digitalmars.D.learn - Problems with std.experimental.allocator
I realize these are not yet stable but I would like to know if I
am doing something wrong or is it a lib bug.
My first attempt was to do this:
theAllocator = allocatorObject(Region!MmapAllocator(1024*MB));
If I got it right this doesn't work because it actually does this:
1. Create Region struct and allocate 1024MB from MMapAllocator
2. Wrap the struct in IAllocator by copying it because it has
state
3. Destroy original struct which frees the memory
4. Now the struct copy points to released memory
Am I right here?
Next attempt was this:
theAllocator =
allocatorObject(Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB)));
Since I give actual memory instead of the allocator to the Region
it can not dealocate that memory so even the copy will still
point to valid memory. After looking at what will the
allocatorObject do in this case my conclusion is that it will
take a "copyable" static if branch and create an instance of
CAllocatorImpl which will have a "Region!() impl" field within
itself but given Region!() struct is never copied into that field.
Am I right here?
If I am right about both are then these considered as lib bugs?
I finally got it working with:
auto newAlloc =
Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB));
theAllocator = allocatorObject(&newAlloc);
Next I tried setting processAllocator instead of theAllocator by
using:
auto newAlloc =
Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB));
processAllocator = sharedAllocatorObject(&newAlloc);
but that complained how it "cannot implicitly convert expression
`pa` of type `Region!()*` to `shared(Region!()*)`" and since
Region doesn't define its methods as shared does this mean one
can not use Region as processAllocator? If that is so, what is
the reason behind it?
Sep 02 2017
Igor <stojkovic.igor gmail.com>
On Saturday, 2 September 2017 at 11:23:00 UTC, Igor wrote:
I realize these are not yet stable but I would like to know if
I am doing something wrong or is it a lib bug.
My first attempt was to do this:
theAllocator = allocatorObject(Region!MmapAllocator(1024*MB));
If I got it right this doesn't work because it actually does
this:
1. Create Region struct and allocate 1024MB from MMapAllocator
2. Wrap the struct in IAllocator by copying it because it has
state
3. Destroy original struct which frees the memory
4. Now the struct copy points to released memory
Am I right here?
Next attempt was this:
theAllocator =
allocatorObject(Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB)));
Since I give actual memory instead of the allocator to the
Region it can not dealocate that memory so even the copy will
still point to valid memory. After looking at what will the
allocatorObject do in this case my conclusion is that it will
take a "copyable" static if branch and create an instance of
CAllocatorImpl which will have a "Region!() impl" field within
itself but given Region!() struct is never copied into that
field.
Am I right here?
If I am right about both are then these considered as lib bugs?
I finally got it working with:
auto newAlloc =
Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB));
theAllocator = allocatorObject(&newAlloc);
Next I tried setting processAllocator instead of theAllocator
by using:
auto newAlloc =
Region!()(cast(ubyte[])MmapAllocator.instance.allocate(1024*MB));
processAllocator = sharedAllocatorObject(&newAlloc);
but that complained how it "cannot implicitly convert
expression `pa` of type `Region!()*` to `shared(Region!()*)`"
and since Region doesn't define its methods as shared does this
mean one can not use Region as processAllocator? If that is so,
what is the reason behind it?
After a lot of reading I learned that I need a separate
implementation like SharedRegion and I tried implementing one. If
anyone is interested you can take a look here
https://github.com/igor84/dngin/blob/master/source/util/allocators.d. It
doesn't have expand at the moment but I tried making it work with this:
processAllocator = sharedAllocatorObject(shared
SharedRegion!MmapAllocator(1024*MB));
I did it by reserving first two bytes of allocated memory for
counting the references to that memory and then increasing that
count on postblit and decreasing it in destructor and identity
assignment operator. I then only release the memory if this count
gets bellow 0. Problem is I couldn't get it to compile since I
would get this error on above line:
Error: shared method
util.allocators.SharedRegion!(MmapAllocator, 8u,
cast(Flag)false).SharedRegion.~this is not callable using a
non-shared object
I couldn't figure out why is it looking for non-shared
destructor. If I remove shared from destructor then I get that
"non-shared method SharedRegion.~this is not callable using a
shared object" in std/experimental/allocator/package.d(2067).
I currently use it with pointer construction:
https://github.com/igor84/dngin/blob/master/source/winmain.d#L175
Sep 03 2017