[codeview] Fix buggy BeginIndexMapSize assertion

This assert is just trying to test that processing each record adds
exactly one entry to the index map. The assert logic was wrong when the
first record in the type stream was a field list.

I've simplified the code by moving the LF_FIELDLIST-specific logic into
the callback for that record type.

llvm-svn: 299035

llvm/lib/DebugInfo/CodeView/TypeStreamMerger.cpp

@@ -126,8 +126,11 @@ private:
   FieldListRecordBuilder FieldListBuilder;
   TypeServerHandler *Handler;
 
-  bool IsInFieldList = false;
+#ifndef NDEBUG
+  /// Track the size of the index map in visitTypeBegin so we can check it in
+  /// visitTypeEnd.
   size_t BeginIndexMapSize = 0;
+#endif
 
   /// Map from source type index to destination type index. Indexed by source
   /// type index minus 0x1000.
@@ -137,26 +140,19 @@ private:
 } // end anonymous namespace
 
 Error TypeStreamMerger::visitTypeBegin(CVRecord<TypeLeafKind> &Rec) {
-  if (Rec.Type == TypeLeafKind::LF_FIELDLIST) {
-    assert(!IsInFieldList);
-    IsInFieldList = true;
-    FieldListBuilder.begin();
-  } else
-    BeginIndexMapSize = IndexMap.size();
+#ifndef NDEBUG
+  BeginIndexMapSize = IndexMap.size();
+#endif
   return Error::success();
 }
 
 Error TypeStreamMerger::visitTypeEnd(CVRecord<TypeLeafKind> &Rec) {
-  if (Rec.Type == TypeLeafKind::LF_FIELDLIST) {
-    TypeIndex Index = FieldListBuilder.end();
-    IndexMap.push_back(Index);
-    IsInFieldList = false;
-  }
+  assert(IndexMap.size() == BeginIndexMapSize + 1 &&
+         "visitKnownRecord should add one index map entry");
   return Error::success();
 }
 
 Error TypeStreamMerger::visitMemberEnd(CVMemberRecord &Rec) {
-  assert(IndexMap.size() == BeginIndexMapSize + 1);
   return Error::success();
 }
 
@@ -322,9 +318,12 @@ Error TypeStreamMerger::visitKnownRecord(CVType &,
 
 Error TypeStreamMerger::visitKnownRecord(CVType &, FieldListRecord &R) {
   // Visit the members inside the field list.
+  FieldListBuilder.begin();
   CVTypeVisitor Visitor(*this);
   if (auto EC = Visitor.visitFieldListMemberStream(R.Data))
     return EC;
+  TypeIndex Index = FieldListBuilder.end();
+  IndexMap.push_back(Index);
   return Error::success();
 }
 

llvm/test/tools/llvm-readobj/codeview-merging-anon.test

@@ -0,0 +1,29 @@
+# Test what happens when the first type record (0x1000) is a LF_FIELDLIST
+# record.
+
+# Steps to regenerate input:
+# $ cat t.c
+# struct { int x; } o;
+# $ cl -Z7 t.c
+
+RUN: llvm-readobj -codeview %S/Inputs/codeview-merging-anon.obj | FileCheck %s
+RUN: llvm-readobj -codeview-merged-types %S/Inputs/codeview-merging-anon.obj | FileCheck %s
+
+CHECK-LABEL:  FieldList (0x1000) {
+CHECK-NEXT:     TypeLeafKind: LF_FIELDLIST (0x1203)
+CHECK-NEXT:     DataMember {
+CHECK-NEXT:       TypeLeafKind: LF_MEMBER (0x150D)
+CHECK-NEXT:       AccessSpecifier: Public (0x3)
+CHECK-NEXT:       Type: int (0x74)
+CHECK-NEXT:       FieldOffset: 0x0
+CHECK-NEXT:       Name: x
+CHECK-NEXT:     }
+CHECK-NEXT:   }
+CHECK-LABEL:  Struct (0x1001) {
+CHECK:          TypeLeafKind: LF_STRUCTURE (0x1505)
+CHECK:          MemberCount: 1
+CHECK:          FieldList: <field list> (0x1000)
+CHECK:          Name: <unnamed-tag>
+CHECK:          LinkageName: .?AU<unnamed-tag>@@
+CHECK:        }
+CHECK-LABEL:  StringId