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[wasm2js] Escape module names in generated JavaScript output #8377

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[wasm2js] Escape module names in generated JavaScript output #8377

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62 changes: 56 additions & 6 deletions src/wasm2js.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2628,6 +2628,55 @@ void Wasm2JSBuilder::addMemoryGrowFunc(Ref ast, Module* wasm) {
ast->push_back(memoryGrowFunc);
}

// Escape a string for safe inclusion in a JavaScript string literal.
// WebAssembly module/base names are arbitrary UTF-8 and may contain characters
// that are JS string metacharacters (quotes, backslashes, newlines, etc.).
static std::string escapeJSString(std::string_view str) {
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@tlively tlively Feb 26, 2026

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Could we use printEscapedJSON from support/string.h instead? If not, that would be a better place to add new escaping logic.

std::string result;
result.reserve(str.size());
for (size_t i = 0; i < str.size(); i++) {
unsigned char c = str[i];
switch (c) {
case '\\':
result += "\\\\";
break;
case '\'':
result += "\\'";
break;
case '"':
result += "\\\"";
break;
case '\n':
result += "\\n";
break;
case '\r':
result += "\\r";
break;
default:
// Check for U+2028 (LINE SEPARATOR) and U+2029 (PARAGRAPH SEPARATOR)
// which are valid in JSON strings but act as line terminators in JS.
// They are encoded as E2 80 A8 and E2 80 A9 in UTF-8.
if (c == 0xE2 && i + 2 < str.size() &&
static_cast<unsigned char>(str[i + 1]) == 0x80) {
unsigned char c2 = str[i + 2];
if (c2 == 0xA8) {
result += "\\u2028";
i += 2;
break;
}
if (c2 == 0xA9) {
result += "\\u2029";
i += 2;
break;
}
}
result += static_cast<char>(c);
break;
}
}
return result;
}

// Wasm2JSBuilder emits the core of the module - the functions etc. that would
// be the asm.js function in an asm.js world. This class emits the rest of the
// "glue" around that.
Expand Down Expand Up @@ -2708,7 +2757,7 @@ void Wasm2JSGlue::emitPreES6() {
baseModuleMap[base] = module;
if (seenModules.count(module) == 0) {
out << "import * as " << asmangle(module.toString()) << " from '"
<< module << "';\n";
<< escapeJSString(module.toString()) << "';\n";
seenModules.insert(module);
}
};
Expand Down Expand Up @@ -2770,7 +2819,7 @@ void Wasm2JSGlue::emitPostES6() {
if (seenModules.count(import->module) > 0) {
return;
}
out << " \"" << import->module
out << " \"" << escapeJSString(import->module.toString())
<< "\": " << asmangle(import->module.toString()) << ",\n";
seenModules.insert(import->module);
});
Expand All @@ -2781,7 +2830,7 @@ void Wasm2JSGlue::emitPostES6() {
if (ABI::wasm2js::isHelper(import->base)) {
return;
}
out << " \"" << import->module << "\": {\n";
out << " \"" << escapeJSString(import->module.toString()) << "\": {\n";
out << " " << asmangle(import->base.toString()) << ": { buffer : mem"
<< moduleName.str << " }\n";
out << " },\n";
Expand All @@ -2796,7 +2845,7 @@ void Wasm2JSGlue::emitPostES6() {
if (seenModules.count(import->module) > 0) {
return;
}
out << " \"" << import->module
out << " \"" << escapeJSString(import->module.toString())
<< "\": " << asmangle(import->module.toString()) << ",\n";
seenModules.insert(import->module);
});
Expand Down Expand Up @@ -2900,8 +2949,9 @@ void Wasm2JSGlue::emitMemory() {
if (auto* get = segment.offset->dynCast<GlobalGet>()) {
auto internalName = get->name;
auto importedGlobal = wasm.getGlobal(internalName);
return std::string("imports['") + importedGlobal->module.toString() +
"']['" + importedGlobal->base.toString() + "']";
return std::string("imports['") +
escapeJSString(importedGlobal->module.toString()) + "']['" +
escapeJSString(importedGlobal->base.toString()) + "']";
}
Fatal() << "non-constant offsets aren't supported yet\n";
};
Expand Down
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