[MLton] Crash fread(...) failed (only read 0) (Cannot allocate memory) during deepFlatten with MLton 20070826

[Matthew Fluet]

On Tue, 22 Apr 2008, Nicolas Bertolotti wrote:
> There was actually another bug in heap.c. Here is an additional patch to fix it:
> --- mlton/runtime/gc/heap.c   2008-04-11 19:12:58.000000000 +0200
> +++ mltonp1/runtime/gc/heap.c 2008-04-22 16:24:50.000000000 +0200
> @@ -337,6 +337,7 @@
>       }
>       GC_diskBack_read (data, curHeapp->start, size);
>       GC_diskBack_close (data);
> +      curHeapp->oldGenSize = size;
>     } else {
>       GC_diskBack_close (data);
>       if (s->controls.messages)

Yes, I was just coming to that exact conclusion.

> Unfortunately, now, I get the following error:
>            deepFlatten starting
> Out of memory.  Unable to allocate 1,686,393,408 bytes.
>
> ... which, I guess, is a different problem.

It is a different problem, in the sense that you succeeded (at least 
once) in writing the heap to disk, allocating a larger heap, and reading 
the heap from disk.  Getting an out of memory error suggests that even 
after writing the heap to disk and releasing it, the operating system was 
unable to mmap 1.6G.  That seems strange, even on a 32bit system, where 
the virtual address space is 4G, though I suppose it could happen with 
sufficient fragmentation.

If you compile with @MLton gc-messages --, you should get a more detailed 
memory listing of what memory is reserved, which might indicate whether 
there is some extra memory being held.