On Sat, 15 Feb 2014, Jürgen Hestermann wrote:
Am 2014-02-10 09:13, schrieb Michael Van Canneyt:
No. There is no COW, only ref. counting. SetLength just forces an unique
instance of the array if needed.
The documentation explicitly mentions that:
'Dynamic arrays are reference counted: assignment of one dynamic array-type
variable to another will let both variables point to the same array.
Contrary to ansistrings, an assignment to an element of one array will
be reflected in the other: there is no copy-on-write.'
But what do these sentences say?
They say that there is *no* copy-on-write.
Correct.
So why does it suddenly do copy-on-write when using SetLength?
Copy-On-Write means that if you write to *an element* of the array,
the array is duplicated if it has a ref count>0. As with strings.
Since this does not happen for dynamic arrays, there is no copy on write.
That setlength behaves rather freakish for dynamic arrays, does not
mean we have copy-on-write.
Michael.
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