[Lldb-commits] [lldb] [llvm] [lldb] Return an llvm::Expected from DWARFExpression::Evaluate (NFCI) (PR #94420)

Jonas Devlieghere via lldb-commits lldb-commits at lists.llvm.org
Wed Jun 5 09:31:03 PDT 2024


https://github.com/JDevlieghere updated https://github.com/llvm/llvm-project/pull/94420

>From 22bb28a5e3fc84c75e1013c3b0c15654e7b786da Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Tue, 4 Jun 2024 17:04:15 -0700
Subject: [PATCH 1/5] [Support] Add variadic createStringError overload (NFC)

---
 llvm/include/llvm/Support/Error.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/llvm/include/llvm/Support/Error.h b/llvm/include/llvm/Support/Error.h
index 662c3ea46e3c1..1fa0d8cb709cc 100644
--- a/llvm/include/llvm/Support/Error.h
+++ b/llvm/include/llvm/Support/Error.h
@@ -1277,6 +1277,11 @@ inline Error createStringError(const Twine &S) {
   return createStringError(llvm::inconvertibleErrorCode(), S);
 }
 
+template <typename... Ts>
+inline Error createStringError(char const *Fmt, const Ts &...Vals) {
+  return createStringError(llvm::inconvertibleErrorCode(), Fmt, Vals...);
+}
+
 template <typename... Ts>
 inline Error createStringError(std::errc EC, char const *Fmt,
                                const Ts &... Vals) {

>From d5c288ddb9473a52a8635a32d3a5cc057c9cb986 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Tue, 4 Jun 2024 19:04:07 -0700
Subject: [PATCH 2/5] [lldb] Return an llvm::Expected from
 DWARFExpression::Evaluate (NFCI)

Change the interface of DWARFExpression::Evaluate and
DWARFExpressionList::Evaluate to return an llvm::Expected instead of a
boolean. This eliminates the Status output parameter and improves error
handling.
---
 .../include/lldb/Expression/DWARFExpression.h |  13 +-
 .../lldb/Expression/DWARFExpressionList.h     |  10 +-
 lldb/source/Core/ValueObjectVariable.cpp      |   8 +-
 lldb/source/Expression/DWARFExpression.cpp    | 747 +++++++-----------
 .../source/Expression/DWARFExpressionList.cpp |  28 +-
 .../SymbolFile/DWARF/DWARFASTParserClang.cpp  |  20 +-
 .../SymbolFile/DWARF/SymbolFileDWARF.cpp      |  16 +-
 lldb/source/Symbol/Function.cpp               |  17 +-
 lldb/source/Target/RegisterContextUnwind.cpp  |  23 +-
 lldb/source/Target/StackFrame.cpp             |  19 +-
 .../Expression/DWARFExpressionTest.cpp        |  78 +-
 11 files changed, 401 insertions(+), 578 deletions(-)

diff --git a/lldb/include/lldb/Expression/DWARFExpression.h b/lldb/include/lldb/Expression/DWARFExpression.h
index 1d85308d1caa7..e85ba464dea6b 100644
--- a/lldb/include/lldb/Expression/DWARFExpression.h
+++ b/lldb/include/lldb/Expression/DWARFExpression.h
@@ -132,13 +132,12 @@ class DWARFExpression {
   /// \return
   ///     True on success; false otherwise.  If error_ptr is non-NULL,
   ///     details of the failure are provided through it.
-  static bool Evaluate(ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
-                       lldb::ModuleSP module_sp, const DataExtractor &opcodes,
-                       const plugin::dwarf::DWARFUnit *dwarf_cu,
-                       const lldb::RegisterKind reg_set,
-                       const Value *initial_value_ptr,
-                       const Value *object_address_ptr, Value &result,
-                       Status *error_ptr);
+  static llvm::Expected<Value>
+  Evaluate(ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
+           lldb::ModuleSP module_sp, const DataExtractor &opcodes,
+           const plugin::dwarf::DWARFUnit *dwarf_cu,
+           const lldb::RegisterKind reg_set, const Value *initial_value_ptr,
+           const Value *object_address_ptr);
 
   static bool ParseDWARFLocationList(const plugin::dwarf::DWARFUnit *dwarf_cu,
                                      const DataExtractor &data,
diff --git a/lldb/include/lldb/Expression/DWARFExpressionList.h b/lldb/include/lldb/Expression/DWARFExpressionList.h
index c2218ad4af0a7..f711a1cbe9bbd 100644
--- a/lldb/include/lldb/Expression/DWARFExpressionList.h
+++ b/lldb/include/lldb/Expression/DWARFExpressionList.h
@@ -9,6 +9,7 @@
 #ifndef LLDB_EXPRESSION_DWARFEXPRESSIONLIST_H
 #define LLDB_EXPRESSION_DWARFEXPRESSIONLIST_H
 
+#include "lldb/Core/Value.h"
 #include "lldb/Expression/DWARFExpression.h"
 #include "lldb/Utility/RangeMap.h"
 #include "lldb/lldb-private.h"
@@ -113,10 +114,11 @@ class DWARFExpressionList {
 
   void SetModule(const lldb::ModuleSP &module) { m_module_wp = module; }
 
-  bool Evaluate(ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
-                lldb::addr_t func_load_addr, const Value *initial_value_ptr,
-                const Value *object_address_ptr, Value &result,
-                Status *error_ptr) const;
+  llvm::Expected<Value> Evaluate(ExecutionContext *exe_ctx,
+                                 RegisterContext *reg_ctx,
+                                 lldb::addr_t func_load_addr,
+                                 const Value *initial_value_ptr,
+                                 const Value *object_address_ptr) const;
 
 private:
   // RangeDataVector requires a comparator for DWARFExpression, but it doesn't
diff --git a/lldb/source/Core/ValueObjectVariable.cpp b/lldb/source/Core/ValueObjectVariable.cpp
index 67d71c90a959d..51eb11d3a189e 100644
--- a/lldb/source/Core/ValueObjectVariable.cpp
+++ b/lldb/source/Core/ValueObjectVariable.cpp
@@ -164,8 +164,11 @@ bool ValueObjectVariable::UpdateValue() {
                 target);
     }
     Value old_value(m_value);
-    if (expr_list.Evaluate(&exe_ctx, nullptr, loclist_base_load_addr, nullptr,
-                           nullptr, m_value, &m_error)) {
+    llvm::Expected<Value> maybe_value = expr_list.Evaluate(
+        &exe_ctx, nullptr, loclist_base_load_addr, nullptr, nullptr);
+
+    if (maybe_value) {
+      m_value = *maybe_value;
       m_resolved_value = m_value;
       m_value.SetContext(Value::ContextType::Variable, variable);
 
@@ -246,6 +249,7 @@ bool ValueObjectVariable::UpdateValue() {
 
       SetValueIsValid(m_error.Success());
     } else {
+      m_error = maybe_value.takeError();
       // could not find location, won't allow editing
       m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
     }
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 7473bb8255d0a..5c7ab49410efe 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -541,12 +541,12 @@ bool DWARFExpression::LinkThreadLocalStorage(
   return true;
 }
 
-static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
-                                       ExecutionContext *exe_ctx,
-                                       RegisterContext *reg_ctx,
-                                       const DataExtractor &opcodes,
-                                       lldb::offset_t &opcode_offset,
-                                       Status *error_ptr, Log *log) {
+static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
+                                              ExecutionContext *exe_ctx,
+                                              RegisterContext *reg_ctx,
+                                              const DataExtractor &opcodes,
+                                              lldb::offset_t &opcode_offset,
+                                              Log *log) {
   // DW_OP_entry_value(sub-expr) describes the location a variable had upon
   // function entry: this variable location is presumed to be optimized out at
   // the current PC value.  The caller of the function may have call site
@@ -593,16 +593,15 @@ static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
 
   // 1. Find the function which pushed the current frame onto the stack.
   if ((!exe_ctx || !exe_ctx->HasTargetScope()) || !reg_ctx) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no exe/reg context");
-    return false;
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no exe/reg context");
   }
 
   StackFrame *current_frame = exe_ctx->GetFramePtr();
   Thread *thread = exe_ctx->GetThreadPtr();
-  if (!current_frame || !thread) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no current frame/thread");
-    return false;
-  }
+  if (!current_frame || !thread)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no current frame/thread");
 
   Target &target = exe_ctx->GetTargetRef();
   StackFrameSP parent_frame = nullptr;
@@ -634,25 +633,23 @@ static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     break;
   }
   if (!parent_frame || !parent_frame->GetRegisterContext()) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no parent frame with reg ctx");
-    return false;
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no parent frame with reg ctx");
   }
 
   Function *parent_func =
       parent_frame->GetSymbolContext(eSymbolContextFunction).function;
-  if (!parent_func) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no parent function");
-    return false;
-  }
+  if (!parent_func)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no parent function");
 
   // 2. Find the call edge in the parent function responsible for creating the
   //    current activation.
   Function *current_func =
       current_frame->GetSymbolContext(eSymbolContextFunction).function;
-  if (!current_func) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no current function");
-    return false;
-  }
+  if (!current_func)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no current function");
 
   CallEdge *call_edge = nullptr;
   ModuleList &modlist = target.GetImages();
@@ -663,17 +660,16 @@ static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     // produced by an ambiguous tail call. In this case, refuse to proceed.
     call_edge = parent_func->GetCallEdgeForReturnAddress(return_pc, target);
     if (!call_edge) {
-      LLDB_LOG(log,
-               "Evaluate_DW_OP_entry_value: no call edge for retn-pc = {0:x} "
-               "in parent frame {1}",
-               return_pc, parent_func->GetName());
-      return false;
+      return llvm::createStringError(llvm::formatv(
+          "Evaluate_DW_OP_entry_value: no call edge for retn-pc = {0:x} "
+          "in parent frame {1}",
+          return_pc, parent_func->GetName()));
     }
     Function *callee_func = call_edge->GetCallee(modlist, parent_exe_ctx);
     if (callee_func != current_func) {
-      LLDB_LOG(log, "Evaluate_DW_OP_entry_value: ambiguous call sequence, "
-                    "can't find real parent frame");
-      return false;
+      return llvm::createStringError(
+          "Evaluate_DW_OP_entry_value: ambiguous call sequence, "
+          "can't find real parent frame");
     }
   } else {
     // The StackFrameList solver machinery has deduced that an unambiguous tail
@@ -686,21 +682,19 @@ static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
       }
     }
   }
-  if (!call_edge) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: no unambiguous edge from parent "
-                  "to current function");
-    return false;
-  }
+  if (!call_edge)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no unambiguous edge from parent "
+        "to current function");
 
