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Add IS_STATIC opcode #2975

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Sep 13, 2020
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Add IS_STATIC opcode #2975

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39 changes: 39 additions & 0 deletions EIPS/eip-2970.md
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---
eip: 2970
title: IS_STATIC opcode
author: Vitalik Buterin (@vbuterin)
discussions-to: https://ethereum-magicians.org/t/is-static-opcode-useful-for-aa/4609
status: Draft
type: Standards Track
category: Core
created: 2020-09-13
---

## Simple Summary

Add a `IS_STATIC (0x4A)` opcode that pushes `1` if the current context is static (ie. the execution is in a `STATICCALL` or a descendant thereof, so state-changing operations are not possible), and `0` if it is not.

## Abstract
Comment on lines +12 to +16
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Suggested change
## Simple Summary
Add a `IS_STATIC (0x4A)` opcode that pushes `1` if the current context is static (ie. the execution is in a `STATICCALL` or a descendant thereof, so state-changing operations are not possible), and `0` if it is not.
## Abstract
## Simple Summary
Adds an opcode to detect if the current call context is limited to read-only operations.
## Abstract
Add a `IS_STATIC (0x4A)` opcode that pushes `1` if the current context is static (ie. the execution is in a `STATICCALL` or a descendant thereof, so state-changing operations are not possible), and `0` if it is not.

The current simple summary feels more like an abstract due to the level of detail it goes into and how it basically mirrors the specification.

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It simply does not make sense to have both.

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@MicahZoltu MicahZoltu Sep 23, 2020 •
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The purpose of the simple summary is to give a one sentence overview of what this EIP is. You can imagine it showing up in some places as a sub-title or inline description. Think "email subject line". Abstract's purpose is to describe the specification in human readable terms, with perhaps some of the minor details and edge cases left out.

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Great explanation, thank.


## Motivation

The main intended use case is to allow account abstraction (EIP 2938) to be extended so that accounts can allow static calls from the outside (which are harmless to AA's security model) but not state-changing calls.

## Specification

Add a `IS_STATIC (0x4A)` opcode that pushes `1` if the current context is static (ie. the execution is in a `STATICCALL` or a descendant thereof, so state-changing operations are not possible), and `0` if it is not.

## Rationale

Determining staticness is already possibly using the following hacky technique: make a `CALL` with limited gas, and inside that `CALL` issue one `LOG` and exit. If the context is static, the `CALL` would fail and leave a 0 on the stack; if the context is non-static, the `CALL` would succeed. However, this technique is fragile against changes to gas costs, and is needlessly wasteful. Hence, the status quo neither allows a reasonably effective way of determining whether or not the context is static, nor provides any kind of invariant that executions that do not fail outright will execute the same way in a static and non-static context. This EIP provides a cleaner way of determining staticness.

## Backwards Compatibility

TBD

## Security Considerations

TBD

## Copyright
Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).