Re: Custom Storage Pool questions

[Egil H H <ehh.public@gmail.com>]

On Tuesday, September 14, 2021 at 2:48:16 AM UTC+2, Jere wrote:
> 
> Yes, but if you look at that blog, they are allocating space for the /user/ data 
> and for the Next/Prev for controlled types and First/Last for unconstrained 
> arrays in addition to the size specified by allocate. 
> 

Yes, but if you look at that blog, they explain the default layout of fat pointers, 
and the special value that need to be set on access types for the layout to 
change. If you use such a GNAT-ism, your storage pool will also be bound
to GNAT...


ie: 
"GNAT typically uses a "fat pointer" for this purpose: the access itself is in fact
a record of two pointers, one of which points to the bounds, the other points to
the data. This representation is not appropriate in the case of the header 
storage pool, so we need to change the memory layout here."

and:
"we need to ensure that the bounds for unconstrained arrays are stored next to 
the element, not in a separate memory block, to improve performance. This is 
done by setting the Size attribute on the type. When we set this size to that of 
a standard pointer, GNAT automatically changes the layout,"


-- 
~egilhh