the array, and this module may
+   incorrectly report a program error instead of a stack overflow.
+
+   To avoid this problem, allocate only small objects on the stack; a
+   program should be OK if it limits single allocations to a page or
+   less.  Allocate larger arrays in static storage, or on the heap
+   (e.g., with malloc).  Yes, this is a pain, but we don't know of any
+   better solution that is portable.
+
+   No attempt has been made to deal with multithreaded applications.
+
+   If ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC, the current implementation
+   assumes that, if the RLIMIT_STACK limit changes during execution,
+   then c_stack_action is invoked immediately afterwards.  */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#ifndef __attribute__
+# if __GNUC__ < 3 || __STRICT_ANSI__
+#  define __attribute__(x)
+# endif
+#endif
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+#include <errno.h>
+#ifndef ENOTSUP
+# define ENOTSUP EINVAL
+#endif
+#ifndef EOVERFLOW
+# define EOVERFLOW EINVAL
+#endif
+
+#include <signal.h>
+#if ! HAVE_STACK_T && ! defined stack_t
+typedef struct sigaltstack stack_t;
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+
+#if HAVE_SYS_RESOURCE_H
+# include <sys/resource.h>
+#endif
+
+#if HAVE_UCONTEXT_H
+# include <ucontext.h>
+#endif
+
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+#ifndef STDERR_FILENO
+# define STDERR_FILENO 2
+#endif
+
+#if DEBUG
+# include <stdio.h>
+#endif
+
+#include "c-stack.h"
+#include "exitfail.h"
+
+extern char *program_name;
+
+/* The user-specified action to take when a SEGV-related program error
+   or stack overflow occurs.  */
+static void (* volatile segv_action) (int);
+
+/* Translated messages for program errors and stack overflow.  Do not
+   translate them in the signal handler, since gettext is not
+   async-signal-safe.  */
+static char const * volatile program_error_message;
+static char const * volatile stack_overflow_message;
+
+/* Output an error message, then exit with status EXIT_FAILURE if it
+   appears to have been a stack overflow, or with a core dump
+   otherwise.  This function is async-signal-safe.  */
+
+static void die (int) __attribute__ ((noreturn));
+static void
+die (int signo)
+{
+  char const *message =
+    signo ? program_error_message : stack_overflow_message;
+  segv_action (signo);
+  write (STDERR_FILENO, program_name, strlen (program_name));
+  write (STDERR_FILENO, ": ", 2);
+  write (STDERR_FILENO, message, strlen (message));
+  write (STDERR_FILENO, "\n", 1);
+  if (! signo)
+    _exit (exit_failure);
+  kill (getpid (), signo);
+  abort ();
+}
+
+#if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
+
+/* Direction of the C runtime stack.  This function is
+   async-signal-safe.  */
+
+# if STACK_DIRECTION
+#  define find_stack_direction(ptr) STACK_DIRECTION
+# else
+static int
+find_stack_direction (char const *addr)
+{
+  char dummy;
+  return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
+}
+# endif
+
+# if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
+#  define get_stack_location(argv) 0
+# else
+
+#  if defined RLIMIT_STACK && defined _SC_PAGESIZE
+
+/* Return the minimum machine address deducible from ARGV.  This
+   includes the addresses of all the strings that ARGV points at, as
+   well as the address of ARGV itself.  */
+
+static char const *
+min_address_from_argv (char * const *argv)
+{
+  char const *min = (char const *) argv;
+  char const *p;
+  while ((p = *argv++))
+    if (p < min)
+      min = p;
+  return min;
+}
+
+/* Return the maximum machine address deducible from ARGV.  */
+
+static char const *
+max_address_from_argv (char * const *argv)
+{
+  char const *max = *argv;
+  char const *max1;
+  char const *p;
+  while ((p = *argv++))
+    if (max < p)
+      max = p;
+  max1 = (char const *) (argv + 1);
+  return max && max1 < max ? max + strlen (max) + 1 : max1;
+}
+#  endif
+
+/* The base and size of the stack, determined at startup.  */
+static char const * volatile stack_base;
+static size_t volatile stack_size;
+
+/* Store the base and size of the stack into the static variables
+   STACK_BASE and STACK_SIZE.  The base is the numerically lowest
+   address in the stack.  Return -1 (setting errno) if this cannot be
+   done.  */
+
+static int
+get_stack_location (char * const *argv)
+{
+#  if ! (defined RLIMIT_STACK && defined _SC_PAGESIZE)
+
+  errno = ENOTSUP;
+  return -1;
+
+#  else
+
+  struct rlimit rlimit;
+  int r = getrlimit (RLIMIT_STACK, &rlimit);
+  if (r == 0)
+    {
+      char const *base;
+      size_t size = rlimit.rlim_cur;
+      extern char **environ;
+      size_t page_size = sysconf (_SC_PAGESIZE);
+      int stack_direction = find_stack_direction (0);
+
+#   if HAVE_GETCONTEXT && HAVE_DECL_GETCONTEXT
+      ucontext_t context;
+      if (getcontext (&context) == 0)
+	{
+	  base = context.uc_stack.ss_sp;
+	  if (stack_direction < 0)
+	    base -= size - context.uc_stack.ss_size;
+	}
+      else
+#   endif
+	{
+	  if (stack_direction < 0)
+	    {
+	      char const *a = max_address_from_argv (argv);
+	      char const *b = max_address_from_argv (environ);
+	      base = (a < b ? b : a) - size;
+	      base += - (size_t) base % page_size;
+	    }
