---
title: "wasi-memory — Mova code model"
description: "Mova code model of wasi-host/src/lib.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/wasi-host/src/lib.rs.groupant/wasi-memory.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

This page as HTML: <https://groupants.elamur.ai/free/en/mova/wasi-host/src/lib.rs.groupant/wasi-memory.groupant/>

# wasi-memory

The groupant beside wasi-host/src/lib.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant_fragment
- **status:** partial source bound model
- **source:** [`wasi-host/src/lib.rs`](https://github.com/ElamurAI/mova-free/blob/main/wasi-host/src/lib.rs)
- **source SHA-256:** `91213ce903810791…`
- **covers:** range accepts [ptr,ptr+len) only with checked end<=memory length. off checks u32 overflow. iovs rejects n>1024 before coordinates, then reads n pairs of LE u32; get_str validates UTF8 after copying. filestat emits64 bytes with fixed offsets. (bytes 2819–4771)
- **part of:** [wasi-runtime](https://md.groupants.elamur.ai/free/en/mova/wasi-host/src/lib.rs.groupant/)
- **repository folder:** [`wasi-host/src/lib.rs.groupant/wasi-memory.groupant`](https://github.com/ElamurAI/mova-free/tree/main/wasi-host/src/lib.rs.groupant/wasi-memory.groupant)
- **repository commit:** `48f2e6f74146`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial | [approximant](#approximant) |
| **ast** | partial | `../syntax.json` |
| **cost** | symbolic source derived | [invariant](#invariant) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [invariant](#invariant) |
| **tests** | executed bounded checks | [tests](#tests) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `behavior_complement` | behavior_complement | partial source derived model | [behavior_complement](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `zero_coordinates` | zero_coordinates | partial source derived model | [zero_coordinates](#zero-coordinates) |
| `fault_precedence` | fault_precedence | partial source derived model | [fault_precedence](#fault-precedence) |
| `byte_layout` | byte_layout | partial source derived model | [byte_layout](#byte-layout) |
| `integer_boundary` | integer_boundary | partial source derived model | [integer_boundary](#integer-boundary) |

## Model text


### descriptant

#### wasi-memory

range accepts [ptr,ptr+len) only with checked end<=memory length. off checks u32 overflow. iovs rejects n>1024 before coordinates, then reads n pairs of LE u32; get_str validates UTF8 after copying. filestat emits64 bytes with fixed offsets.

##### Epoch 2026-10-31

Prospective review recorded before edits. Source review found late output FAULT effects and weaker-than-capability rights metadata; these are modeled as current behavior rather than silently repaired. Only bounded new test blocks were added; production code remains unchanged. Actual finite results and exact restoration receipts live under $MOVA_DATA/runs/octopus-wave31-wasi-2026-10-31. No full mlab guest, frozen suite, GPU or corpus run. This node retains its scoped observations for future refinement.

### approximant

#### Forward relation

range accepts [ptr,ptr+len) only with checked end<=memory length. off checks u32 overflow. iovs rejects n>1024 before coordinates, then reads n pairs of LE u32; get_str validates UTF8 after copying. filestat emits64 bytes with fixed offsets.

Scope: `wasi-memory`. State and transitions follow the authoritative source, including partial effects before errors. No executable approximate replacement is attached: categorical errno/effects and module execution lack a useful validated percentage metric; future numerical profiles may only use1/2/5/10% caps after domain/reference evidence.

### invariant

#### Invariant and cost

range accepts [ptr,ptr+len) only with checked end<=memory length. off checks u32 overflow. iovs rejects n>1024 before coordinates, then reads n pairs of LE u32; get_str validates UTF8 after copying. filestat emits64 bytes with fixed offsets.

The invariant is conditional on the admitted transition: Successful range excludes end>memory length; decoded LE scalar excludes different values for identical selected bytes. n>1024 excludes successful iovec decode irrespective of ptr.

Cost: O(n) iovec table and allocation, O(bytes) string/copy; scalar accesses O(1).

No wall-time gain, universal resource bound or atomic rollback is inferred. External Vfs/wasmi/native-mlab work remains separately charged.

### models

## Typed model catalog

### behavior_complement

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: Successful range excludes end>memory length; decoded LE scalar excludes different values for identical selected bytes. n>1024 excludes successful iovec decode irrespective of ptr.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.

### reverse_reconstruction

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: Successful scalar loads recover the selected bytes uniquely, but all other bytes and original provenance remain arbitrary. A FAULT permits many bad coordinates; ILSEQ implies an in-range invalid UTF8 slice.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.

### zero_coordinates

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: range(len,0) succeeds while range(len+1,0) faults; zero iovs reads no table bytes.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.

### fault_precedence

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: n>1024 yields INVAL even when ptr=u32::MAX; malformed table coordinates yield FAULT before file lookup.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.

### byte_layout

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: filestat dev zero, ino at8, type16, nlink24=1, size32, atim40=mtime, mtim48, ctim56.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.

### integer_boundary

Subject: `wasi-host/src/lib.rs` at SHA-256 `91213ce9038107912c2dd707c3a6639a2d723cdfceb02981a166a6853800248e`, scope `wasi-memory`. Domain: the source transition and bounded fixtures described in approximant.md; readable valid host resources where required. Observation: returned values, byte coordinates, state/effect order, not total-system semantics. Operator/relation: off(u32::MAX,1) faults; range uses usize checked addition; put casts slice length to u32, so giant host slices are outside tested domain.

Status: partial source-derived relation; complement is a scoped exclusion hypothesis, reverse preserves all compatible antecedents described rather than a chosen inverse. Assumptions: production branch order, declared coordinate/resource premises; no completeness claim for untested inputs. Evidence: tests.md distinguishes actual execution from source review; finite observations can falsify but not prove the relation.


### tests

#### Checks and limits

Named actual-source tests run twice per debug/release; exact commands and numeric statuses retained externally. Test success is finite evidence only.

Exact names: tests::args_and_prestat, tests::wave31_memory_poll_and_descriptor_boundaries.

Memory tests bypass linker ABI; tiny empty/unreachable guests exercise engine outcomes only. The CLI test uses isolated import/export/journal fixtures.

Five compiled production/helper-source controls: append offset, virtual clock advance, trap status, CLI export gate and newest-mtime max. Each compiles, fails its selected assertion, restores exact original bytes and passes again. These controls cover their target relations, not every node. No assertion-only mutants. See external source-test-map.json, native-commands.json, verify.rs and numeric/raw receipts in $MOVA_DATA/runs/octopus-wave31-wasi-2026-10-31. The example main and frozen mlab paths are never executed.