asterisk/autoconf/ast_func_fork.m4

# AST_FUNC_FORK
# -------------
AN_FUNCTION([fork],  [AST_FUNC_FORK])
AN_FUNCTION([vfork], [AST_FUNC_FORK])
AC_DEFUN([AST_FUNC_FORK],
[AC_REQUIRE([AC_TYPE_PID_T])dnl
AC_CHECK_HEADERS(vfork.h)
AC_CHECK_FUNCS(fork vfork)
if test "x$ac_cv_func_fork" = xyes; then
  _AST_FUNC_FORK
else
  ac_cv_func_fork_works=$ac_cv_func_fork
fi
if test "x$ac_cv_func_fork_works" = xcross; then
  case $host in
    *-*-amigaos* | *-*-msdosdjgpp* | *-*-uclinux* )
      # Override, as these systems have only a dummy fork() stub
      ac_cv_func_fork_works=no
      ;;
    *)
      ac_cv_func_fork_works=yes
      ;;
  esac
  AC_MSG_WARN([result $ac_cv_func_fork_works guessed because of cross compilation])
fi
ac_cv_func_vfork_works=$ac_cv_func_vfork
if test "x$ac_cv_func_vfork" = xyes; then
  _AC_FUNC_VFORK
fi;
if test "x$ac_cv_func_fork_works" = xcross; then
  ac_cv_func_vfork_works=$ac_cv_func_vfork
  AC_MSG_WARN([result $ac_cv_func_vfork_works guessed because of cross compilation])
fi

if test "x$ac_cv_func_vfork_works" = xyes; then
  AC_DEFINE(HAVE_WORKING_VFORK, 1, [Define to 1 if `vfork' works.])
else
  AC_DEFINE(vfork, fork, [Define as `fork' if `vfork' does not work.])
fi
if test "x$ac_cv_func_fork_works" = xyes; then
  AC_DEFINE(HAVE_WORKING_FORK, 1, [Define to 1 if `fork' works.])
  PBX_WORKING_FORK=1
  AC_SUBST(PBX_WORKING_FORK)
fi
])# AST_FUNC_FORK


# _AST_FUNC_FORK
# -------------
AC_DEFUN([_AST_FUNC_FORK],
  [AC_CACHE_CHECK(for working fork, ac_cv_func_fork_works,
    [AC_RUN_IFELSE(
      [AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
	[
	  /* By Ruediger Kuhlmann. */
	  return fork () < 0;
	])],
      [ac_cv_func_fork_works=yes],
      [ac_cv_func_fork_works=no],
      [ac_cv_func_fork_works=cross])])]
)# _AST_FUNC_FORK