Hi,
When I include ev.h in my c++ code (gcc 4.9, -std=c++11 -Wall -Wextra
-Werror -pedantic-errors -O3) I get strict aliasing warning.
But I'm not saying that there is something wrong with libev and that
those warnings should be fixed asap (surprise-surprise).
I'm just curious why libev needs all those casts that produce that
warning in a first place. For example, why not to have it that way:
#define ev_init(ev,cb_) do { \
- ((ev_watcher *)(void *)(ev))->active = \
- ((ev_watcher *)(void *)(ev))->pending = 0; \
+ (ev)->active = \
+ (ev)->pending = 0; \
ev_set_priority ((ev), 0); \
ev_set_cb ((ev), cb_); \
ev_set_cb ((ev), cb_); \
} while (0)
Since ev must be a watcher, it will have "active" and "pending"
members and two-steps cast is not really necessary. Another example:
-# define ev_set_cb(ev,cb_) (ev_cb_ (ev) = (cb_), memmove (&
((ev_watcher *)(ev))->cb, &ev_cb_ (ev),
sizeof (ev_cb_ (ev))))
+# define ev_set_cb(ev,cb_) (ev)->cb = (cb_)
Why to use memmove when "ev->cb" and "cb_" must have the same type and
are simply assignable? Curiously enough, I noticed that those
memmove's were added exactly to "fix a potential aliasing issue".
I'm sure all those things are done for a reason, and I'm wondering
what those reasons are. Maybe somebody could write a few lines
explaining why libev needs those casts and memmove's?
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