+	  else
+	    {
+	      char const *a = min_address_from_argv (argv);
+	      char const *b = min_address_from_argv (environ);
+	      base = a < b ? a : b;
+	      base -= (size_t) base % page_size;
+	    }
+	}
+
+      if (size != rlimit.rlim_cur
+	  || rlimit.rlim_cur < 0
+	  || base + size < base
+#   ifdef RLIM_SAVED_CUR
+	  || rlimit.rlim_cur == RLIM_SAVED_CUR
+#   endif
+#   ifdef RLIM_SAVED_MAX
+	  || rlimit.rlim_cur == RLIM_SAVED_MAX
+#   endif
+#   ifdef RLIM_INFINITY
+	  || rlimit.rlim_cur == RLIM_INFINITY
+#   endif
+	  )
+	{
+	  errno = EOVERFLOW;
+	  return -1;
+	}
+
+      stack_base = base;
+      stack_size = size;
+
+#   if DEBUG
+      fprintf (stderr, "get_stack_location base=%p size=%lx\n",
+	       base, (unsigned long) size);
+#   endif
+    }
+
+  return r;
+
+#  endif
+}
+# endif
+
+/* Storage for the alternate signal stack.  */
+static union
+{
+  char buffer[SIGSTKSZ];
+
+  /* These other members are for proper alignment.  There's no
+     standard way to guarantee stack alignment, but this seems enough
+     in practice.  */
+  long double ld;
+  long l;
+  void *p;
+} alternate_signal_stack;
+
+# if defined SA_ONSTACK && defined _SC_PAGESIZE
+
+/* Handle a segmentation violation and exit.  This function is
+   async-signal-safe.  */
+
+static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
+static void
+segv_handler (int signo, siginfo_t *info,
+	      void *context __attribute__ ((unused)))
+{
+  /* Clear SIGNO if it seems to have been a stack overflow.  */
+  if (0 < info->si_code)
+    {
+      /* If the faulting address is within the stack, or within one
+	 page of the stack end, assume that it is a stack
+	 overflow.  */
+#  if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
+      ucontext_t const *user_context = context;
+      char const *stack_base = user_context->uc_stack.ss_sp;
+      size_t stack_size = user_context->uc_stack.ss_size;
+#  endif
+      char const *faulting_address = info->si_addr;
+      size_t s = faulting_address - stack_base;
+      size_t page_size = sysconf (_SC_PAGESIZE);
+      if (find_stack_direction (0) < 0)
+	s += page_size;
+      if (s < stack_size + page_size)
+	signo = 0;
+
+#  if DEBUG
+      {
+	char buf[1024];
+	sprintf (buf,
+		 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
+		 faulting_address, stack_base, (unsigned long) stack_size,
+		 (unsigned long) page_size, signo);
+	write (STDERR_FILENO, buf, strlen (buf));
+      }
+#  endif
+    }
+
+  die (signo);
+}
+# endif
+
+static void
+null_action (int signo __attribute__ ((unused)))
+{
+}
+
+/* Assuming ARGV is the argument vector of `main', set up ACTION so
+   that it is invoked on C stack overflow.  Return -1 (setting errno)
+   if this cannot be done.
+
+   When ACTION is called, it is passed an argument equal to SIGSEGV
+   for a segmentation violation that does not appear related to stack
+   overflow, and is passed zero otherwise.
+
+   A null ACTION acts like an action that does nothing.
+
+   ACTION must be async-signal-safe.  ACTION together with its callees
+   must not require more than SIGSTKSZ bytes of stack space.  */
+
+int
+c_stack_action (char * const *argv __attribute__ ((unused)),
+		void (*action) (int))
+{
+  int r = get_stack_location (argv);
+  if (r != 0)
+    return r;
+
+  {
+    stack_t st;
+    st.ss_flags = 0;
+    st.ss_sp = alternate_signal_stack.buffer;
+    st.ss_size = sizeof alternate_signal_stack.buffer;
+    r = sigaltstack (&st, 0);
+    if (r != 0)
+      return r;
+  }
+
+  segv_action = action ? action : null_action;
+  program_error_message = _("program error");
+  stack_overflow_message = _("stack overflow");
+
+  {
+# if ! (defined SA_ONSTACK && defined _SC_PAGESIZE)
+    return signal (SIGSEGV, die) == SIG_ERR ? -1 : 0;
+# else
+    struct sigaction act;
+    sigemptyset (&act.sa_mask);
+
+    /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
+       this is not true on Solaris 8 at least.  It doesn't hurt to use
+       SA_NODEFER here, so leave it in.  */
+    act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
+
+    act.sa_sigaction = segv_handler;
+
+    return sigaction (SIGSEGV, &act, 0);
+# endif
+  }
+}
+
+#else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */
+
+int
+c_stack_action (char * const *argv __attribute__ ((unused)),
+		void (*action) (int)  __attribute__ ((unused)))
+{
+  errno = ENOTSUP;
+  return -1;
+}
+
+#endif
+
+
+
+#if DEBUG
+
+int volatile exit_failure;
+
+static long
+recurse (char *p)
+{
+  char array[500];
+  array[0] = 1;
+  return *p + recurse (array);
+}
+
+char *program_name;
+
+int
+main (int argc __attribute__ ((unused)), char **argv)
+{
+  program_name = argv[0];
+  fprintf (stderr, "The last line of output should be \"stack overflow\".\n");
+  if (c_stack_action (argv, 0) == 0)
+    return recurse ("\1");
+  perror ("c_stack_action");
+  return 1;
+}
+
+#endif /* DEBUG */
+
+/*
+Local Variables:
+compile-command: "gcc -DDEBUG -DHAVE_CONFIG_H -I.. -g -O -Wall -W c-stack.c"
+End:
+*/

new file mode 100644
--- /dev/null
+++ b/lib/c-stack.h
@@ -0,0 +1,19 @@
+/* Stack overflow handling.
+
+   Copyright (C) 2002 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+int c_stack_action (char * const *, void (*) (int));