`virtual`

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ethdebug/format/pointer/region/virtual
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "schema:ethdebug/format/pointer/region/virtual"

title: ethdebug/format/pointer/region/virtual
description: |
  A schema for representing a region of data that is not stored in any EVM
  data location, but is computed from the machine state: the bytes of an
  expression's value.

  A compiler may use a virtual region for a value that has no place in the
  machine state of its own, e.g., a variable the optimizer removed whose
  value can still be computed from other values that remain.

  This schema is constructed by extending the base region schema
  and the schema for the fragment addressing scheme.
type: object
allOf:
  - title: '{ "location": "virtual" }' # note: whitespace chars are \255 (nbsp)
    properties:
      location:
        const: virtual

    required:
      - location
  - $ref: "schema:ethdebug/format/pointer/region/base"
  - $ref: "schema:ethdebug/format/pointer/scheme/fragment"

unevaluatedProperties: false

examples:
  # `x = a + 1` after the optimizer removed `x`, where a region named `a`
  # comes before this one
  - name: x
    location: virtual
    expression:
      ~wordsized:
        ~sum:
          - ~read: a
          - 1
  # the first 4 bytes of a hash
  - name: tag
    location: virtual
    expression:
      ~keccak256:
        - ~read: a
    length: 4

ethdebug/format/pointer/region/virtual
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "schema:ethdebug/format/pointer/region/virtual",
  "title": "ethdebug/format/pointer/region/virtual",
  "description": "A schema for representing a region of data that is not stored in any EVM\ndata location, but is computed from the machine state: the bytes of an\nexpression's value.\n\nA compiler may use a virtual region for a value that has no place in the\nmachine state of its own, e.g., a variable the optimizer removed whose\nvalue can still be computed from other values that remain.\n\nThis schema is constructed by extending the base region schema\nand the schema for the fragment addressing scheme.\n",
  "type": "object",
  "allOf": [
    {
      "title": "{ \"location\": \"virtual\" }",
      "properties": {
        "location": {
          "const": "virtual"
        }
      },
      "required": [
        "location"
      ]
    },
    {
      "$ref": "schema:ethdebug/format/pointer/region/base"
    },
    {
      "$ref": "schema:ethdebug/format/pointer/scheme/fragment"
    }
  ],
  "unevaluatedProperties": false,
  "examples": [
    {
      "name": "x",
      "location": "virtual",
      "expression": {
        "~wordsized": {
          "~sum": [
            {
              "~read": "a"
            },
            1
          ]
        }
      }
    },
    {
      "name": "tag",
      "location": "virtual",
      "expression": {
        "~keccak256": [
          {
            "~read": "a"
          }
        ]
      },
      "length": 4
    }
  ]
}