   // 3. Attempt to locate the DW_OP_entry_value expression in the set of
   //    available call site parameters. If found, evaluate the corresponding
   //    parameter in the context of the parent frame.
   const uint32_t subexpr_len = opcodes.GetULEB128(&opcode_offset);
   const void *subexpr_data = opcodes.GetData(&opcode_offset, subexpr_len);
-  if (!subexpr_data) {
-    LLDB_LOG(log, "Evaluate_DW_OP_entry_value: subexpr could not be read");
-    return false;
-  }
+  if (!subexpr_data)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: subexpr could not be read");
 
   const CallSiteParameter *matched_param = nullptr;
   for (const CallSiteParameter &param : call_edge->GetCallSiteParameters()) {
@@ -726,28 +720,27 @@ static bool Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
       break;
     }
   }
-  if (!matched_param) {
-    LLDB_LOG(log,
-             "Evaluate_DW_OP_entry_value: no matching call site param found");
-    return false;
-  }
+  if (!matched_param)
+    return llvm::createStringError(
+        "Evaluate_DW_OP_entry_value: no matching call site param found");
 
   // TODO: Add support for DW_OP_push_object_address within a DW_OP_entry_value
   // subexpresion whenever llvm does.
-  Value result;
   const DWARFExpressionList &param_expr = matched_param->LocationInCaller;
-  if (!param_expr.Evaluate(&parent_exe_ctx,
-                           parent_frame->GetRegisterContext().get(),
-                           LLDB_INVALID_ADDRESS,
-                           /*initial_value_ptr=*/nullptr,
-                           /*object_address_ptr=*/nullptr, result, error_ptr)) {
+
+  llvm::Expected<Value> maybe_result = param_expr.Evaluate(
+      &parent_exe_ctx, parent_frame->GetRegisterContext().get(),
+      LLDB_INVALID_ADDRESS,
+      /*initial_value_ptr=*/nullptr,
+      /*object_address_ptr=*/nullptr);
+  if (!maybe_result) {
     LLDB_LOG(log,
              "Evaluate_DW_OP_entry_value: call site param evaluation failed");
-    return false;
+    return maybe_result.takeError();
   }
 
-  stack.push_back(result);
-  return true;
+  stack.push_back(*maybe_result);
+  return llvm::Error::success();
 }
 
 namespace {
@@ -862,19 +855,15 @@ static Scalar DerefSizeExtractDataHelper(uint8_t *addr_bytes,
     return addr_data.GetAddress(&addr_data_offset);
 }
 
-bool DWARFExpression::Evaluate(
+llvm::Expected<Value> DWARFExpression::Evaluate(
     ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
     lldb::ModuleSP module_sp, const DataExtractor &opcodes,
     const DWARFUnit *dwarf_cu, const lldb::RegisterKind reg_kind,
-    const Value *initial_value_ptr, const Value *object_address_ptr,
-    Value &result, Status *error_ptr) {
+    const Value *initial_value_ptr, const Value *object_address_ptr) {
 
-  if (opcodes.GetByteSize() == 0) {
-    if (error_ptr)
-      error_ptr->SetErrorString(
-          "no location, value may have been optimized out");
-    return false;
-  }
+  if (opcodes.GetByteSize() == 0)
+    return llvm::createStringError(
+        "no location, value may have been optimized out");
   std::vector<Value> stack;
 
   Process *process = nullptr;
@@ -994,11 +983,9 @@ bool DWARFExpression::Evaluate(
     // retrieved from the dereferenced address is the size of an address on the
     // target machine.
     case DW_OP_deref: {
-      if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString("Expression stack empty for DW_OP_deref.");
-        return false;
-      }
+      if (stack.empty())
+        return llvm::createStringError(
+            "Expression stack empty for DW_OP_deref.");
       Value::ValueType value_type = stack.back().GetValueType();
       switch (value_type) {
       case Value::ValueType::HostAddress: {
@@ -1013,11 +1000,12 @@ bool DWARFExpression::Evaluate(
             LLDB_INVALID_ADDRESS);
 
         Address so_addr;
+        Status load_err;
         auto maybe_load_addr = ResolveLoadAddress(
-            exe_ctx, module_sp, error_ptr, "DW_OP_deref", file_addr, so_addr);
+            exe_ctx, module_sp, &load_err, "DW_OP_deref", file_addr, so_addr);
 
         if (!maybe_load_addr)
-          return false;
+          return load_err.ToError();
 
         stack.back().GetScalar() = *maybe_load_addr;
         // Fall through to load address promotion code below.
@@ -1041,30 +1029,22 @@ bool DWARFExpression::Evaluate(
               stack.back().GetScalar() = pointer_value;
               stack.back().ClearContext();
             } else {
-              if (error_ptr)
-                error_ptr->SetErrorStringWithFormat(
-                    "Failed to dereference pointer from 0x%" PRIx64
-                    " for DW_OP_deref: %s\n",
-                    pointer_addr, error.AsCString());
-              return false;
+              return llvm::createStringError(
+                  "Failed to dereference pointer from 0x%" PRIx64
+                  " for DW_OP_deref: %s\n",
+                  pointer_addr, error.AsCString());
             }
           } else {
-            if (error_ptr)
-              error_ptr->SetErrorString("NULL process for DW_OP_deref.\n");
-            return false;
+            return llvm::createStringError("NULL process for DW_OP_deref.\n");
           }
         } else {
-          if (error_ptr)
-            error_ptr->SetErrorString(
-                "NULL execution context for DW_OP_deref.\n");
-          return false;
+          return llvm::createStringError(
+              "NULL execution context for DW_OP_deref.\n");
         }
         break;
 
       case Value::ValueType::Invalid:
-        if (error_ptr)
-          error_ptr->SetErrorString("Invalid value type for DW_OP_deref.\n");
-        return false;
+        return llvm::createStringError("Invalid value type for DW_OP_deref.\n");
       }
 
     } break;
@@ -1083,18 +1063,13 @@ bool DWARFExpression::Evaluate(
     // expression stack.
     case DW_OP_deref_size: {
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack empty for DW_OP_deref_size.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack empty for DW_OP_deref_size.");
       }
       uint8_t size = opcodes.GetU8(&offset);
       if (size > 8) {
-        if (error_ptr)
-              error_ptr->SetErrorStringWithFormat(
-                  "Invalid address size for DW_OP_deref_size: %d\n",
-                  size);
-        return false;
+        return llvm::createStringError(
+            "Invalid address size for DW_OP_deref_size: %d\n", size);
       }
       Value::ValueType value_type = stack.back().GetValueType();
       switch (value_type) {
@@ -1142,13 +1117,14 @@ bool DWARFExpression::Evaluate(
         auto file_addr =
             stack.back().GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
         Address so_addr;
+        Status resolve_err;
         auto maybe_load_addr =
-            ResolveLoadAddress(exe_ctx, module_sp, error_ptr,
-                                      "DW_OP_deref_size", file_addr, so_addr,
-                                      /*check_sectionoffset=*/true);
+            ResolveLoadAddress(exe_ctx, module_sp, &resolve_err,
+                               "DW_OP_deref_size", file_addr, so_addr,
+                               /*check_sectionoffset=*/true);
 
         if (!maybe_load_addr)
-          return false;
+          return resolve_err.ToError();
 
         addr_t load_addr = *maybe_load_addr;
 
@@ -1166,12 +1142,10 @@ bool DWARFExpression::Evaluate(
             stack.back().ClearContext();
             break;
           } else {
-            if (error_ptr)
-              error_ptr->SetErrorStringWithFormat(
-                  "Failed to dereference pointer for DW_OP_deref_size: "
-                  "%s\n",
-                  error.AsCString());
-            return false;
+            return llvm::createStringError(
+                "Failed to dereference pointer for DW_OP_deref_size: "
+                "%s\n",
+                error.AsCString());
           }
         }
         stack.back().GetScalar() = load_addr;
@@ -1195,30 +1169,25 @@ bool DWARFExpression::Evaluate(
                                              process->GetByteOrder(), size);
               stack.back().ClearContext();
             } else {
-              if (error_ptr)
-                error_ptr->SetErrorStringWithFormat(
-                    "Failed to dereference pointer from 0x%" PRIx64
-                    " for DW_OP_deref: %s\n",
-                    pointer_addr, error.AsCString());
-              return false;
+              return llvm::createStringError(
+                  "Failed to dereference pointer from 0x%" PRIx64
+                  " for DW_OP_deref: %s\n",
+                  pointer_addr, error.AsCString());
             }
           } else {
-            if (error_ptr)
-              error_ptr->SetErrorString("NULL process for DW_OP_deref_size.\n");
-            return false;
+
+            return llvm::createStringError(
+                "NULL process for DW_OP_deref_size.\n");
           }
         } else {
-          if (error_ptr)
-            error_ptr->SetErrorString(
-                "NULL execution context for DW_OP_deref_size.\n");
-          return false;
+          return llvm::createStringError(
+              "NULL execution context for DW_OP_deref_size.\n");
         }
         break;
 
       case Value::ValueType::Invalid:
-        if (error_ptr)
-          error_ptr->SetErrorString("Invalid value for DW_OP_deref_size.\n");
-        return false;
+
+        return llvm::createStringError("Invalid value for DW_OP_deref_size.\n");
       }
 
     } break;
@@ -1239,9 +1208,9 @@ bool DWARFExpression::Evaluate(
     // extended to the size of an address on the target machine before being
     // pushed on the expression stack.
     case DW_OP_xderef_size:
-      if (error_ptr)
-        error_ptr->SetErrorString("Unimplemented opcode: DW_OP_xderef_size.");
-      return false;
+
+      return llvm::createStringError(
+          "Unimplemented opcode: DW_OP_xderef_size.");
     // OPCODE: DW_OP_xderef
     // OPERANDS: none
     // DESCRIPTION: Provides an extended dereference mechanism. The entry at
@@ -1253,9 +1222,7 @@ bool DWARFExpression::Evaluate(
     // retrieved from the dereferenced address is the size of an address on the
     // target machine.
     case DW_OP_xderef:
-      if (error_ptr)
-        error_ptr->SetErrorString("Unimplemented opcode: DW_OP_xderef.");
-      return false;
+      return llvm::createStringError("Unimplemented opcode: DW_OP_xderef.");
 
