Re: [PATCH] btrace, gdbserver: check btrace target pointers

[Yao Qi <qiyaoltc@gmail.com>]

Markus Metzger <markus.t.metzger@intel.com> writes:

> -#define target_enable_btrace(ptid, conf) \
> -  (*the_target->enable_btrace) (ptid, conf)
> +static inline struct btrace_target_info *
> +target_enable_btrace (ptid_t ptid, const struct btrace_config *conf)
> +{
> +  if (the_target->enable_btrace == nullptr)
> +    error ("Target does not support branch tracing.");
> +
> +  return (*the_target->enable_btrace) (ptid, conf);
> +}

It is reasonable to me that (*the_target->enable_btrace) may throw
various exceptions due to different reasons, but I am not convinced that
we should error on (the_target->enable_btrace == nullptr).  I don't like
replacing control flow logic with exception.  This is my personal
flavor.  Instead, can we check
(the_target->enable_btrace == nullptr) before using
target_enable_btrace, and error in handle_btrace_general_set if
thread->btrace is NULL.  What do you think?

-- 
Yao (齐尧)