On 20/02/18 10:17, Marc Lehmann wrote:
On Tue, Feb 20, 2018 at 12:40:38AM +0800, Andy Green <a...@warmcat.com> wrote:
You sound confident about that, but actually having implemented it, you have
not considered that the structures composing event lib state (handles, loop
objects etc) must be defined in one place with types available for all event
libs simultaneously.
Not really, even C supports opaque types.
No, there is no "not really" about it.
C supports opaque type pointers because the size of a pointer is known
regardless of the details of what it points to.
However you cannot compose an opaque / forward-referenced struct into
another struct with type safety, because the size of the undefined thing
is unknown.
For example you do this:
typedef struct ev_io
{
EV_WATCHER_LIST (ev_io)
int fd; /* ro */
int events; /* ro */
} ev_io;
and I do this
struct lws_io_watcher {
#ifdef LWS_WITH_LIBEV
ev_io ev_watcher;
#endif
#ifdef LWS_WITH_LIBUV
uv_poll_t uv_watcher;
#endif
#ifdef LWS_WITH_LIBEVENT
struct event *event_watcher;
#endif
struct lws_context *context;
uint8_t actual_events;
};
I must have your struct definition and that means I must have your headers.
-Andy
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