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linker: detect duplicate exported definitions without imports #6750

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12 changes: 12 additions & 0 deletions source/link/linker.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -504,6 +504,18 @@ spv_result_t GetImportExportPairs(const MessageConsumer& consumer,
<< possible_export.second.name << "\".";
}

// Detect duplicate exported definitions (One Definition Rule violation).

@s-perron s-perron Jun 26, 2026

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Can you point to the "One definition rule"? When talking about linking, the ODR rule is a C++ rule that says a function can have multiple declarations, but they must all be the same. When the linker sees two definitions, it is allowed to pick one at random, and it will not change the semantics of the program.

Also, a C++-like ODR feature in part of SPIR-V.

You might want to change the comment to say that you cannot have multiple strong definitions.

// The existing check inside the import-matching loop below only catches
// duplicates when there is a corresponding import. This standalone check
// catches the case where multiple modules export the same symbol but no
// module imports it.
for (const auto& exp : exports) {
if (exp.second.size() > 1u)
return DiagnosticStream(position, consumer, "", SPV_ERROR_INVALID_BINARY)
<< "Too many external references, " << exp.second.size()
<< ", were found for \"" << exp.first << "\".";
}

// Find the import/export pairs
for (const auto& import : imports) {
std::vector<LinkageSymbolInfo> possible_exports;
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