138 lines
4.7 KiB
Bash
Executable File
138 lines
4.7 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Post-process Emscripten output for Node.js 22+ ES module compatibility.
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#
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# Emscripten (3.1.x) produces ES module output that still references
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# `require()`, `__dirname`, and `__filename` — all of which are undefined
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# in pure ESM. This script patches magic.js to:
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# 1. Alias every `require("x")` call to `___cr("x")` (createRequire).
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# 2. Inject ESM-safe `__filename` / `__dirname` / `require` at module top.
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# 3. Sync `___emscripten_embedded_file_data` from the .wasm global.
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#
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# Usage: post-build.sh <magic.js> <magic.wasm>
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#
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# Idempotent — safe to run multiple times.
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#
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# WARNING: These patches depend on exact text patterns emitted by a specific
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# Emscripten version. If you upgrade emsdk, verify the patches still apply
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# (see .github/workflows/main.yml for the pinned version).
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set -euo pipefail
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if [ $# -ne 2 ]; then
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echo "Usage: $0 <magic.js> <magic.wasm>" >&2
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exit 1
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fi
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JS=$1
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WASM=$2
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if [ ! -f "$JS" ] || [ ! -f "$WASM" ]; then
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echo "Error: $JS or $WASM not found." >&2
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exit 1
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fi
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# Portable in-place sed: BSD (macOS) and GNU diverge on -i.
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# Using a temp file + mv keeps both happy without relying on -i at all.
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_sed_inplace() {
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local expr=$1 file=$2
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local tmp
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tmp=$(mktemp)
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sed "$expr" "$file" > "$tmp"
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mv "$tmp" "$file"
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}
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# --- 1 & 2. ES module compatibility -----------------------------------------
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if ! grep -q 'createRequire' "$JS"; then
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echo "[post-build] Injecting ESM createRequire + __filename/__dirname shims"
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_sed_inplace 's/require("\([^"]*\)")/___cr("\1")/g' "$JS"
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_sed_inplace '1s|^|\nimport{createRequire as ___cr}from"module";\nimport{fileURLToPath as ___fup}from"url";\nimport{dirname as ___dn}from"path";\nvar __filename=___fup(import.meta.url);\nvar __dirname=___dn(__filename);\n|' "$JS"
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fi
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# Ensure a top-level `require` binding exists (Emscripten's environment probe
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# does `typeof require == "function"`, which would otherwise be "undefined").
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# Skip if Emscripten already emits one (newer versions do).
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if ! grep -qE 'var[[:space:]]+require[[:space:]]*=' "$JS" \
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&& grep -q 'import{createRequire as ___cr}from"module";' "$JS"; then
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echo "[post-build] Adding top-level require binding"
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_sed_inplace 's|import{createRequire as ___cr}from"module";|import{createRequire as ___cr}from"module";var require=___cr(import.meta.url);|' "$JS"
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fi
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# --- 3. Sync ___emscripten_embedded_file_data from .wasm --------------------
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# Emscripten sometimes bakes a stale constant into magic.js after an
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# incremental rebuild. Read the true value from the WASM global section
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# (section id 6, global index 1, i32.const opcode 0x41, signed LEB128).
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python3 - "$JS" "$WASM" <<'PY'
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import sys, re
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js_path, wasm_path = sys.argv[1], sys.argv[2]
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data = open(wasm_path, 'rb').read()
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def read_uleb(buf, pos):
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val = shift = 0
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while True:
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b = buf[pos]; pos += 1
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val |= (b & 0x7f) << shift
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shift += 7
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if not (b & 0x80):
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return val, pos
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def read_sleb(buf, pos):
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val = shift = 0
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while True:
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b = buf[pos]; pos += 1
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val |= (b & 0x7f) << shift
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shift += 7
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if not (b & 0x80):
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if b & 0x40:
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val |= (~0) << shift
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return val & 0xffffffff, pos
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# Walk sections looking for section id 6 (Global)
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pos = 8 # skip magic + version
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actual = None
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while pos < len(data):
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sid = data[pos]; pos += 1
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size, pos = read_uleb(data, pos)
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end = pos + size
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if sid == 6:
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count, p = read_uleb(data, pos)
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for gi in range(count):
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p += 2 # valtype + mutability
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opcode = data[p]; p += 1
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if opcode == 0x41: # i32.const
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val, p = read_sleb(data, p)
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if gi == 1:
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actual = val
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break
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p += 1 # skip end opcode
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break
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pos = end
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if actual is None:
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sys.stderr.write(
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'[post-build] WARN: could not parse global index 1 from wasm; '
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'skipping ___emscripten_embedded_file_data sync\n')
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sys.exit(0)
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js = open(js_path).read()
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m = re.search(r'Module\[.___emscripten_embedded_file_data.\]=(\d+)', js)
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if not m:
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# Emscripten may have fixed the stale-constant bug in a newer version.
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# Not fatal, but worth surfacing so we can drop this patch eventually.
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sys.stderr.write(
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'[post-build] INFO: ___emscripten_embedded_file_data not present; '
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'sync patch no longer applies (likely fixed upstream)\n')
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sys.exit(0)
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old = int(m.group(1))
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if old != actual:
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print(f'[post-build] Fixing ___emscripten_embedded_file_data: {old} -> {actual}')
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js = js.replace(
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f'Module["___emscripten_embedded_file_data"]={old}',
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f'Module["___emscripten_embedded_file_data"]={actual}',
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)
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open(js_path, 'w').write(js)
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PY
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echo "[post-build] Done."
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