     // All DW_OP_constXXX opcodes have a single operand as noted below:
     //
@@ -1308,9 +1275,7 @@ bool DWARFExpression::Evaluate(
     // DESCRIPTION: duplicates the value at the top of the stack
     case DW_OP_dup:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString("Expression stack empty for DW_OP_dup.");
-        return false;
+        return llvm::createStringError("Expression stack empty for DW_OP_dup.");
       } else
         stack.push_back(stack.back());
       break;
@@ -1320,9 +1285,8 @@ bool DWARFExpression::Evaluate(
     // DESCRIPTION: pops the value at the top of the stack
     case DW_OP_drop:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString("Expression stack empty for DW_OP_drop.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack empty for DW_OP_drop.");
       } else
         stack.pop_back();
       break;
@@ -1333,10 +1297,8 @@ bool DWARFExpression::Evaluate(
     // the top of the stack.
     case DW_OP_over:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_over.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_over.");
       } else
         stack.push_back(stack[stack.size() - 2]);
       break;
@@ -1350,10 +1312,8 @@ bool DWARFExpression::Evaluate(
       if (pick_idx < stack.size())
         stack.push_back(stack[stack.size() - 1 - pick_idx]);
       else {
-        if (error_ptr)
-          error_ptr->SetErrorStringWithFormat(
-              "Index %u out of range for DW_OP_pick.\n", pick_idx);
-        return false;
+        return llvm::createStringError(
+            "Index %u out of range for DW_OP_pick.\n", pick_idx);
       }
     } break;
 
@@ -1364,10 +1324,8 @@ bool DWARFExpression::Evaluate(
     // becomes the top of the stack
     case DW_OP_swap:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_swap.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_swap.");
       } else {
         tmp = stack.back();
         stack.back() = stack[stack.size() - 2];
@@ -1383,10 +1341,8 @@ bool DWARFExpression::Evaluate(
     // entry.
     case DW_OP_rot:
       if (stack.size() < 3) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 3 items for DW_OP_rot.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 3 items for DW_OP_rot.");
       } else {
         size_t last_idx = stack.size() - 1;
         Value old_top = stack[last_idx];
@@ -1403,15 +1359,11 @@ bool DWARFExpression::Evaluate(
     // represented, the result is undefined.
     case DW_OP_abs:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_abs.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_abs.");
       } else if (!stack.back().ResolveValue(exe_ctx).AbsoluteValue()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Failed to take the absolute value of the first stack item.");
-        return false;
+        return llvm::createStringError(
+            "Failed to take the absolute value of the first stack item.");
       }
       break;
 
@@ -1421,10 +1373,8 @@ bool DWARFExpression::Evaluate(
     // operation on the two, and pushes the result.
     case DW_OP_and:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_and.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_and.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1440,16 +1390,12 @@ bool DWARFExpression::Evaluate(
     // the result.
     case DW_OP_div:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_div.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_div.");
       } else {
         tmp = stack.back();
         if (tmp.ResolveValue(exe_ctx).IsZero()) {
-          if (error_ptr)
-            error_ptr->SetErrorString("Divide by zero.");
-          return false;
+          return llvm::createStringError("Divide by zero.");
         } else {
           stack.pop_back();
           Scalar divisor, dividend;
@@ -1459,9 +1405,7 @@ bool DWARFExpression::Evaluate(
           dividend.MakeSigned();
           stack.back() = dividend / divisor;
           if (!stack.back().ResolveValue(exe_ctx).IsValid()) {
-            if (error_ptr)
-              error_ptr->SetErrorString("Divide failed.");
-            return false;
+            return llvm::createStringError("Divide failed.");
           }
         }
       }
@@ -1473,10 +1417,8 @@ bool DWARFExpression::Evaluate(
     // of the stack from the former second entry, and pushes the result.
     case DW_OP_minus:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_minus.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_minus.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1492,10 +1434,8 @@ bool DWARFExpression::Evaluate(
     // stack.
     case DW_OP_mod:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_mod.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_mod.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1510,10 +1450,8 @@ bool DWARFExpression::Evaluate(
     // together, and pushes the result.
     case DW_OP_mul:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_mul.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_mul.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1527,16 +1465,11 @@ bool DWARFExpression::Evaluate(
     // DESCRIPTION: pops the top stack entry, and pushes its negation.
     case DW_OP_neg:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_neg.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_neg.");
       } else {
-        if (!stack.back().ResolveValue(exe_ctx).UnaryNegate()) {
-          if (error_ptr)
-            error_ptr->SetErrorString("Unary negate failed.");
-          return false;
-        }
+        if (!stack.back().ResolveValue(exe_ctx).UnaryNegate())
+          return llvm::createStringError("Unary negate failed.");
       }
       break;
 
@@ -1546,15 +1479,11 @@ bool DWARFExpression::Evaluate(
     // complement
     case DW_OP_not:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_not.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_not.");
       } else {
         if (!stack.back().ResolveValue(exe_ctx).OnesComplement()) {
-          if (error_ptr)
-            error_ptr->SetErrorString("Logical NOT failed.");
-          return false;
+          return llvm::createStringError("Logical NOT failed.");
         }
       }
       break;
@@ -1565,10 +1494,8 @@ bool DWARFExpression::Evaluate(
     // operation on the two, and pushes the result.
     case DW_OP_or:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_or.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_or.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1583,10 +1510,8 @@ bool DWARFExpression::Evaluate(
     // pushes the result.
     case DW_OP_plus:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_plus.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_plus.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1600,18 +1525,15 @@ bool DWARFExpression::Evaluate(
     // constant operand and pushes the result.
     case DW_OP_plus_uconst:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_plus_uconst.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_plus_uconst.");
       } else {
         const uint64_t uconst_value = opcodes.GetULEB128(&offset);
         // Implicit conversion from a UINT to a Scalar...
         stack.back().GetScalar() += uconst_value;
         if (!stack.back().GetScalar().IsValid()) {
-          if (error_ptr)
-            error_ptr->SetErrorString("DW_OP_plus_uconst failed.");
-          return false;
+
+          return llvm::createStringError("DW_OP_plus_uconst failed.");
         }
       }
       break;
@@ -1623,10 +1545,8 @@ bool DWARFExpression::Evaluate(
     // the stack, and pushes the result.
     case DW_OP_shl:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_shl.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_shl.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1641,18 +1561,14 @@ bool DWARFExpression::Evaluate(
     // specified by the former top of the stack, and pushes the result.
     case DW_OP_shr:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_shr.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_shr.");
       } else {
         tmp = stack.back();
         stack.pop_back();
         if (!stack.back().ResolveValue(exe_ctx).ShiftRightLogical(
                 tmp.ResolveValue(exe_ctx))) {
-          if (error_ptr)
-            error_ptr->SetErrorString("DW_OP_shr failed.");
-          return false;
+          return llvm::createStringError("DW_OP_shr failed.");
         }
       }
       break;
@@ -1665,10 +1581,8 @@ bool DWARFExpression::Evaluate(
     // of the stack, and pushes the result.
     case DW_OP_shra:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_shra.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_shra.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1682,10 +1596,8 @@ bool DWARFExpression::Evaluate(
     // exclusive-or operation on the two, and pushes the result.
     case DW_OP_xor:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_xor.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_xor.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1709,11 +1621,9 @@ bool DWARFExpression::Evaluate(
       if (new_offset <= opcodes.GetByteSize())
         offset = new_offset;
       else {
-        if (error_ptr)
-          error_ptr->SetErrorStringWithFormatv(
-              "Invalid opcode offset in DW_OP_skip: {0}+({1}) > {2}", offset,
-              skip_offset, opcodes.GetByteSize());
-        return false;
+        return llvm::createStringError(llvm::formatv(
+            "Invalid opcode offset in DW_OP_skip: {0}+({1}) > {2}", offset,
+            skip_offset, opcodes.GetByteSize()));
       }
     } break;
 
@@ -1726,10 +1636,8 @@ bool DWARFExpression::Evaluate(
     // the current operation, beginning after the 2-byte constant.
     case DW_OP_bra:
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_bra.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_bra.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1743,11 +1651,9 @@ bool DWARFExpression::Evaluate(
           if (new_offset <= opcodes.GetByteSize())
             offset = new_offset;
           else {
-            if (error_ptr)
-              error_ptr->SetErrorStringWithFormatv(
-                  "Invalid opcode offset in DW_OP_bra: {0}+({1}) > {2}", offset,
-                  bra_offset, opcodes.GetByteSize());
-            return false;
+            return llvm::createStringError(llvm::formatv(
+                "Invalid opcode offset in DW_OP_bra: {0}+({1}) > {2}", offset,
+                bra_offset, opcodes.GetByteSize()));
           }
         }
       }
@@ -1762,10 +1668,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_eq:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_eq.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_eq.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1783,10 +1687,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_ge:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_ge.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_ge.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1804,10 +1706,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_gt:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_gt.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_gt.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1825,10 +1725,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_le:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_le.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_le.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1846,10 +1744,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_lt:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_lt.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_lt.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1867,10 +1763,8 @@ bool DWARFExpression::Evaluate(
     // operation is false.
     case DW_OP_ne:
       if (stack.size() < 2) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 2 items for DW_OP_ne.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 2 items for DW_OP_ne.");
       } else {
         tmp = stack.back();
         stack.pop_back();
@@ -1957,10 +1851,11 @@ bool DWARFExpression::Evaluate(
       dwarf4_location_description_kind = Register;
       reg_num = op - DW_OP_reg0;
 
