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llvm::MachO::InterfaceFile::symbols is non-deterministic #97127

Open MaskRay opened 1 week ago

MaskRay commented 1 week ago

https://github.com/llvm/llvm-project/blob/0991bd7887a313d4d6bb66ca44d11939ad71b660/llvm/include/llvm/TextAPI/InterfaceFile.h#L447 std::unique_ptr<SymbolSet> SymbolsSet; is implemented as a using SymbolsMapType = llvm::DenseMap<SymbolsMapKey, Symbol *>;, which has a non-deterministic iteration order in LLVM_ENABLE_ABI_BREAKING_CHECKS=on builds (hash_combine(hash_value(Key.Kind), hash_value(Key.Name)) uses a non-deterministic seed #96282).

This hade made lld/test/MachO/dead-strip.s flaky until I fixed by it with ceeea9193726ff3ceeee48e0e121ac25ac12cef0. The fix is imperfect, since it's better for llvm/include/llvm/TextAPI/InterfaceFile.h to provide a stable iteration order.

llvmbot commented 1 week ago

@llvm/issue-subscribers-lld-macho

Author: Fangrui Song (MaskRay)

https://github.com/llvm/llvm-project/blob/0991bd7887a313d4d6bb66ca44d11939ad71b660/llvm/include/llvm/TextAPI/InterfaceFile.h#L447 `std::unique_ptr<SymbolSet> SymbolsSet;` is implemented as a `using SymbolsMapType = llvm::DenseMap<SymbolsMapKey, Symbol *>;`, which has a non-deterministic iteration order in `LLVM_ENABLE_ABI_BREAKING_CHECKS=on` builds (`hash_combine(hash_value(Key.Kind), hash_value(Key.Name))` uses a non-deterministic seed #96282). This hade made `lld/test/MachO/dead-strip.s` flaky until I fixed by it with ceeea9193726ff3ceeee48e0e121ac25ac12cef0. The fix is imperfect, since it's better for `llvm/include/llvm/TextAPI/InterfaceFile.h` to provide a stable iteration order.
MaskRay commented 1 week ago

@cyndyishida @int3

tgymnich commented 2 days ago

here is a draft addressing the issue using std::map https://github.com/llvm/llvm-project/pull/97615