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WebAssembly · 03 Compile and Instance
Series contents · Technology map
Stage: Modules and Numeric Contracts · External example · preview instructions · Storage ID: webassembly-step-03
Goals and learning outcomes
- Learning outcome: explain the role of Module. Input cases: the same module and different first elements.
- Deliverable: the first element value for each instance. Explain the rationale for handling Instance, linking it to the code.
Prerequisites
Prepare the experiment results for Text format and Build from Unit 2, “WAT and Binary”.
Key concepts and explanations
Module
The result of compile is compiled code. Distinguish it from an instance with execution state.
Instance
Multiple instances can be created from the same module. Whether their memories are shared depends on the definitions.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. The iframe preview is an experiment with WebAssembly.Memory and JS reference computations; do not present it as execution of an actual Wasm module. Practice with actual modules in a separate Node 22+ environment or a controlled local web project. Use kernel.wat·kernel.wasm·benchmark.mjs in the existing src/labs/webassembly-02·03 folders, and rebuild with the official wat2wasm tool when modifying WAT. Preserve CSP·isolation, and record measurements yourself.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In day-3.mjs in a separate practice project, create two instances after WebAssembly.compile and modify each memory. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: the same module and different first elements. Baseline: one. Run under the baseline conditions, then record observations and errors in notes/day-3.md.
- Variable: instances; changed value: two. Run again through the same input path. Deliverable to save: the first element value for each instance. Hypothesis to check: Internally defined memory remains independent in each instance. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| instances | one | two | Internally defined memory remains independent in each instance. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: the first element value for each instance. Results are available for both the baseline and changed conditions, allowing comparison of 2 conditions; input values and the execution environment are recorded together.
- The explanation of differences between the two conditions connects both concepts: Module and Instance. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Module affect in this exercise? Input cases: the same module and different first elements.
- Variable: instances. Hypothesis to check: Internally defined memory remains independent in each instance. Did the actual results agree with the hypothesis? Explain the evidence in terms of Instance.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
Standalone WAT + Node assertions; iframe CSP blocks Wasm compilation.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.