On 10/16/2014 11:16 PM, Pekka Paalanen wrote:
...adding a function int/bool wl_is_wl_display_pointer(void *p) into
libwayland-client.so. As that function would be built into
libwayland-client.so, it naturally uses the client.so version of
wl_display_interface symbol (unless dynamic linking miraculously
manages to mess that up?).
'p' would be the tentative 'struct wl_display *', so that the
implementation details of struct wl_display would be contained in
libwayland-client.so, and not leaked elsewhere like e.g. in Mesa.
Might be better if the function was more like a cast. It returns either
(wl_display*)p or NULL depending on the test. The reason is so the user
can just assign it to a correct pointer without doing the cast
themselves. This might be important if more of these casts are added in
the future, it makes it harder to accidentally run the wrong test for
the cast you want to do:
struct wl_display* wl_display_dynamic_cast (void* p) {
if (test(p)) return (struct wl_display*)p;
else return 0;
}
I am unsure about the exact definition of wl_is_wl_display_pointer():
can it do the dereferencability check itself, or should we require the
caller to guarantee that dereferencing cannot crash. The latter would
leave the portability burden on the callers rather than libwayland.
Probably it should handle NULL.
Maybe it should check alignment if wl_display has stricter alignment
restrictions than some other plausable arguments.
It does not seem to me that a check for pointing to valid memory is
necessary.
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