Redesign VM output management

[chfast]

I would like to propose change in the VM-related API. Now the user have to provide the output buffer where the VM will copy the output (it comes from current CALL semantics).
I want to change that to return the output buffer reference with attached virtual destructor to the user. The user is responsible to copy whatever it wants and release the buffer.

This should be aligned with:

1. The way how CREATE works.
2. EIP 5: Gas costs for return values EIPs#8.
3. Changes planned in EVM-C: aligning external and internal calls.

[chfast]

@chriseth @gcolvin can you review this? Details will come with a PR.

[gcolvin]

Can't get to Github for some reason.  Will review tomorrow or
  Saturday.  Thanks.


On 9/28/16 7:36 PM, Paweł Bylica wrote:


  @chriseth @gcolvin
    can you review this? Details will come with a PR.
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[chriseth]

Sounds good! The question would be: How much will be retained? The full memory of the callee or will the return part be copied somewhere else in between? I think it should be quite safe to retain the full memory because it will be deleted in the next step.

[chfast]

Exactly. You return full memory and the reference to the output buffer
within this memory. The user frees the memory as soon as it does not need
the output any more.

On Wed, Oct 5, 2016, 00:37 chriseth [email protected] wrote:

Sounds good! The question would be: How much will be retained? The full
memory of the callee or will the return part be copied somewhere else in
between? I think it should be quite safe to retain the full memory because
it will be deleted in the next step.

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