Implement a Wasm Stack Machine Interpreter for a Subset of Instructions

Wasm Stack Machine Interpreter

Wasm execution is specification-defined stack semantics. Your interpreter maintains an operand stack, locals array, and structured control frames for blocks and branches.

Instruction Subset

Core patterns:

• \`local.get\` / \`local.set\`: locals indexed 0..n
• \`i32.const\`, \`i32.add\`, \`i32.sub\`: integer stack ops
• \`br\`, \`br_if\`: branch with label depth
• \`call\`, \`return\`: functions and exits

Validation (next task) proves stack depth correct before you run. Execution pops operands, pushes results, and updates \`pc\` through the current function body.

For example, \`(param i32 i32) (result i32)\` with body \`local.get 0; local.get 1; i32.add\` leaves one \`i32\` on the stack.

\`\`\` stack: [] -> [a] -> [a,b] -> [a+b] \`\`\`

Design Notes

Structured control (`block`, `loop`, `if`) requires a control stack in addition to the operand stack. Branch depths index into that stack; getting depth wrong traps at runtime even after validation passes.

For This Exercise

This exercise asks you to implement a Wasm interpreter for a curated opcode subset. You will execute validated function bodies with an explicit operand stack matching the spec's stack effects.

You will use the same mental model here when reading production interpreter source later in the track. Sketch one concrete input on paper, predict the outcome, then confirm with code. That discipline catches logic errors early and makes debugging far faster when you extend the implementation in follow-on tasks.