Please consider the following program:

import std.experimental.allocator.mallocator;
import std.experimental.allocator.building_blocks.allocator_list : AllocatorList;
import std.experimental.allocator.building_blocks.free_list;
import std.experimental.allocator;
import std.stdio;

enum uint size = 1104;

alias ScalableFreeList = AllocatorList!((n) =>
    ContiguousFreeList!(Mallocator, 0, unbounded)(size * 128, size)
);

void main(string[] args)
{
  void[][20] allocs;
  ScalableFreeList allocator;

  for(int i=0; i < 100; i++)
  {
    writefln("pass %d", i);
    foreach(ref alloc; allocs)
    {
      alloc = allocator.allocate(size);
      writefln("%x", alloc.ptr);
    }

    foreach(alloc; allocs)
    {
      allocator.deallocate(alloc);
    }
  }
}


I would assume that this program should run forever and never run out of memory. But instead it triggers an assert inside alocator_list in pass 11. So I assume this is some bug in std.allocator?

Also whats interresting. The first allocation in each new pass is _not_ the last allocation to be freed. Instead it seems to "leak" one allocation each pass.

From the output of the program:

229a290fd60 <- same
229a2932570 <- leaked?
pass 11
229a290fd60 <- same

Or can anyone see a bug in my program?

Kind Regards
Benjamin Thaut

On 10/25/2016 11:30 AM, Benjamin Thaut wrote:
> Please consider the following program:
[...]
> I would assume that this program should run forever and never run out of
> memory. But instead it triggers an assert inside alocator_list in pass
> 11. So I assume this is some bug in std.allocator?

I can confirm the crash with 2.071.2. But it doesn't happen with 2.072.0-b2. So, bug that has already been fixed?

> Also whats interresting. The first allocation in each new pass is _not_
> the last allocation to be freed. Instead it seems to "leak" one
> allocation each pass.
>
> From the output of the program:
>
> 229a290fd60 <- same
> 229a2932570 <- leaked?
> pass 11
> 229a290fd60 <- same

Also looks ok with 2.072.0-b2:

7f448c7ccdb0
7f448c7cd200
pass 99
7f448c7cd200
7f448c7ccdb0