-      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, error_ptr, tmp))
+      Status read_err;
+      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, &read_err, tmp))
         stack.push_back(tmp);
       else
-        return false;
+        return read_err.ToError();
     } break;
     // OPCODE: DW_OP_regx
     // OPERANDS:
@@ -1969,10 +1864,11 @@ bool DWARFExpression::Evaluate(
     case DW_OP_regx: {
       dwarf4_location_description_kind = Register;
       reg_num = opcodes.GetULEB128(&offset);
-      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, error_ptr, tmp))
+      Status read_err;
+      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, &read_err, tmp))
         stack.push_back(tmp);
       else
-        return false;
+        return read_err.ToError();
     } break;
 
     // OPCODE: DW_OP_bregN
@@ -2014,7 +1910,8 @@ bool DWARFExpression::Evaluate(
     case DW_OP_breg31: {
       reg_num = op - DW_OP_breg0;
 
-      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, error_ptr,
+      Status read_err;
+      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, &read_err,
                                     tmp)) {
         int64_t breg_offset = opcodes.GetSLEB128(&offset);
         tmp.ResolveValue(exe_ctx) += (uint64_t)breg_offset;
@@ -2022,7 +1919,7 @@ bool DWARFExpression::Evaluate(
         stack.push_back(tmp);
         stack.back().SetValueType(Value::ValueType::LoadAddress);
       } else
-        return false;
+        return read_err.ToError();
     } break;
     // OPCODE: DW_OP_bregx
     // OPERANDS: 2
@@ -2033,7 +1930,8 @@ bool DWARFExpression::Evaluate(
     case DW_OP_bregx: {
       reg_num = opcodes.GetULEB128(&offset);
 
-      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, error_ptr,
+      Status read_err;
+      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, &read_err,
                                     tmp)) {
         int64_t breg_offset = opcodes.GetSLEB128(&offset);
         tmp.ResolveValue(exe_ctx) += (uint64_t)breg_offset;
@@ -2041,31 +1939,28 @@ bool DWARFExpression::Evaluate(
         stack.push_back(tmp);
         stack.back().SetValueType(Value::ValueType::LoadAddress);
       } else
-        return false;
+        return read_err.ToError();
     } break;
 
     case DW_OP_fbreg:
       if (exe_ctx) {
         if (frame) {
           Scalar value;
-          if (frame->GetFrameBaseValue(value, error_ptr)) {
+          Status fb_err;
+          if (frame->GetFrameBaseValue(value, &fb_err)) {
             int64_t fbreg_offset = opcodes.GetSLEB128(&offset);
             value += fbreg_offset;
             stack.push_back(value);
             stack.back().SetValueType(Value::ValueType::LoadAddress);
           } else
-            return false;
+            return fb_err.ToError();
         } else {
-          if (error_ptr)
-            error_ptr->SetErrorString(
-                "Invalid stack frame in context for DW_OP_fbreg opcode.");
-          return false;
+          return llvm::createStringError(
+              "Invalid stack frame in context for DW_OP_fbreg opcode.");
         }
       } else {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "NULL execution context for DW_OP_fbreg.\n");
-        return false;
+        return llvm::createStringError(
+            "NULL execution context for DW_OP_fbreg.\n");
       }
 
       break;
@@ -2127,7 +2022,7 @@ bool DWARFExpression::Evaluate(
           const lldb::addr_t addr = scalar.ULongLong(LLDB_INVALID_ADDRESS);
           switch (curr_piece_source_value_type) {
           case Value::ValueType::Invalid:
-            return false;
+            return llvm::createStringError("invalid value type");
           case Value::ValueType::LoadAddress:
           case Value::ValueType::FileAddress: {
             if (target) {
@@ -2136,35 +2031,28 @@ bool DWARFExpression::Evaluate(
                                        piece_byte_size, error,
                                        /*force_live_memory=*/false) !=
                     piece_byte_size) {
-                  if (error_ptr) {
-                    const char *addr_type = (curr_piece_source_value_type ==
-                                             Value::ValueType::LoadAddress)
-                                                ? "load"
-                                                : "file";
-                    error_ptr->SetErrorStringWithFormat(
-                        "failed to read memory DW_OP_piece(%" PRIu64
-                        ") from %s address 0x%" PRIx64,
-                        piece_byte_size, addr_type, addr);
-                  }
-                  return false;
+                  const char *addr_type = (curr_piece_source_value_type ==
+                                           Value::ValueType::LoadAddress)
+                                              ? "load"
+                                              : "file";
+                  return llvm::createStringError(
+                      "failed to read memory DW_OP_piece(%" PRIu64
+                      ") from %s address 0x%" PRIx64,
+                      piece_byte_size, addr_type, addr);
                 }
               } else {
-                if (error_ptr)
-                  error_ptr->SetErrorStringWithFormat(
-                      "failed to resize the piece memory buffer for "
-                      "DW_OP_piece(%" PRIu64 ")",
-                      piece_byte_size);
-                return false;
+                return llvm::createStringError(
+                    "failed to resize the piece memory buffer for "
+                    "DW_OP_piece(%" PRIu64 ")",
+                    piece_byte_size);
               }
             }
           } break;
           case Value::ValueType::HostAddress: {
-            if (error_ptr)
-              error_ptr->SetErrorStringWithFormat(
-                  "failed to read memory DW_OP_piece(%" PRIu64
-                  ") from host address 0x%" PRIx64,
-                  piece_byte_size, addr);
-            return false;
+            return llvm::createStringError(
+                "failed to read memory DW_OP_piece(%" PRIu64
+                ") from host address 0x%" PRIx64,
+                piece_byte_size, addr);
           } break;
 
           case Value::ValueType::Scalar: {
@@ -2172,14 +2060,11 @@ bool DWARFExpression::Evaluate(
             uint32_t bit_offset = 0;
             if (!scalar.ExtractBitfield(
                     bit_size, bit_offset)) {
-              if (error_ptr)
-                error_ptr->SetErrorStringWithFormat(
-                    "unable to extract %" PRIu64 " bytes from a %" PRIu64
-                    " byte scalar value.",
-                    piece_byte_size,
-                    (uint64_t)curr_piece_source_value.GetScalar()
-                        .GetByteSize());
-              return false;
+              return llvm::createStringError(
+                  "unable to extract %" PRIu64 " bytes from a %" PRIu64
+                  " byte scalar value.",
+                  piece_byte_size,
+                  (uint64_t)curr_piece_source_value.GetScalar().GetByteSize());
             }
             // Create curr_piece with bit_size. By default Scalar
             // grows to the nearest host integer type.
@@ -2198,27 +2083,20 @@ bool DWARFExpression::Evaluate(
             // so subsequent pieces will be able to access this piece and add
             // to it.
             if (pieces.AppendDataToHostBuffer(curr_piece) == 0) {
-              if (error_ptr)
-                error_ptr->SetErrorString("failed to append piece data");
-              return false;
+              return llvm::createStringError("failed to append piece data");
             }
           } else {
             // If this is the second or later piece there should be a value on
             // the stack.
             if (pieces.GetBuffer().GetByteSize() != op_piece_offset) {
-              if (error_ptr)
-                error_ptr->SetErrorStringWithFormat(
-                    "DW_OP_piece for offset %" PRIu64
-                    " but top of stack is of size %" PRIu64,
-                    op_piece_offset, pieces.GetBuffer().GetByteSize());
-              return false;
+              return llvm::createStringError(
+                  "DW_OP_piece for offset %" PRIu64
+                  " but top of stack is of size %" PRIu64,
+                  op_piece_offset, pieces.GetBuffer().GetByteSize());
             }
 
-            if (pieces.AppendDataToHostBuffer(curr_piece) == 0) {
-              if (error_ptr)
-                error_ptr->SetErrorString("failed to append piece data");
-              return false;
-            }
+            if (pieces.AppendDataToHostBuffer(curr_piece) == 0)
+              return llvm::createStringError("failed to append piece data");
           }
         }
         op_piece_offset += piece_byte_size;
@@ -2231,10 +2109,8 @@ bool DWARFExpression::Evaluate(
                                                LocationDescriptionKind::Empty);
         // Reset for the next piece.
         dwarf4_location_description_kind = Memory;
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_bit_piece.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_bit_piece.");
       } else {
         UpdateValueTypeFromLocationDescription(
             log, dwarf_cu, dwarf4_location_description_kind, &stack.back());
@@ -2244,30 +2120,26 @@ bool DWARFExpression::Evaluate(
         const uint64_t piece_bit_offset = opcodes.GetULEB128(&offset);
         switch (stack.back().GetValueType()) {
         case Value::ValueType::Invalid:
-          return false;
+          return llvm::createStringError(
+              "unable to extract bit value from invalid value.");
         case Value::ValueType::Scalar: {
           if (!stack.back().GetScalar().ExtractBitfield(piece_bit_size,
                                                         piece_bit_offset)) {
-            if (error_ptr)
-              error_ptr->SetErrorStringWithFormat(
-                  "unable to extract %" PRIu64 " bit value with %" PRIu64
-                  " bit offset from a %" PRIu64 " bit scalar value.",
-                  piece_bit_size, piece_bit_offset,
-                  (uint64_t)(stack.back().GetScalar().GetByteSize() * 8));
-            return false;
+            return llvm::createStringError(
+                "unable to extract %" PRIu64 " bit value with %" PRIu64
+                " bit offset from a %" PRIu64 " bit scalar value.",
+                piece_bit_size, piece_bit_offset,
+                (uint64_t)(stack.back().GetScalar().GetByteSize() * 8));
           }
         } break;
 
         case Value::ValueType::FileAddress:
         case Value::ValueType::LoadAddress:
         case Value::ValueType::HostAddress:
-          if (error_ptr) {
-            error_ptr->SetErrorStringWithFormat(
-                "unable to extract DW_OP_bit_piece(bit_size = %" PRIu64
-                ", bit_offset = %" PRIu64 ") from an address value.",
-                piece_bit_size, piece_bit_offset);
-          }
-          return false;
+          return llvm::createStringError(
+              "unable to extract DW_OP_bit_piece(bit_size = %" PRIu64
+              ", bit_offset = %" PRIu64 ") from an address value.",
+              piece_bit_size, piece_bit_offset);
         }
       }
       break;
@@ -2287,9 +2159,8 @@ bool DWARFExpression::Evaluate(
 
       if (!data) {
         LLDB_LOG(log, "Evaluate_DW_OP_implicit_value: could not be read data");
-        LLDB_ERRORF(error_ptr, "Could not evaluate %s.",
-                    DW_OP_value_to_name(op));
-        return false;
+        return llvm::createStringError("Could not evaluate %s.",
+                                       DW_OP_value_to_name(op));
       }
 
