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# Check prerequisites for compiling lib/c-stack.c.
# 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.
AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
[# for STACK_DIRECTION
AC_REQUIRE([AC_FUNC_ALLOCA])
AC_CACHE_CHECK([for working C stack overflow detection],
ac_cv_sys_xsi_stack_overflow_heuristic,
[AC_TRY_RUN(
[
#include <signal.h>
#include <ucontext.h>
static union
{
char buffer[SIGSTKSZ];
long double ld;
long u;
void *p;
} alternate_signal_stack;
#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
static void
segv_handler (int signo, siginfo_t *info, void *context)
{
if (0 < info->si_code)
{
ucontext_t const *user_context = context;
char const *stack_min = user_context->uc_stack.ss_sp;
size_t stack_size = user_context->uc_stack.ss_size;
char const *faulting_address = info->si_addr;
size_t s = faulting_address - stack_min;
size_t page_size = sysconf (_SC_PAGESIZE);
if (find_stack_direction (0) < 0)
s += page_size;
if (s < stack_size + page_size)
_exit (0);
}
_exit (1);
}
static int
c_stack_action (void)
{
stack_t st;
struct sigaction act;
int r;
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;
sigemptyset (&act.sa_mask);
act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
act.sa_sigaction = segv_handler;
return sigaction (SIGSEGV, &act, 0);
}
static int
recurse (char *p)
{
char array[500];
array[0] = 1;
return *p + recurse (array);
}
int
main (void)
{
c_stack_action ();
return recurse ("\1");
}
],
[ac_cv_sys_xsi_stack_overflow_heuristic=yes],
[ac_cv_sys_xsi_stack_overflow_heuristic=no],
[ac_cv_sys_xsi_stack_overflow_heuristic=cross-compiling])])
if test $ac_cv_sys_xsi_stack_overflow_heuristic = yes; then
AC_DEFINE(HAVE_XSI_STACK_OVERFLOW_HEURISTIC, 1,
[Define to 1 if extending the stack slightly past the limit causes
a SIGSEGV, and an alternate stack can be established with sigaltstack,
and the signal handler is passed a context that specifies the
run time stack. This behavior is defined by POSIX 1003.1-2001
with the X/Open System Interface (XSI) option
and is a standardized way to implement a SEGV-based stack
overflow detection heuristic.])
fi])
AC_DEFUN([jm_PREREQ_C_STACK],
[AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC])
# for STACK_DIRECTION
AC_REQUIRE([AC_FUNC_ALLOCA])
AC_CHECK_FUNCS(getcontext sigaltstack)
AC_CHECK_DECLS([getcontext], , , [#include <ucontext.h>])
AC_CHECK_DECLS([sigaltstack], , , [#include <signal.h>])
AC_CHECK_HEADERS(sys/resource.h ucontext.h unistd.h)
AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])])
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