Issue #16352 has been updated by marcandre (Marc-Andre Lafortune).


Couldn't we dedicate a special "size" value to indicate "extended marshal size" (say `SIZEOF_LONG - 1`), such that compatibility with all current and future marshal dumps is maintained, with the exception of a marshal object that would actually happen to have exactly a size of `SIZEOF_LONG - 1`?

```
def marshal_dump
  if size < SIZEOF_LONG - 1
    # business as usual, proceed with old dump
  else
    io << SIZEOF_LONG - 1 << size_as_int_64 << # presumable rest of output similar...
  end
end

def marshal_load
  io >> size
  if size == SIZEOF_LONG - 1
    # Assume new format
    io = io.read_int_64
    # ...
  else
    # ... as before
  end
end
```

----------------------------------------
Feature #16352: Modify Marshal to dump objects larger than 2 GiB
https://bugs.ruby-lang.org/issues/16352#change-85980

* Author: seoanezonjic (Pedro Seoane)
* Status: Open
* Priority: Normal
----------------------------------------
Using a gem called Numo-array to handle matrix operations, I found the following error while saving a large matrix:

```
in `dump': long too big to dump (TypeError)
```

Github thread is https://github.com/ruby-numo/numo-narray/issues/144. Digging with the authors, I found the following code that reproduces the error:

```
ruby -e 'Marshal.dump(" "*2**31)'
```

Executed in:
ruby 2.7.0dev (2019-11-12T12:03:22Z master 3816622fbe) [x86_64-linux]

The marshal library has a limit based on constant `SIZEOF_LONG`. This check is performed in [here](https://github.com/ruby/ruby/blob/e7ea6e078fecb70fbc91b04878b69f696749afac/marshal.c#L301L321). I don't understand the motivation of this limit. It has a great impact on libraries that need to serialize large objects such as numeric matrix. In this case, the limit >= 2 GiB is reached easily, and it blocks ruby development. I found another related bug report: #1560, but the Marshal problem was not addressed in it.



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