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Fix PR22750: non-determinism causes assertion failure in DWARF generation

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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.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231100 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dario Domizioli
2015-03-03 18:40:53 +00:00
parent f5e27edc7b
commit 2a6c6e914a
1 changed files with 5 additions and 2 deletions
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7
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
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@ -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)));