docs: session handoff document for session 9

session-ses_128f.md

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+# Session Handoff: WiseCode Visual C IDE — Session 9
+
+**Date:** June 23, 2026
+
+## Summary
+
+Refactored code generation to eliminate duplicated logic, added loop support via goto labels, fixed C code quality issues, and added compilation tests.
+
+---
+
+## Changes
+
+### Shared codegen module (`codegen/index.js` — new)
+Pure C code generation with zero DOM dependencies. Exports as `window.CodeGen` (browser) and `module.exports` (Node.js):
+- `branchDescendants(roots, isDecision)` — discovers reachable blocks, excluding decisions
+- `emitBranch(roots, stop, visited, isDecision)` — emits C code for a branch via `generateCode`, with `goto` on back-edges
+- `generateCallWithError(ifHeader, errTargets, okTargets, isDecision)` — shared visited set across all branches to prevent duplicate labels
+- `generateCFile(entryBlock, includes, declarations)` — assembles complete C file
+
+### Browser blocks adapted
+- **`blocks-proc.js`**: `_branchDescendants` and `_emitBranch` are now 3-line adapters passing `b instanceof WCDecision` to `CodeGen`. `_generateCallWithError` delegates to `CodeGen.generateCallWithError`.
+- **`blocks-algo.js`**: `WCDecision._emitBranch` delegates to `generateCode` (not `generateOwnCode`), uses `visited` in-place. `_emitBranch` skips roots already visited by prior roots.
+- **`index.html`**: `codegen/index.js` loaded before `blocks-proc.js`.
+
+### Loop support
+Every block in `#draw-area` emits a C label (`block_id:`) before its code. `generateNextCode` emits `goto label;` when a target is already visited (back-edge). `_emitBranch` emits `goto label;` when encountering a visited block.
+
+Files changed: `wcblock.js`, `blocks-algo.js`, `blocks-proc.js`, `codegen/index.js`
+
+### C code quality fixes
+- **Double `return 0`**: `wcprogram.js` now checks if the body already contains a return/exit before appending the hardcoded `return 0;\n`.
+- **Variable labels**: `WCBlock.generateCode` checks `_isFlowBlock` (set from `#draw-area` presence). Variable blocks in `#variable-area` skip label/goto logic.
+- **Default array removed**: Unconditional `vertices` array creation in `app.js:main()` removed. Templates should create their own variables.
+
+### Compilation tests (`tests/compile/`)
+- **Makefile**: Uses `pkg-config`, compiles with `-Wall -Wextra -fsyntax-only`
+- **run.js**: Uses shared `CodeGen` module — no duplicated `branchDescendants`/`emitBranch`/`generateCode` logic
+- 5 test cases (console, error-simple, error-merge, error-sequential, error-value) all pass
+
+### WCEnd modal bugfix
+- Colour: `dataset.exitError` instead of `tagName === "WC-END"` — success ENDs default to blue
+- Value: `setAttribute("value", ...)` alongside `input.value = ...` — `cloneNode(true)` preserves formatted display
+- 4 regression tests added
+
+### Warning icon overlap
+`padding-right` added to `.proccall-header` and `.end-header` when warnings active, preventing `::after` text from colliding with the `.block-warn` icon.
+
+### Template spacing
+Block gap increased from 16px to 40px. Error WCEnd blocks added to console and SDL3 templates with error-hook connections.
+
+---
+
+## Commit log
+
+```
+e879e21 fix: variable blocks no longer emit labels; remove default array variable
+7451def fix: double return 0 in generated C output
+439cc6e feat: loop support via goto labels on each block
+f1eed2d refactor: extract pure codegen into shared module, remove duplication
+9dd79c2 chore: remove stale test-compile.js
+8522ece test: C compilation tests for generated template code
+3657a22 fix: WCEnd editor modal pre-loads correct colour and errno value
+68da559 refactor: unwrap nested if-else in error-path code generation
+5caa306 fix: prevent deletion of library procedures
+```
+
+## File inventory (key files)
+
+| File | Lines | Notes |
+|------|-------|-------|
+| `codegen/index.js` | ~150 | Pure codegen module, shared browser+Node |
+| `blocks-proc.js` | ~600 | ProcCall with codegen delegation |
+| `blocks-algo.js` | ~560 | Decision/End blocks with label support |
+| `wcblock.js` | ~330 | Base class with _isFlowBlock, label/goto |
+| `wcprogram.js` | ~300 | Double-return guard |
+| `tests/compile/run.js` | ~230 | Compilation tests using CodeGen module |
+| `tests/compile/Makefile` | ~40 | pkg-config based build |
+| `tests/app/test-runner.js` | ~845 | Browser tests |
+| `shell.nix` | ~56 | Added gcc, mesa |
+| `style.css` | ~1340 | Warning icon padding fix |