       Value result(data, len);
@@ -2299,8 +2170,8 @@ bool DWARFExpression::Evaluate(
 
     case DW_OP_implicit_pointer: {
       dwarf4_location_description_kind = Implicit;
-      LLDB_ERRORF(error_ptr, "Could not evaluate %s.", DW_OP_value_to_name(op));
-      return false;
+      return llvm::createStringError("Could not evaluate %s.",
+                                     DW_OP_value_to_name(op));
     }
 
     // OPCODE: DW_OP_push_object_address
@@ -2315,10 +2186,8 @@ bool DWARFExpression::Evaluate(
       if (object_address_ptr)
         stack.push_back(*object_address_ptr);
       else {
-        if (error_ptr)
-          error_ptr->SetErrorString("DW_OP_push_object_address used without "
-                                    "specifying an object address");
-        return false;
+        return llvm::createStringError("DW_OP_push_object_address used without "
+                                       "specifying an object address");
       }
       break;
 
@@ -2341,9 +2210,7 @@ bool DWARFExpression::Evaluate(
     // the stack by the called expression may be used as return values by prior
     // agreement between the calling and called expressions.
     case DW_OP_call2:
-      if (error_ptr)
-        error_ptr->SetErrorString("Unimplemented opcode DW_OP_call2.");
-      return false;
+      return llvm::createStringError("Unimplemented opcode DW_OP_call2.");
     // OPCODE: DW_OP_call4
     // OPERANDS: 1
     //      uint32_t compile unit relative offset of a DIE
@@ -2364,9 +2231,8 @@ bool DWARFExpression::Evaluate(
     // the stack by the called expression may be used as return values by prior
     // agreement between the calling and called expressions.
     case DW_OP_call4:
-      if (error_ptr)
-        error_ptr->SetErrorString("Unimplemented opcode DW_OP_call4.");
-      return false;
+
+      return llvm::createStringError("Unimplemented opcode DW_OP_call4.");
 
     // OPCODE: DW_OP_stack_value
     // OPERANDS: None
@@ -2376,10 +2242,8 @@ bool DWARFExpression::Evaluate(
     case DW_OP_stack_value:
       dwarf4_location_description_kind = Implicit;
       if (stack.empty()) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_stack_value.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_stack_value.");
       }
       stack.back().SetValueType(Value::ValueType::Scalar);
       break;
@@ -2393,10 +2257,8 @@ bool DWARFExpression::Evaluate(
     // different type, and push the result.
     case DW_OP_convert: {
       if (stack.size() < 1) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "Expression stack needs at least 1 item for DW_OP_convert.");
-        return false;
+        return llvm::createStringError(
+            "Expression stack needs at least 1 item for DW_OP_convert.");
       }
       const uint64_t die_offset = opcodes.GetULEB128(&offset);
       uint64_t bit_size;
@@ -2405,39 +2267,29 @@ bool DWARFExpression::Evaluate(
         // The generic type has the size of an address on the target
         // machine and an unspecified signedness. Scalar has no
         // "unspecified signedness", so we use unsigned types.
-        if (!module_sp) {
-          if (error_ptr)
-            error_ptr->SetErrorString("No module");
-          return false;
-        }
+        if (!module_sp)
+          return llvm::createStringError("No module");
         sign = false;
         bit_size = module_sp->GetArchitecture().GetAddressByteSize() * 8;
-        if (!bit_size) {
-          if (error_ptr)
-            error_ptr->SetErrorString("unspecified architecture");
-          return false;
-        }
+        if (!bit_size)
+          return llvm::createStringError("unspecified architecture");
       } else {
         // Retrieve the type DIE that the value is being converted to. This
         // offset is compile unit relative so we need to fix it up.
         const uint64_t abs_die_offset = die_offset +  dwarf_cu->GetOffset();
         // FIXME: the constness has annoying ripple effects.
         DWARFDIE die = const_cast<DWARFUnit *>(dwarf_cu)->GetDIE(abs_die_offset);
-        if (!die) {
-          if (error_ptr)
-            error_ptr->SetErrorString("Cannot resolve DW_OP_convert type DIE");
-          return false;
-        }
+        if (!die)
+          return llvm::createStringError(
+              "Cannot resolve DW_OP_convert type DIE");
         uint64_t encoding =
             die.GetAttributeValueAsUnsigned(DW_AT_encoding, DW_ATE_hi_user);
         bit_size = die.GetAttributeValueAsUnsigned(DW_AT_byte_size, 0) * 8;
         if (!bit_size)
           bit_size = die.GetAttributeValueAsUnsigned(DW_AT_bit_size, 0);
-        if (!bit_size) {
-          if (error_ptr)
-            error_ptr->SetErrorString("Unsupported type size in DW_OP_convert");
-          return false;
-        }
+        if (!bit_size)
+          return llvm::createStringError(
+              "Unsupported type size in DW_OP_convert");
         switch (encoding) {
         case DW_ATE_signed:
         case DW_ATE_signed_char:
@@ -2448,9 +2300,8 @@ bool DWARFExpression::Evaluate(
           sign = false;
           break;
         default:
-          if (error_ptr)
-            error_ptr->SetErrorString("Unsupported encoding in DW_OP_convert");
-          return false;
+          return llvm::createStringError(
+              "Unsupported encoding in DW_OP_convert");
         }
       }
       Scalar &top = stack.back().ResolveValue(exe_ctx);
@@ -2472,15 +2323,15 @@ bool DWARFExpression::Evaluate(
         if (cfa != LLDB_INVALID_ADDRESS) {
           stack.push_back(Scalar(cfa));
           stack.back().SetValueType(Value::ValueType::LoadAddress);
-        } else if (error_ptr)
-          error_ptr->SetErrorString("Stack frame does not include a canonical "
-                                    "frame address for DW_OP_call_frame_cfa "
-                                    "opcode.");
+        } else {
+          return llvm::createStringError(
+              "Stack frame does not include a canonical "
+              "frame address for DW_OP_call_frame_cfa "
+              "opcode.");
+        }
       } else {
-        if (error_ptr)
-          error_ptr->SetErrorString("Invalid stack frame in context for "
-                                    "DW_OP_call_frame_cfa opcode.");
-        return false;
+        return llvm::createStringError("Invalid stack frame in context for "
+                                       "DW_OP_call_frame_cfa opcode.");
       }
       break;
 
@@ -2493,29 +2344,20 @@ bool DWARFExpression::Evaluate(
     case DW_OP_form_tls_address:
     case DW_OP_GNU_push_tls_address: {
       if (stack.size() < 1) {
-        if (error_ptr) {
-          if (op == DW_OP_form_tls_address)
-            error_ptr->SetErrorString(
-                "DW_OP_form_tls_address needs an argument.");
-          else
-            error_ptr->SetErrorString(
-                "DW_OP_GNU_push_tls_address needs an argument.");
-        }
-        return false;
+        if (op == DW_OP_form_tls_address)
+          return llvm::createStringError(
+              "DW_OP_form_tls_address needs an argument.");
+        else
+          return llvm::createStringError(
+              "DW_OP_GNU_push_tls_address needs an argument.");
       }
 
-      if (!exe_ctx || !module_sp) {
-        if (error_ptr)
-          error_ptr->SetErrorString("No context to evaluate TLS within.");
-        return false;
-      }
+      if (!exe_ctx || !module_sp)
+        return llvm::createStringError("No context to evaluate TLS within.");
 
       Thread *thread = exe_ctx->GetThreadPtr();
-      if (!thread) {
-        if (error_ptr)
-          error_ptr->SetErrorString("No thread to evaluate TLS within.");
-        return false;
-      }
+      if (!thread)
+        return llvm::createStringError("No thread to evaluate TLS within.");
 
       // Lookup the TLS block address for this thread and module.
       const addr_t tls_file_addr =
@@ -2523,12 +2365,9 @@ bool DWARFExpression::Evaluate(
       const addr_t tls_load_addr =
           thread->GetThreadLocalData(module_sp, tls_file_addr);
 
-      if (tls_load_addr == LLDB_INVALID_ADDRESS) {
-        if (error_ptr)
-          error_ptr->SetErrorString(
-              "No TLS data currently exists for this thread.");
-        return false;
-      }
+      if (tls_load_addr == LLDB_INVALID_ADDRESS)
+        return llvm::createStringError(
+            "No TLS data currently exists for this thread.");
 
       stack.back().GetScalar() = tls_load_addr;
       stack.back().SetValueType(Value::ValueType::LoadAddress);
@@ -2542,12 +2381,9 @@ bool DWARFExpression::Evaluate(
     // and the 0 based index is the ULEB128 encoded index.
     case DW_OP_addrx:
     case DW_OP_GNU_addr_index: {
-      if (!dwarf_cu) {
-        if (error_ptr)
-          error_ptr->SetErrorString("DW_OP_GNU_addr_index found without a "
-                                    "compile unit being specified");
-        return false;
-      }
+      if (!dwarf_cu)
+        return llvm::createStringError("DW_OP_GNU_addr_index found without a "
+                                       "compile unit being specified");
       uint64_t index = opcodes.GetULEB128(&offset);
       lldb::addr_t value = dwarf_cu->ReadAddressFromDebugAddrSection(index);
       stack.push_back(Scalar(value));
@@ -2570,10 +2406,8 @@ bool DWARFExpression::Evaluate(
     // encoded index.
     case DW_OP_GNU_const_index: {
       if (!dwarf_cu) {
-        if (error_ptr)
-          error_ptr->SetErrorString("DW_OP_GNU_const_index found without a "
-                                    "compile unit being specified");
-        return false;
+        return llvm::createStringError("DW_OP_GNU_const_index found without a "
+                                       "compile unit being specified");
       }
       uint64_t index = opcodes.GetULEB128(&offset);
       lldb::addr_t value = dwarf_cu->ReadAddressFromDebugAddrSection(index);
@@ -2582,12 +2416,9 @@ bool DWARFExpression::Evaluate(
 
     case DW_OP_GNU_entry_value:
     case DW_OP_entry_value: {
-      if (!Evaluate_DW_OP_entry_value(stack, exe_ctx, reg_ctx, opcodes, offset,
-                                      error_ptr, log)) {
-        LLDB_ERRORF(error_ptr, "Could not evaluate %s.",
-                    DW_OP_value_to_name(op));
-        return false;
-      }
+      if (llvm::Error err = Evaluate_DW_OP_entry_value(stack, exe_ctx, reg_ctx,
+                                                       opcodes, offset, log))
+        return err;
       break;
     }
 
