On Thursday, 12 May 2016 at 09:25:49 UTC, Stefan Koch wrote:
On Thursday, 12 May 2016 at 08:41:25 UTC, John Burton wrote:
I've been unable to find a clear definitive answer to this so
please point me to one if it already exists in the manual or
the forums.
Is it safe to cast pointer types?
double data;
long p = *cast(long*)&data;
(Excuse any silly syntax errors as I'm doing this on my phone).
This used to be possible in C until people recently decided it
not only was wrong, it had always been wrong :P (Ok I'm not
entirely serious there but that's what this issue feels
like...)
Is this legal / valid in D and if not what is the appropriate
way to efficiently access data like this?
How would such a cast be safe?
"Safe" as in it produces a valid long value by interpreting the
bytes of the stored double. Obviously if it works it's very
system dependent.
But in C it's simply undefined behavior to read a value stored
using one pointer type using a pointer to a different type. (With
some additional rules about char in a few cases).
The whole strict aliasing businesss
