+dnl #
+dnl # 3. allow decision to be overridden by user
+dnl #
+
+AC_MSG_CHECKING(what kind of backend should we use)
+
+AC_ARG_WITH(pthread, [ --with-pthread Use pthread instead of ucontext.],with_context=pthread)
+AC_ARG_WITH(pthread, [ --with-pthreads Use pthread instead of ucontext.],with_context=pthread)
+
+AC_ARG_WITH(context,
+ [ --with-context=[ucontext/pthread] Use either (System V) swapcontext or pthread [[default=auto]].],,
+ with_context=auto)
+
+if test "x$with_context$mcsc" = "xucontextno" ; then
+ AC_MSG_ERROR([--with-context=ucontext specified but ucontext unusable. Relaunch configure without this argument.], 77)
+fi
+
+case $with_context in
+ ucontext) ;;
+ pthread) ;;
+ pthreads) ;;
+ windows) ;;
+ auto) with_context=ucontext;;
+ *) AC_MSG_ERROR([--with-context must be either ucontext or pthread]) ;;
+esac
+
+if test "x$with_context" = "xucontext" ; then
+ if test ".$mcsc" = .yes; then
+ AC_MSG_RESULT(found working ucontext. Great!)
+ AC_DEFINE([CONTEXT_UCONTEXT],1,[Define if xbt contexts are based on ucontext or not])
+ else
+ if test ".$windows_context" = .yes ; then
+ AC_MSG_RESULT(use windows context portability layer.)
+ with_context=windows
+ else
+ AC_MSG_RESULT([[no working ucontext found. Try pthreads as a fallback]])
+ with_context=pthread
+ fi
+ fi
+fi
+
+if test "x$with_context" = "xpthreads"; then
+ with_context=pthread
+fi
+if test "x$with_context" = "xpthread"; then
+ AC_CHECK_HEADERS([pthread.h])
+ AC_CHECK_LIB(pthread,pthread_create,,
+ [AC_MSG_ERROR([[Cannot find pthreads (try --with-context=ucontext if you haven't already tried).]])])
+ AC_DEFINE([CONTEXT_THREADS],1,[Define if xbt contexts are based on our threads implementation or not])
+ AC_MSG_RESULT(You have pthreads. Let's use them.)
+fi
+
+dnl #
+dnl # 4. determine a few additional details
+dnl #
+
+if test "x$with_context" = "xucontext" ; then
+dnl # direction of stack grow
+ AC_CHECK_STACKGROWTH(PTH_STACKGROWTH)
+ if test ".$ac_cv_check_stackgrowth" = ".down"; then
+ PTH_STACK_GROWTH="down"
+ else
+ PTH_STACK_GROWTH="up"
+ fi
+ AC_SUBST(PTH_STACK_GROWTH)
+
+ AC_CHECK_STACKSETUP(makecontext, pth_skaddr_makecontext, pth_sksize_makecontext)
+fi
+
+#########################################
+## Check for libraries extra-dependencies
+##
+
+SG_CONFIGURE_PART(Checking extra libraries dependencies...)
+
+SIMGRID_DEP=""