On Tuesday, 30 September 2014 at 14:01:17 UTC, Steven
Schveighoffer wrote:
Assertion passes with D1/Tango runtime but fails with current
D2
runtime. This happens because `result.ptr` is not actually a
pointer
returned by gc_qalloc from array reallocation, but interior
pointer 16
bytes from the start of that block. Druntime stores some
metadata
(length/capacity I presume) in the very beginning.
This is accurate, it stores the "used" size of the array. But
it's only the case for arrays, not general GC.malloc blocks.
Alternative is to use result.capacity, which essentially looks
up the same thing (and should be more accurate). But it doesn't
cover the same inputs.
Why is it stored in the beginning and not in the end of the block
(like capacity)? I'd like to explore options of removing interior
pointer completely before proceeding with adding more special
cases to GC functions.
