+ void *stack = xbt_malloc0(smx_context_stack_size);
+
+#ifdef HAVE_VALGRIND_VALGRIND_H
+ unsigned int valgrind_stack_id =
+ VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
+ memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
+ sizeof valgrind_stack_id);
+#endif
+
+ return stack;