@@ -2598,23 +2429,18 @@ bool DWARFExpression::Evaluate(
           break;
         }
       }
-      if (error_ptr)
-        error_ptr->SetErrorStringWithFormatv(
-            "Unhandled opcode {0} in DWARFExpression", LocationAtom(op));
-      return false;
+      return llvm::createStringError(llvm::formatv(
+          "Unhandled opcode {0} in DWARFExpression", LocationAtom(op)));
     }
   }
 
   if (stack.empty()) {
     // Nothing on the stack, check if we created a piece value from DW_OP_piece
     // or DW_OP_bit_piece opcodes
-    if (pieces.GetBuffer().GetByteSize()) {
-      result = pieces;
-      return true;
-    }
-    if (error_ptr)
-      error_ptr->SetErrorString("Stack empty after evaluation.");
-    return false;
+    if (pieces.GetBuffer().GetByteSize())
+      return pieces;
+
+    return llvm::createStringError("Stack empty after evaluation.");
   }
 
   UpdateValueTypeFromLocationDescription(
@@ -2631,8 +2457,7 @@ bool DWARFExpression::Evaluate(
       LLDB_LOGF(log, "  %s", new_value.GetData());
     }
   }
-  result = stack.back();
-  return true; // Return true on success
+  return stack.back();
 }
 
 bool DWARFExpression::ParseDWARFLocationList(
diff --git a/lldb/source/Expression/DWARFExpressionList.cpp b/lldb/source/Expression/DWARFExpressionList.cpp
index cba4e4e5858ac..7a5cf9f9a0be4 100644
--- a/lldb/source/Expression/DWARFExpressionList.cpp
+++ b/lldb/source/Expression/DWARFExpressionList.cpp
@@ -198,12 +198,10 @@ void DWARFExpressionList::GetDescription(Stream *s,
   }
 }
 
-bool DWARFExpressionList::Evaluate(ExecutionContext *exe_ctx,
-                                   RegisterContext *reg_ctx,
-                                   lldb::addr_t func_load_addr,
-                                   const Value *initial_value_ptr,
-                                   const Value *object_address_ptr,
-                                   Value &result, Status *error_ptr) const {
+llvm::Expected<Value> DWARFExpressionList::Evaluate(
+    ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
+    lldb::addr_t func_load_addr, const Value *initial_value_ptr,
+    const Value *object_address_ptr) const {
   ModuleSP module_sp = m_module_wp.lock();
   DataExtractor data;
   RegisterKind reg_kind;
@@ -217,32 +215,26 @@ bool DWARFExpressionList::Evaluate(ExecutionContext *exe_ctx,
       if (exe_ctx)
         frame = exe_ctx->GetFramePtr();
       if (!frame)
-        return false;
+        return llvm::createStringError("no frame");
       RegisterContextSP reg_ctx_sp = frame->GetRegisterContext();
       if (!reg_ctx_sp)
-        return false;
+        return llvm::createStringError("no register context");
       reg_ctx_sp->GetPCForSymbolication(pc);
     }
 
     if (!pc.IsValid()) {
-      if (error_ptr)
-        error_ptr->SetErrorString("Invalid PC in frame.");
-      return false;
+      return llvm::createStringError("Invalid PC in frame.");
     }
     addr_t pc_load_addr = pc.GetLoadAddress(exe_ctx->GetTargetPtr());
     const DWARFExpression *entry =
         GetExpressionAtAddress(func_load_addr, pc_load_addr);
-    if (!entry) {
-      if (error_ptr) {
-        error_ptr->SetErrorString("variable not available");
-      }
-      return false;
-    }
+    if (!entry)
+      return llvm::createStringError("variable not available");
     expr = *entry;
   }
   expr.GetExpressionData(data);
   reg_kind = expr.GetRegisterKind();
   return DWARFExpression::Evaluate(exe_ctx, reg_ctx, module_sp, data,
                                    m_dwarf_cu, reg_kind, initial_value_ptr,
-                                   object_address_ptr, result, error_ptr);
+                                   object_address_ptr);
 }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index dc4cfc96b86f0..f0e1e0560aa9a 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -572,6 +572,8 @@ TypeSP DWARFASTParserClang::ParseTypeFromDWARF(const SymbolContext &sc,
 static std::optional<uint32_t>
 ExtractDataMemberLocation(DWARFDIE const &die, DWARFFormValue const &form_value,
                           ModuleSP module_sp) {
+  Log *log = GetLog(DWARFLog::TypeCompletion | DWARFLog::Lookups);
+
   // With DWARF 3 and later, if the value is an integer constant,
   // this form value is the offset in bytes from the beginning of
   // the containing entity.
@@ -579,21 +581,23 @@ ExtractDataMemberLocation(DWARFDIE const &die, DWARFFormValue const &form_value,
     return form_value.Unsigned();
 
   Value initialValue(0);
-  Value memberOffset(0);
   const DWARFDataExtractor &debug_info_data = die.GetData();
   uint32_t block_length = form_value.Unsigned();
   uint32_t block_offset =
       form_value.BlockData() - debug_info_data.GetDataStart();
-  if (!DWARFExpression::Evaluate(
-          nullptr, // ExecutionContext *
-          nullptr, // RegisterContext *
-          module_sp, DataExtractor(debug_info_data, block_offset, block_length),
-          die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr, memberOffset,
-          nullptr)) {
+
+  llvm::Expected<Value> memberOffset = DWARFExpression::Evaluate(
+      nullptr, // ExecutionContext *
+      nullptr, // RegisterContext *
+      module_sp, DataExtractor(debug_info_data, block_offset, block_length),
+      die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr);
+  if (!memberOffset) {
+    LLDB_LOG_ERROR(log, memberOffset.takeError(),
+                   "ExtractDataMemberLocation failed: {0}");
     return {};
   }
 
-  return memberOffset.ResolveValue(nullptr).UInt();
+  return memberOffset->ResolveValue(nullptr).UInt();
 }
 
 static TypePayloadClang GetPtrAuthMofidierPayload(const DWARFDIE &die) {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 661e4a78a0215..f4556925f5d68 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -2105,22 +2105,24 @@ SymbolFileDWARF::GlobalVariableMap &SymbolFileDWARF::GetGlobalAranges() {
               if (var_sp && !var_sp->GetLocationIsConstantValueData()) {
                 const DWARFExpressionList &location =
                     var_sp->LocationExpressionList();
-                Value location_result;
-                Status error;
                 ExecutionContext exe_ctx;
-                if (location.Evaluate(&exe_ctx, nullptr, LLDB_INVALID_ADDRESS,
-                                      nullptr, nullptr, location_result,
-                                      &error)) {
-                  if (location_result.GetValueType() ==
+                llvm::Expected<Value> location_result = location.Evaluate(
+                    &exe_ctx, nullptr, LLDB_INVALID_ADDRESS, nullptr, nullptr);
+                if (location_result) {
+                  if (location_result->GetValueType() ==
                       Value::ValueType::FileAddress) {
                     lldb::addr_t file_addr =
-                        location_result.GetScalar().ULongLong();
+                        location_result->GetScalar().ULongLong();
                     lldb::addr_t byte_size = 1;
                     if (var_sp->GetType())
                       byte_size =
                           var_sp->GetType()->GetByteSize(nullptr).value_or(0);
                     m_global_aranges_up->Append(GlobalVariableMap::Entry(
                         file_addr, byte_size, var_sp.get()));
+                  } else {
+                    LLDB_LOG_ERROR(
+                        GetLog(LLDBLog::Symbols), location_result.takeError(),
+                        "location expression failed to execute: {0}");
                   }
                 }
               }
diff --git a/lldb/source/Symbol/Function.cpp b/lldb/source/Symbol/Function.cpp
index 194f89bc51d80..96d8322b43d84 100644
--- a/lldb/source/Symbol/Function.cpp
+++ b/lldb/source/Symbol/Function.cpp
@@ -220,17 +220,18 @@ Function *IndirectCallEdge::GetCallee(ModuleList &images,
                                       ExecutionContext &exe_ctx) {
   Log *log = GetLog(LLDBLog::Step);
   Status error;
-  Value callee_addr_val;
-  if (!call_target.Evaluate(
-          &exe_ctx, exe_ctx.GetRegisterContext(), LLDB_INVALID_ADDRESS,
-          /*initial_value_ptr=*/nullptr,
-          /*object_address_ptr=*/nullptr, callee_addr_val, &error)) {
-    LLDB_LOGF(log, "IndirectCallEdge: Could not evaluate expression: %s",
-              error.AsCString());
+  llvm::Expected<Value> callee_addr_val = call_target.Evaluate(
+      &exe_ctx, exe_ctx.GetRegisterContext(), LLDB_INVALID_ADDRESS,
+      /*initial_value_ptr=*/nullptr,
+      /*object_address_ptr=*/nullptr);
+  if (!callee_addr_val) {
+    LLDB_LOG_ERROR(log, callee_addr_val.takeError(),
+                   "IndirectCallEdge: Could not evaluate expression: {0}");
     return nullptr;
   }
 
