lldb/source/Target/StackFrame.cpp

//===-- StackFrame.cpp ------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "lldb/Target/StackFrame.h"
#include "lldb/Core/Debugger.h"
#include "lldb/Core/Disassembler.h"
#include "lldb/Core/FormatEntity.h"
#include "lldb/Core/Mangled.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/Value.h"
#include "lldb/Core/ValueObjectConstResult.h"
#include "lldb/Core/ValueObjectMemory.h"
#include "lldb/Core/ValueObjectVariable.h"
#include "lldb/Symbol/CompileUnit.h"
#include "lldb/Symbol/Function.h"
#include "lldb/Symbol/Symbol.h"
#include "lldb/Symbol/SymbolContextScope.h"
#include "lldb/Symbol/Type.h"
#include "lldb/Symbol/VariableList.h"
#include "lldb/Target/ABI.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/StackFrameRecognizer.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Thread.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/RegisterValue.h"

#include "lldb/lldb-enumerations.h"

#include <memory>

using namespace lldb;
using namespace lldb_private;

// The first bits in the flags are reserved for the SymbolContext::Scope bits
// so we know if we have tried to look up information in our internal symbol
// context (m_sc) already.
#define RESOLVED_FRAME_CODE_ADDR (uint32_t(eSymbolContextEverything + 1))
#define RESOLVED_FRAME_ID_SYMBOL_SCOPE (RESOLVED_FRAME_CODE_ADDR << 1)
#define GOT_FRAME_BASE (RESOLVED_FRAME_ID_SYMBOL_SCOPE << 1)
#define RESOLVED_VARIABLES (GOT_FRAME_BASE << 1)
#define RESOLVED_GLOBAL_VARIABLES (RESOLVED_VARIABLES << 1)

StackFrame::StackFrame(const ThreadSP &thread_sp, user_id_t frame_idx,
                       user_id_t unwind_frame_index, addr_t cfa,
                       bool cfa_is_valid, addr_t pc, StackFrame::Kind kind,
                       bool behaves_like_zeroth_frame,
                       const SymbolContext *sc_ptr)
    : m_thread_wp(thread_sp), m_frame_index(frame_idx),
      m_concrete_frame_index(unwind_frame_index), m_reg_context_sp(),
      m_id(pc, cfa, nullptr), m_frame_code_addr(pc), m_sc(), m_flags(),
      m_frame_base(), m_frame_base_error(), m_cfa_is_valid(cfa_is_valid),
      m_stack_frame_kind(kind),
      m_behaves_like_zeroth_frame(behaves_like_zeroth_frame),
      m_variable_list_sp(), m_variable_list_value_objects(),
      m_recognized_frame_sp(), m_disassembly(), m_mutex() {
  // If we don't have a CFA value, use the frame index for our StackID so that
  // recursive functions properly aren't confused with one another on a history
  // stack.
  if (IsHistorical() && !m_cfa_is_valid) {
    m_id.SetCFA(m_frame_index);
  }

  if (sc_ptr != nullptr) {
    m_sc = *sc_ptr;
    m_flags.Set(m_sc.GetResolvedMask());
  }
}

StackFrame::StackFrame(const ThreadSP &thread_sp, user_id_t frame_idx,
                       user_id_t unwind_frame_index,
                       const RegisterContextSP &reg_context_sp, addr_t cfa,
                       addr_t pc, bool behaves_like_zeroth_frame,
                       const SymbolContext *sc_ptr)
    : m_thread_wp(thread_sp), m_frame_index(frame_idx),
      m_concrete_frame_index(unwind_frame_index),
      m_reg_context_sp(reg_context_sp), m_id(pc, cfa, nullptr),
      m_frame_code_addr(pc), m_sc(), m_flags(), m_frame_base(),
      m_frame_base_error(), m_cfa_is_valid(true),
      m_stack_frame_kind(StackFrame::Kind::Regular),
      m_behaves_like_zeroth_frame(behaves_like_zeroth_frame),
      m_variable_list_sp(), m_variable_list_value_objects(),
      m_recognized_frame_sp(), m_disassembly(), m_mutex() {
  if (sc_ptr != nullptr) {
    m_sc = *sc_ptr;
    m_flags.Set(m_sc.GetResolvedMask());
  }

