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Binary Reading: Don't pick internal names for things that overlap with the name section #7700

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Binary Reading: Don't pick internal names for things that overlap with the name section #7700

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15 changes: 9 additions & 6 deletions src/wasm/wasm-binary.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2518,12 +2518,15 @@ getOrMakeName(const std::unordered_map<Index, Name>& nameMap,
Name name,
std::unordered_set<Name>& usedNames) {
if (auto it = nameMap.find(i); it != nameMap.end()) {
return {it->second, true};
} else {
auto valid = Names::getValidNameGivenExisting(name, usedNames);
usedNames.insert(valid);
return {valid, false};
}
// We found a name in the names section. Use it, and also note it as used
// so we don't generate such a name below, later.
Comment on lines +2521 to +2522
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Is there anything stopping us from generating a name below and later running into it in the names section?

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I believe this code aims to avoid that, be pre-populating the names:

binaryen/src/wasm/wasm-binary.cpp

Lines 3010 to 3020 in efcf2dc

void WasmBinaryReader::readFunctionSignatures() {
size_t num = getU32LEB();
auto numImports = wasm.functions.size();
std::unordered_set<Name> usedNames;
for (auto& [index, name] : functionNames) {
if (index >= num + numImports) {
std::cerr << "warning: function index out of bounds in name section: "
<< name << " at index " << index << '\n';
}
usedNames.insert(name);
}

But that raises the question of why that didn't fix this issue. Unfortunately, I can only reproduce this with an experimental pass not yet in a PR, so I don't have a good testcase. Anyhow, let's hold off on this until that PR is ready.

auto mappedName = it->second;
usedNames.insert(mappedName);
return {mappedName, true};
}
auto valid = Names::getValidNameGivenExisting(name, usedNames);
usedNames.insert(valid);
return {valid, false};
}

void WasmBinaryReader::readMemories() {
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