m4/sigaltstack.m4

# sigaltstack.m4
# serial 17
dnl Copyright (C) 2002-2026 Free Software Foundation, Inc.
dnl This file is free software, distributed under the terms of the GNU
dnl General Public License as published by the Free Software Foundation;
dnl either version 2 of the License, or (at your option) any later version.
dnl As a special exception to the GNU General Public License, this file
dnl may be distributed as part of a program that contains a configuration
dnl script generated by Autoconf, under the same distribution terms as
dnl the rest of that program.

dnl Written by Bruno Haible and Eric Blake.

AC_DEFUN([SV_SIGALTSTACK],
[
  AC_REQUIRE([AC_PROG_CC])
  AC_REQUIRE([AC_CANONICAL_HOST])

  AC_CHECK_FUNCS_ONCE([sigaltstack setrlimit])

  if test "$ac_cv_func_sigaltstack" = yes; then
    AC_CHECK_TYPE([stack_t], ,
      [AC_DEFINE(stack_t, [struct sigaltstack],
         [Define to 'struct sigaltstack' if that's the type of the argument to sigaltstack])
      ],
      [
#include <signal.h>
#if HAVE_SYS_SIGNAL_H
# include <sys/signal.h>
#endif
      ])
  fi

  AC_CACHE_CHECK([for working sigaltstack], [sv_cv_sigaltstack], [
    if test "$ac_cv_func_sigaltstack" = yes; then
      case "$host_os" in
        macos* | darwin[[6-9]]* | darwin[[1-9]][[0-9]]*)
          # On MacOS X 10.2 or newer, just assume that if it compiles, it will
          # work. If we were to perform the real test, 1 Crash Report dialog
          # window would pop up.
          AC_LINK_IFELSE([
            AC_LANG_PROGRAM([[#include <signal.h>]],
              [[int x = SA_ONSTACK; stack_t ss; sigaltstack ((stack_t*)0, &ss);]])],
            [sv_cv_sigaltstack="guessing yes"],
            [sv_cv_sigaltstack=no])
          ;;
        *)
          AC_RUN_IFELSE([
            AC_LANG_SOURCE([[
#include <stdlib.h>
#include <signal.h>
#if HAVE_SYS_SIGNAL_H
# include <sys/signal.h>
#endif
#if HAVE_SETRLIMIT
# include <sys/types.h>
# include <sys/time.h>
# include <sys/resource.h>
#endif
void stackoverflow_handler (int sig)
{
  /* If we get here, the stack overflow was caught.  */
  exit (0);
}
volatile int * recurse_1 (volatile int n, volatile int *p)
{
  if (n >= 0)
    *recurse_1 (n + 1, p) += n;
  return p;
}
int recurse (volatile int n)
{
  int sum = 0;
  return *recurse_1 (n, &sum);
}
char mystack[2 * (1 << 24)];
int main ()
{
  stack_t altstack;
  struct sigaction action;
#if defined HAVE_SETRLIMIT && defined RLIMIT_STACK
  /* Before starting the endless recursion, try to be friendly to the user's
     machine.  On some Linux 2.2.x systems, there is no stack limit for user
     processes at all.  We don't want to kill such systems.  */
  struct rlimit rl;
  rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
  setrlimit (RLIMIT_STACK, &rl);
#endif
  /* Install the alternate stack.  */
#ifdef SIGSTKSZ
  if (sizeof mystack < SIGSTKSZ)
    exit (3);
#endif
  altstack.ss_sp = mystack;
  altstack.ss_size = sizeof mystack;
  altstack.ss_flags = 0; /* no SS_DISABLE */
  if (sigaltstack (&altstack, NULL) < 0)
    exit (1);
  /* Install the SIGSEGV handler.  */
  sigemptyset (&action.sa_mask);
  action.sa_handler = &stackoverflow_handler;
  action.sa_flags = SA_ONSTACK;
  sigaction (SIGSEGV, &action, (struct sigaction *) NULL);
  sigaction (SIGBUS, &action, (struct sigaction *) NULL);
  /* Provoke a stack overflow.  */
  recurse (0);
  exit (2);
}]])],
            [sv_cv_sigaltstack=yes],
            [sv_cv_sigaltstack=no],
            [
              dnl FIXME: Put in some more known values here.
              case "$host_os" in
                *)
                  AC_LINK_IFELSE([
                    AC_LANG_PROGRAM([[#include <signal.h>]],
                      [[int x = SA_ONSTACK; stack_t ss; sigaltstack ((stack_t*)0, &ss);]])],
                    [sv_cv_sigaltstack="guessing yes"],
                    [sv_cv_sigaltstack=no])
                  ;;
              esac
            ])
          ;;
      esac
    else
      sv_cv_sigaltstack=no
    fi
  ])
  if test "$sv_cv_sigaltstack" != no; then
    AC_DEFINE([HAVE_WORKING_SIGALTSTACK], [1],
      [Define if you have the sigaltstack() function and it works.])
  fi
])