From 5f7008a688a6c14958932aefdd3ec777d55f9fe0 Mon Sep 17 00:00:00 2001 From: Dario Domizioli Date: Tue, 3 Mar 2015 18:40:53 +0000 Subject: [PATCH] Fix PR22750: non-determinism causes assertion failure in DWARF generation The cause of the issue is the interaction of two factors: 1) When generating a DW_TAG_imported_declaration DIE which imports another imported declaration, the code in AsmPrinter/DwarfCompileUnit.cpp asserts that the second imported declaration must already have a DIE. 2) There is a non-determinism in the order in which imported declarations within the same scope are processed. Because of the non-determinism (2), it is possible that an imported declaration is processed before another one it depends on, breaking the assumption in (1). The source of the non-determinism is that the imported declaration DIDescriptors are sorted by scope in DwarfDebug::beginModule(); however that sort is not a stable_sort, therefore the order of the declarations within the same scope is not preserved. The attached patch changes the std::sort to a std::stable_sort and it fixes the problem. Test omitted due to it being non-deterministic and depending on the implementation of std::sort. llvm-svn: 231100 --- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp index 1cc0581..6367694 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp @@ -477,8 +477,11 @@ void DwarfDebug::beginModule() { ScopesWithImportedEntities.push_back(std::make_pair( DIImportedEntity(ImportedEntities.getElement(i)).getContext(), ImportedEntities.getElement(i))); - std::sort(ScopesWithImportedEntities.begin(), - ScopesWithImportedEntities.end(), less_first()); + // Stable sort to preserve the order of appearance of imported entities. + // This is to avoid out-of-order processing of interdependent declarations + // within the same scope, e.g. { namespace A = base; namespace B = A; } + std::stable_sort(ScopesWithImportedEntities.begin(), + ScopesWithImportedEntities.end(), less_first()); DIArray GVs = CUNode.getGlobalVariables(); for (unsigned i = 0, e = GVs.getNumElements(); i != e; ++i) CU.getOrCreateGlobalVariableDIE(DIGlobalVariable(GVs.getElement(i))); -- 2.7.4