On Thursday, 13 March 2014 at 19:28:59 UTC, Walter Bright wrote:
On 3/13/2014 1:43 AM, Don wrote:
The worst breaking change in D2, by far, is the prevention of
array stomping.
After that change, our code still runs, and produces exactly
the same results,
but it is so slow that it's completely unusable. This one of
the main reasons
we're still using D1.
I didn't know this. I'd like more details - perhaps I can help
with how to deal with it.
Our entire codebase assumes that stomping will happen. Simplest
example:
T[] dupArray(T)(ref T[] dest, T[] src)
{
dest.length = src.length;
if (src.length) {
dest[] = src[];
}
return dest;
}
This is equivalent to dest = src.dup, but if dest was already
long enough to contain src, no allocation occurs.
Sure, we can add a call to "assumeSafeAppend()" everywhere. And I
mean *everywhere*. Every single instance of array creation or
concatentation, without exception. Almost every array in our
codebase is affected by this.
