[Lldb-commits] [PATCH] D134493: [lldb][TypeSystemClang] Deduce lldb::eEncodingUint for unsigned enum types

[Michael Buch via Phabricator via lldb-commits]

Michael137 created this revision.
Michael137 added reviewers: aprantl, jingham.
Herald added a project: All.
Michael137 requested review of this revision.
Herald added a project: LLDB.
Herald added a subscriber: lldb-commits.

The motivating issue was the following:

  $ cat main.cpp
  enum class EnumVals : uint16_t {
      VAL1 = 0
  };
  
  struct Foo {
      EnumVals b1 : 8;
  };
  
  int main() {
      Foo f{.b1 = (EnumVals)8};
  
      return 0; // Break here
  }
  
  (lldb) script
  >>> 
lldb.frame.FindVariable("f").GetChildMemberWithName("b1").GetValueAsUnsigned()
  4294967288

In the above example we observe a unsigned integer wrap-around
because we sign-extended the bit-fields underlying Scalar value
before casting it to an unsigned. The sign extension occurs because
we don't mark `APSInt::IsUnsigned == true` correctly when extracting
the value from memory (in Value::ResolveValue).

This patch corrects `GetEncoding` to account for unsigned enum types.
With this change the Scalar would be zero-extended instead.

This is mainly a convenience fix which well-formed code wouldn't
encounter.

rdar://99785324


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134493

Files:
  lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp


Index: lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
===================================================================
--- lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -5097,7 +5097,9 @@
   case clang::Type::Record:
     break;
   case clang::Type::Enum:
-    return lldb::eEncodingSint;
+    return qual_type->isUnsignedIntegerOrEnumerationType()
+               ? lldb::eEncodingUint
+               : lldb::eEncodingSint;
   case clang::Type::DependentSizedArray:
   case clang::Type::DependentSizedExtVector:
   case clang::Type::UnresolvedUsing:



Index: lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
===================================================================
--- lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -5097,7 +5097,9 @@
   case clang::Type::Record:
     break;
   case clang::Type::Enum:
-    return lldb::eEncodingSint;
+    return qual_type->isUnsignedIntegerOrEnumerationType()
+               ? lldb::eEncodingUint
+               : lldb::eEncodingSint;
   case clang::Type::DependentSizedArray:
   case clang::Type::DependentSizedExtVector:
   case clang::Type::UnresolvedUsing:

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