[Lldb-commits] [PATCH] D142683: Manual DWARF index: don't skip over -gmodules debug info

[Adrian Prantl via Phabricator via lldb-commits]

aprantl updated this revision to Diff 492782.
aprantl added a comment.

I added an unambiguous check for DWARF5+. The remaining incorrectly handled case is a DWARF4 + GNU fission extension where the .dwo file has been deleted. Is there any harm in indexing the skeleton in that case? It shouldn't be able to interfere with the declarations in the (missing) .dwo file in that case, right?
Let me know if this is not enough and I'll try finding another heuristic that we could apply here.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142683/new/

https://reviews.llvm.org/D142683

Files:
  lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
  lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
  lldb/test/Shell/SymbolFile/DWARF/Inputs/pch.h
  lldb/test/Shell/SymbolFile/DWARF/clang-gmodules-type-lookup.c


Index: lldb/test/Shell/SymbolFile/DWARF/clang-gmodules-type-lookup.c
===================================================================
--- /dev/null
+++ lldb/test/Shell/SymbolFile/DWARF/clang-gmodules-type-lookup.c
@@ -0,0 +1,18 @@
+// UNSUPPORTED: system-windows
+
+// Test that LLDB can follow DWO links produced by -gmodules debug
+// info to find a type in a precompiled header.
+// 
+// RUN: %clangxx_host -g -gmodules -fmodules -std=c99 -x c-header %S/Inputs/pch.h -g -c -o %t.pch
+// RUN: %clangxx_host -g -gmodules -fmodules -std=c99 -x c -include-pch %t.pch %s -c -o %t.o
+// RUN: %clangxx_host %t.o -o %t.exe
+// RUN: lldb-test symbols -dump-clang-ast -find type --language=C99 \
+// RUN:   -compiler-context 'AnyModule:*,Struct:TypeFromPCH' %t.exe | FileCheck %s
+
+anchor_t anchor;
+
+int main(int argc, char **argv) { return 0; }
+
+// CHECK: Found 1 type
+// CHECK: "TypeFromPCH"
+// CHECK: FieldDecl {{.*}} field
Index: lldb/test/Shell/SymbolFile/DWARF/Inputs/pch.h
===================================================================
--- /dev/null
+++ lldb/test/Shell/SymbolFile/DWARF/Inputs/pch.h
@@ -0,0 +1,5 @@
+typedef int anchor_t;
+
+struct TypeFromPCH {
+  int field;
+};
Index: lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/ManualDWARFIndex.cpp
@@ -162,12 +162,13 @@
   // though as some functions have template parameter types and other things
   // that cause extra copies of types to be included, but we should find these
   // types in the .dwo file only as methods could have return types removed and
-  // we don't have to index incomplete types from the skeletone compile unit.
+  // we don't have to index incomplete types from the skeleton compile unit.
   if (unit.GetDWOId()) {
+    // Index the .dwo or dwp instead of the skeleton unit.
     if (SymbolFileDWARFDwo *dwo_symbol_file = unit.GetDwoSymbolFile()) {
       // Type units in a dwp file are indexed separately, so we just need to
-      // process the split unit here. However, if the split unit is in a dwo file,
-      // then we need to process type units here.
+      // process the split unit here. However, if the split unit is in a dwo
+      // file, then we need to process type units here.
       if (dwo_symbol_file == dwp) {
         IndexUnitImpl(unit.GetNonSkeletonUnit(), cu_language, set);
       } else {
@@ -175,11 +176,18 @@
         for (size_t i = 0; i < dwo_info.GetNumUnits(); ++i)
           IndexUnitImpl(*dwo_info.GetUnitAtIndex(i), cu_language, set);
       }
+      return;
     }
-  } else {
-    // We either have a normal compile unit which we want to index.
-    IndexUnitImpl(unit, cu_language, set);
+    // This was a DWARF5 skeleton CU and the .dwo file couldn't be located.
+    if (unit.IsSkeletonUnit())
+      return;
+
+    // Otherwise, the unit has a dwo_id, but this isn't a .dwo
+    // skeleton unit, so the assumption is that this is a file
+    // produced by -gmodules and that we want to index it.
   }
+  // We have a normal compile unit which we want to index.
+  IndexUnitImpl(unit, cu_language, set);
 }
 
 void ManualDWARFIndex::IndexUnitImpl(DWARFUnit &unit,
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
@@ -223,6 +223,8 @@
 
   uint8_t GetUnitType() const { return m_header.GetUnitType(); }
   bool IsTypeUnit() const { return m_header.IsTypeUnit(); }
+  /// Note that this check only works for DWARF5+.
+  bool IsSkeletonUnit() const { return GetUnitType() == llvm::dwarf::DW_UT_skeleton; }
 
   std::optional<uint64_t> GetStringOffsetSectionItem(uint32_t index) const;
 


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