-  addr_t raw_addr = callee_addr_val.GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
+  addr_t raw_addr =
+      callee_addr_val->GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
   if (raw_addr == LLDB_INVALID_ADDRESS) {
     LLDB_LOG(log, "IndirectCallEdge: Could not extract address from scalar");
     return nullptr;
diff --git a/lldb/source/Target/RegisterContextUnwind.cpp b/lldb/source/Target/RegisterContextUnwind.cpp
index e2d712cb72eae..95e8abd763d53 100644
--- a/lldb/source/Target/RegisterContextUnwind.cpp
+++ b/lldb/source/Target/RegisterContextUnwind.cpp
@@ -1661,12 +1661,14 @@ RegisterContextUnwind::SavedLocationForRegister(
         unwindplan_registerkind);
     Value cfa_val = Scalar(m_cfa);
     cfa_val.SetValueType(Value::ValueType::LoadAddress);
-    Value result;
-    Status error;
-    if (dwarfexpr.Evaluate(&exe_ctx, this, 0, &cfa_val, nullptr, result,
-                           &error)) {
+    llvm::Expected<Value> result =
+        dwarfexpr.Evaluate(&exe_ctx, this, 0, &cfa_val, nullptr);
+    if (!result) {
+      LLDB_LOG_ERROR(log, result.takeError(),
+                     "DWARF expression failed to evaluate: {0}");
+    } else {
       addr_t val;
-      val = result.GetScalar().ULongLong();
+      val = result->GetScalar().ULongLong();
       if (unwindplan_regloc.IsDWARFExpression()) {
         regloc.type = UnwindLLDB::RegisterLocation::eRegisterValueInferred;
         regloc.location.inferred_value = val;
@@ -2029,11 +2031,10 @@ bool RegisterContextUnwind::ReadFrameAddress(
     DWARFExpressionList dwarfexpr(opcode_ctx, dwarfdata, nullptr);
     dwarfexpr.GetMutableExpressionAtAddress()->SetRegisterKind(
         row_register_kind);
-    Value result;
-    Status error;
-    if (dwarfexpr.Evaluate(&exe_ctx, this, 0, nullptr, nullptr, result,
-                           &error)) {
-      address = result.GetScalar().ULongLong();
+    llvm::Expected<Value> result =
+        dwarfexpr.Evaluate(&exe_ctx, this, 0, nullptr, nullptr);
+    if (result) {
+      address = result->GetScalar().ULongLong();
       if (ABISP abi_sp = m_thread.GetProcess()->GetABI())
         address = abi_sp->FixCodeAddress(address);
 
@@ -2042,7 +2043,7 @@ bool RegisterContextUnwind::ReadFrameAddress(
       return true;
     }
     UnwindLogMsg("Failed to set CFA value via DWARF expression: %s",
-                 error.AsCString());
+                 llvm::toString(result.takeError()).c_str());
     break;
   }
   case UnwindPlan::Row::FAValue::isRaSearch: {
diff --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
index 246871d5abaa5..3a2b4d05b2881 100644
--- a/lldb/source/Target/StackFrame.cpp
+++ b/lldb/source/Target/StackFrame.cpp
@@ -1091,24 +1091,19 @@ bool StackFrame::GetFrameBaseValue(Scalar &frame_base, Status *error_ptr) {
 
       m_flags.Set(GOT_FRAME_BASE);
       ExecutionContext exe_ctx(shared_from_this());
-      Value expr_value;
       addr_t loclist_base_addr = LLDB_INVALID_ADDRESS;
       if (!m_sc.function->GetFrameBaseExpression().IsAlwaysValidSingleExpr())
         loclist_base_addr =
             m_sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress(
                 exe_ctx.GetTargetPtr());
 
-      if (!m_sc.function->GetFrameBaseExpression().Evaluate(
-              &exe_ctx, nullptr, loclist_base_addr, nullptr, nullptr,
-              expr_value, &m_frame_base_error)) {
-        // We should really have an error if evaluate returns, but in case we
-        // don't, lets set the error to something at least.
-        if (m_frame_base_error.Success())
-          m_frame_base_error.SetErrorString(
-              "Evaluation of the frame base expression failed.");
-      } else {
-        m_frame_base = expr_value.ResolveValue(&exe_ctx);
-      }
+      llvm::Expected<Value> expr_value =
+          m_sc.function->GetFrameBaseExpression().Evaluate(
+              &exe_ctx, nullptr, loclist_base_addr, nullptr, nullptr);
+      if (!expr_value)
+        m_frame_base_error = expr_value.takeError();
+      else
+        m_frame_base = expr_value->ResolveValue(&exe_ctx);
     } else {
       m_frame_base_error.SetErrorString("No function in symbol context.");
     }
diff --git a/lldb/unittests/Expression/DWARFExpressionTest.cpp b/lldb/unittests/Expression/DWARFExpressionTest.cpp
index 602bd19ceecf8..f9e0605fce29d 100644
--- a/lldb/unittests/Expression/DWARFExpressionTest.cpp
+++ b/lldb/unittests/Expression/DWARFExpressionTest.cpp
@@ -33,23 +33,23 @@ static llvm::Expected<Scalar> Evaluate(llvm::ArrayRef<uint8_t> expr,
                                        ExecutionContext *exe_ctx = nullptr) {
   DataExtractor extractor(expr.data(), expr.size(), lldb::eByteOrderLittle,
                           /*addr_size*/ 4);
-  Value result;
-  Status status;
-  if (!DWARFExpression::Evaluate(exe_ctx, /*reg_ctx*/ nullptr, module_sp,
-                                 extractor, unit, lldb::eRegisterKindLLDB,
-                                 /*initial_value_ptr*/ nullptr,
-                                 /*object_address_ptr*/ nullptr, result,
-                                 &status))
-    return status.ToError();
-
-  switch (result.GetValueType()) {
+
+  llvm::Expected<Value> result =
+      DWARFExpression::Evaluate(exe_ctx, /*reg_ctx*/ nullptr, module_sp,
+                                extractor, unit, lldb::eRegisterKindLLDB,
+                                /*initial_value_ptr*/ nullptr,
+                                /*object_address_ptr*/ nullptr);
+  if (!result)
+    return result.takeError();
+
+  switch (result->GetValueType()) {
   case Value::ValueType::Scalar:
-    return result.GetScalar();
+    return result->GetScalar();
   case Value::ValueType::LoadAddress:
     return LLDB_INVALID_ADDRESS;
   case Value::ValueType::HostAddress: {
     // Convert small buffers to scalars to simplify the tests.
-    DataBufferHeap &buf = result.GetBuffer();
+    DataBufferHeap &buf = result->GetBuffer();
     if (buf.GetByteSize() <= 8) {
       uint64_t val = 0;
       memcpy(&val, buf.GetBytes(), buf.GetByteSize());
@@ -58,8 +58,9 @@ static llvm::Expected<Scalar> Evaluate(llvm::ArrayRef<uint8_t> expr,
   }
     [[fallthrough]];
   default:
-    return status.ToError();
+    break;
   }
+  return llvm::createStringError("unsupported value type");
 }
 
 class DWARFExpressionTester : public YAMLModuleTester {
@@ -454,16 +455,15 @@ TEST_F(DWARFExpressionMockProcessTest, WASM_DW_OP_addr) {
   uint8_t expr[] = {DW_OP_addr, 0x40, 0x0, 0x0, 0x0};
   DataExtractor extractor(expr, sizeof(expr), lldb::eByteOrderLittle,
                           /*addr_size*/ 4);
-  Value result;
-  Status status;
-  ASSERT_TRUE(DWARFExpression::Evaluate(
+
+  llvm::Expected<Value> result = DWARFExpression::Evaluate(
       &exe_ctx, /*reg_ctx*/ nullptr, /*module_sp*/ {}, extractor,
       /*unit*/ nullptr, lldb::eRegisterKindLLDB,
       /*initial_value_ptr*/ nullptr,
-      /*object_address_ptr*/ nullptr, result, &status))
-      << status.ToError();
+      /*object_address_ptr*/ nullptr);
 
-  ASSERT_EQ(result.GetValueType(), Value::ValueType::LoadAddress);
+  ASSERT_THAT_EXPECTED(result, llvm::Succeeded());
+  ASSERT_EQ(result->GetValueType(), Value::ValueType::LoadAddress);
 }
 
 TEST_F(DWARFExpressionMockProcessTest, WASM_DW_OP_addr_index) {
@@ -530,14 +530,14 @@ TEST_F(DWARFExpressionMockProcessTest, WASM_DW_OP_addr_index) {
 
   ExecutionContext exe_ctx(target_sp, false);
 
-  auto evaluate = [&](DWARFExpression &expr, Status &status, Value &result) {
+  auto evaluate = [&](DWARFExpression &expr) -> llvm::Expected<Value> {
     DataExtractor extractor;
     expr.GetExpressionData(extractor);
-    return DWARFExpression::Evaluate(
-        &exe_ctx, /*reg_ctx*/ nullptr, /*module_sp*/ {}, extractor, dwarf_cu,
-        lldb::eRegisterKindLLDB,
-        /*initial_value_ptr*/ nullptr,
-        /*object_address_ptr*/ nullptr, result, &status);
+    return DWARFExpression::Evaluate(&exe_ctx, /*reg_ctx*/ nullptr,
+                                     /*module_sp*/ {}, extractor, dwarf_cu,
+                                     lldb::eRegisterKindLLDB,
+                                     /*initial_value_ptr*/ nullptr,
+                                     /*object_address_ptr*/ nullptr);
   };
 
   // DW_OP_addrx takes a single leb128 operand, the index in the addr table:
@@ -546,16 +546,16 @@ TEST_F(DWARFExpressionMockProcessTest, WASM_DW_OP_addr_index) {
                           /*addr_size*/ 4);
   DWARFExpression expr(extractor);
 
-  Status status;
-  Value result;
-  ASSERT_TRUE(evaluate(expr, status, result)) << status.ToError();
-  ASSERT_EQ(result.GetValueType(), Value::ValueType::LoadAddress);
-  ASSERT_EQ(result.GetScalar().UInt(), 0x5678u);
+  llvm::Expected<Value> result = evaluate(expr);
+  ASSERT_THAT_EXPECTED(result, llvm::Succeeded());
+  ASSERT_EQ(result->GetValueType(), Value::ValueType::LoadAddress);
+  ASSERT_EQ(result->GetScalar().UInt(), 0x5678u);
 
