[COFF] Fix reading variable-length encoded records

[aganea]

Summary

While reading Codeview records which contain variable-length encoded integers,
such as LF_BCLASS, LF_ENUMERATE, LF_MEMBER, LF_VBCLASS or LF_IVBCLASS,
the record's size would be improperly calculated in cases where the value was
indeed variable-length (>= LF_NUMERIC). This caused a bad alignement on the
next record, which would/might crash later on.

[rnk]

test/DebugInfo/COFF/enum_var.ll

1 ↗

(On Diff #140472)

I don't think this test exercises the fix. Only type stream merging and LLD exercise type index discovery.

[zturner]

We have a unit test called TypeIndexDiscoveryTest. Could go there.

[aganea]

My bad - I should have tested without the patch. Updated following @zturner's suggestion.

llvm/trunk/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp

constexpr uint32_t Sizes[] = {
       4,  // LF_REAL32
       8,  // LF_REAL64
       10, // LF_REAL80
       16, // LF_REAL128
       8,  // LF_QUADWORD
       8,  // LF_UQUADWORD
   };
 
-  return Sizes[N - LF_NUMERIC];
+  return 2 + Sizes[N - LF_NUMERIC];
 }
 
 static inline uint32_t getCStringLength(ArrayRef<uint8_t> Data) {
   const char *S = reinterpret_cast<const char *>(Data.data());
   return strlen(S) + 1;
 }
 
 static void handleMethodOverloadList(ArrayRef<uint8_t> Content,
case SymbolKind::S_GTHREAD32:
     break;
   case SymbolKind::S_FILESTATIC:
     Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_LOCAL:
     Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_REGISTER:
-    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type;
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_CONSTANT:
     Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_BPREL32:
   case SymbolKind::S_REGREL32:
     Refs.push_back({TiRefKind::TypeRef, 4, 1}); // Type
     break;

llvm/trunk/unittests/DebugInfo/CodeView/TypeIndexDiscoveryTest.cpp

TEST_F(TypeIndexIteratorTest, Precomp) {
   P.PrecompFilePath = "C:/precomp.obj";
 
   EndPrecompRecord EP(TypeRecordKind::EndPrecomp);
   EP.Signature = P.Signature;
 
   writeTypeRecords(P, EP);
   checkTypeReferences(0);
 }
+
+// This is a test for getEncodedIntegerLength()
+TEST_F(TypeIndexIteratorTest, VariableSizeIntegers) {
+  BaseClassRecord BaseClass1(MemberAccess::Public, TypeIndex(47), (uint64_t)-1);
+  BaseClassRecord BaseClass2(MemberAccess::Public, TypeIndex(48), 1);
+  writeFieldList(BaseClass1, BaseClass2);
+  checkTypeReferences(0, TypeIndex(47), TypeIndex(48));
+}
 No newline at end of file