   ASSERT_TRUE(expr.Update_DW_OP_addr(dwarf_cu, 0xdeadbeef));
-  ASSERT_TRUE(evaluate(expr, status, result)) << status.ToError();
-  ASSERT_EQ(result.GetValueType(), Value::ValueType::LoadAddress);
-  ASSERT_EQ(result.GetScalar().UInt(), 0xdeadbeefu);
+  result = evaluate(expr);
+  ASSERT_THAT_EXPECTED(result, llvm::Succeeded());
+  ASSERT_EQ(result->GetValueType(), Value::ValueType::LoadAddress);
+  ASSERT_EQ(result->GetScalar().UInt(), 0xdeadbeefu);
 }
 
 class CustomSymbolFileDWARF : public SymbolFileDWARF {
@@ -825,15 +825,13 @@ TEST_F(DWARFExpressionMockProcessTest, DW_OP_piece_file_addr) {
                     DW_OP_addr, 0x50, 0x0, 0x0, 0x0, DW_OP_piece, 1};
   DataExtractor extractor(expr, sizeof(expr), lldb::eByteOrderLittle,
                           /*addr_size*/ 4);
-  Value result;
-  Status status;
-  ASSERT_TRUE(DWARFExpression::Evaluate(
+  llvm::Expected<Value> result = DWARFExpression::Evaluate(
       &exe_ctx, /*reg_ctx*/ nullptr, /*module_sp*/ {}, extractor,
       /*unit*/ nullptr, lldb::eRegisterKindLLDB,
       /*initial_value_ptr*/ nullptr,
-      /*object_address_ptr*/ nullptr, result, &status))
-      << status.ToError();
+      /*object_address_ptr*/ nullptr);
 
-  ASSERT_EQ(result.GetValueType(), Value::ValueType::HostAddress);
-  ASSERT_THAT(result.GetBuffer().GetData(), ElementsAre(0x11, 0x22));
+  ASSERT_THAT_EXPECTED(result, llvm::Succeeded());
+  ASSERT_EQ(result->GetValueType(), Value::ValueType::HostAddress);
+  ASSERT_THAT(result->GetBuffer().GetData(), ElementsAre(0x11, 0x22));
 }

>From b6e28ab5747c277429fb17dafc331bd87d34569b Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Tue, 4 Jun 2024 19:28:40 -0700
Subject: [PATCH 3/5] [lldb] Move LLDB_LOG_ERROR to correct else block

---
 lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index f4556925f5d68..af3ba2cd5b39d 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -2119,11 +2119,11 @@ SymbolFileDWARF::GlobalVariableMap &SymbolFileDWARF::GetGlobalAranges() {
                           var_sp->GetType()->GetByteSize(nullptr).value_or(0);
                     m_global_aranges_up->Append(GlobalVariableMap::Entry(
                         file_addr, byte_size, var_sp.get()));
-                  } else {
-                    LLDB_LOG_ERROR(
-                        GetLog(LLDBLog::Symbols), location_result.takeError(),
-                        "location expression failed to execute: {0}");
                   }
+                } else {
+                  LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols),
+                                 location_result.takeError(),
+                                 "location expression failed to execute: {0}");
                 }
               }
             }

>From aa51bea351e0fdcf1626ca545fa8c4523d9b5f8a Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Tue, 4 Jun 2024 19:48:26 -0700
Subject: [PATCH 4/5] [lldb] Improve DW_OP_entry_value error reporting

---
 lldb/source/Expression/DWARFExpression.cpp    | 44 +++++++------------
 .../basic_entry_values/main.cpp               |  7 +--
 2 files changed, 21 insertions(+), 30 deletions(-)

diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 5c7ab49410efe..80d03c84fadbd 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -593,15 +593,13 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
 
   // 1. Find the function which pushed the current frame onto the stack.
   if ((!exe_ctx || !exe_ctx->HasTargetScope()) || !reg_ctx) {
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no exe/reg context");
+    return llvm::createStringError("no exe/reg context");
   }
 
   StackFrame *current_frame = exe_ctx->GetFramePtr();
   Thread *thread = exe_ctx->GetThreadPtr();
   if (!current_frame || !thread)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no current frame/thread");
+    return llvm::createStringError("no current frame/thread");
 
   Target &target = exe_ctx->GetTargetRef();
   StackFrameSP parent_frame = nullptr;
@@ -619,9 +617,7 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     // parent frame.
     if (return_pc == LLDB_INVALID_ADDRESS) {
       return_pc = parent_frame->GetFrameCodeAddress().GetLoadAddress(&target);
-      LLDB_LOG(log,
-               "Evaluate_DW_OP_entry_value: immediate ancestor with pc = {0:x}",
-               return_pc);
+      LLDB_LOG(log, "immediate ancestor with pc = {0:x}", return_pc);
     }
 
     // If we've found an inlined frame, skip it (these have no call site
@@ -633,23 +629,20 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     break;
   }
   if (!parent_frame || !parent_frame->GetRegisterContext()) {
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no parent frame with reg ctx");
+    return llvm::createStringError("no parent frame with reg ctx");
   }
 
   Function *parent_func =
       parent_frame->GetSymbolContext(eSymbolContextFunction).function;
   if (!parent_func)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no parent function");
+    return llvm::createStringError("no parent function");
 
   // 2. Find the call edge in the parent function responsible for creating the
   //    current activation.
   Function *current_func =
       current_frame->GetSymbolContext(eSymbolContextFunction).function;
   if (!current_func)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no current function");
+    return llvm::createStringError("no current function");
 
   CallEdge *call_edge = nullptr;
   ModuleList &modlist = target.GetImages();
@@ -660,16 +653,14 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     // produced by an ambiguous tail call. In this case, refuse to proceed.
     call_edge = parent_func->GetCallEdgeForReturnAddress(return_pc, target);
     if (!call_edge) {
-      return llvm::createStringError(llvm::formatv(
-          "Evaluate_DW_OP_entry_value: no call edge for retn-pc = {0:x} "
-          "in parent frame {1}",
-          return_pc, parent_func->GetName()));
+      return llvm::createStringError(
+          llvm::formatv("no call edge for retn-pc = {0:x} in parent frame {1}",
+                        return_pc, parent_func->GetName()));
     }
     Function *callee_func = call_edge->GetCallee(modlist, parent_exe_ctx);
     if (callee_func != current_func) {
       return llvm::createStringError(
-          "Evaluate_DW_OP_entry_value: ambiguous call sequence, "
-          "can't find real parent frame");
+          "ambiguous call sequence, can't find real parent frame");
     }
   } else {
     // The StackFrameList solver machinery has deduced that an unambiguous tail
@@ -683,9 +674,8 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     }
   }
   if (!call_edge)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no unambiguous edge from parent "
-        "to current function");
+    return llvm::createStringError("no unambiguous edge from parent "
+                                   "to current function");
 
   // 3. Attempt to locate the DW_OP_entry_value expression in the set of
   //    available call site parameters. If found, evaluate the corresponding
@@ -693,8 +683,7 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
   const uint32_t subexpr_len = opcodes.GetULEB128(&opcode_offset);
   const void *subexpr_data = opcodes.GetData(&opcode_offset, subexpr_len);
   if (!subexpr_data)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: subexpr could not be read");
+    return llvm::createStringError("subexpr could not be read");
 
   const CallSiteParameter *matched_param = nullptr;
   for (const CallSiteParameter &param : call_edge->GetCallSiteParameters()) {
@@ -721,8 +710,7 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack,
     }
   }
   if (!matched_param)
-    return llvm::createStringError(
-        "Evaluate_DW_OP_entry_value: no matching call site param found");
+    return llvm::createStringError("no matching call site param found");
 
   // TODO: Add support for DW_OP_push_object_address within a DW_OP_entry_value
   // subexpresion whenever llvm does.
@@ -2418,7 +2406,9 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
     case DW_OP_entry_value: {
       if (llvm::Error err = Evaluate_DW_OP_entry_value(stack, exe_ctx, reg_ctx,
                                                        opcodes, offset, log))
-        return err;
+        return llvm::createStringError(
+            "could not evaluate DW_OP_entry_value: %s",
+            llvm::toString(std::move(err)).c_str());
       break;
     }
 
diff --git a/lldb/test/API/functionalities/param_entry_vals/basic_entry_values/main.cpp b/lldb/test/API/functionalities/param_entry_vals/basic_entry_values/main.cpp
index 91769e8768017..2b28d0357e0cc 100644
--- a/lldb/test/API/functionalities/param_entry_vals/basic_entry_values/main.cpp
+++ b/lldb/test/API/functionalities/param_entry_vals/basic_entry_values/main.cpp
@@ -52,9 +52,10 @@ __attribute__((noinline)) void func4_amb(int &sink, int x) {
   //%     expect_cmd_failure=True)
   //% self.filecheck("expr sink", "main.cpp","-check-prefix=FUNC4-EXPR",
   //%     expect_cmd_failure=True)
-  // FUNC4-EXPR-FAIL: couldn't get the value of variable x: Could not evaluate
-  // DW_OP_entry_value. FUNC4-EXPR: couldn't get the value of variable sink:
-  // Could not evaluate DW_OP_entry_value.
+  // FUNC4-EXPR-FAIL: couldn't get the value of variable x: could not evaluate
+  // DW_OP_entry_value: no matching call site param found FUNC4-EXPR: couldn't
+  // get the value of variable sink: could not evaluate DW_OP_entry_value: no
+  // matching call site param found
 }
 
 __attribute__((noinline)) void func5_amb() {}

>From 9b69aeec6207dac23c402d4dc074056883d1f16e Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Wed, 5 Jun 2024 09:30:47 -0700
Subject: [PATCH 5/5] Use inline comments

---
 .../Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp      | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index f0e1e0560aa9a..7d7e835c3d732 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -587,10 +587,10 @@ ExtractDataMemberLocation(DWARFDIE const &die, DWARFFormValue const &form_value,
       form_value.BlockData() - debug_info_data.GetDataStart();
 
   llvm::Expected<Value> memberOffset = DWARFExpression::Evaluate(
-      nullptr, // ExecutionContext *
-      nullptr, // RegisterContext *
-      module_sp, DataExtractor(debug_info_data, block_offset, block_length),
-      die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr);
+      /*ExecutionContext=*/nullptr,
+      /*RegisterContext=*/nullptr, module_sp,
+      DataExtractor(debug_info_data, block_offset, block_length), die.GetCU(),
+      eRegisterKindDWARF, &initialValue, nullptr);
   if (!memberOffset) {
     LLDB_LOG_ERROR(log, memberOffset.takeError(),
                    "ExtractDataMemberLocation failed: {0}");



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