  if (reg_context_sp && !m_sc.target_sp) {
    m_sc.target_sp = reg_context_sp->CalculateTarget();
    if (m_sc.target_sp)
      m_flags.Set(eSymbolContextTarget);
  }
}

StackFrame::StackFrame(const ThreadSP &thread_sp, user_id_t frame_idx,
                       user_id_t unwind_frame_index,
                       const RegisterContextSP &reg_context_sp, addr_t cfa,
                       const Address &pc_addr, bool behaves_like_zeroth_frame,
                       const SymbolContext *sc_ptr)
    : m_thread_wp(thread_sp), m_frame_index(frame_idx),
      m_concrete_frame_index(unwind_frame_index),
      m_reg_context_sp(reg_context_sp),
      m_id(pc_addr.GetLoadAddress(thread_sp->CalculateTarget().get()), cfa,
           nullptr),
      m_frame_code_addr(pc_addr), m_sc(), m_flags(), m_frame_base(),
      m_frame_base_error(), m_cfa_is_valid(true),
      m_stack_frame_kind(StackFrame::Kind::Regular),
      m_behaves_like_zeroth_frame(behaves_like_zeroth_frame),
      m_variable_list_sp(), m_variable_list_value_objects(),
      m_recognized_frame_sp(), m_disassembly(), m_mutex() {
  if (sc_ptr != nullptr) {
    m_sc = *sc_ptr;
    m_flags.Set(m_sc.GetResolvedMask());
  }

  if (!m_sc.target_sp && reg_context_sp) {
    m_sc.target_sp = reg_context_sp->CalculateTarget();
    if (m_sc.target_sp)
      m_flags.Set(eSymbolContextTarget);
  }

  ModuleSP pc_module_sp(pc_addr.GetModule());
  if (!m_sc.module_sp || m_sc.module_sp != pc_module_sp) {
    if (pc_module_sp) {
      m_sc.module_sp = pc_module_sp;
      m_flags.Set(eSymbolContextModule);
    } else {
      m_sc.module_sp.reset();
    }
  }
}

StackFrame::~StackFrame() = default;

StackID &StackFrame::GetStackID() {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  // Make sure we have resolved the StackID object's symbol context scope if we
  // already haven't looked it up.

  if (m_flags.IsClear(RESOLVED_FRAME_ID_SYMBOL_SCOPE)) {
    if (m_id.GetSymbolContextScope()) {
      // We already have a symbol context scope, we just don't have our flag
      // bit set.
      m_flags.Set(RESOLVED_FRAME_ID_SYMBOL_SCOPE);
    } else {
      // Calculate the frame block and use this for the stack ID symbol context
      // scope if we have one.
      SymbolContextScope *scope = GetFrameBlock();
      if (scope == nullptr) {
        // We don't have a block, so use the symbol
        if (m_flags.IsClear(eSymbolContextSymbol))
          GetSymbolContext(eSymbolContextSymbol);

        // It is ok if m_sc.symbol is nullptr here
        scope = m_sc.symbol;
      }
      // Set the symbol context scope (the accessor will set the
      // RESOLVED_FRAME_ID_SYMBOL_SCOPE bit in m_flags).
      SetSymbolContextScope(scope);
    }
  }
  return m_id;
}

uint32_t StackFrame::GetFrameIndex() const {
  ThreadSP thread_sp = GetThread();
  if (thread_sp)
    return thread_sp->GetStackFrameList()->GetVisibleStackFrameIndex(
        m_frame_index);
  else
    return m_frame_index;
}

void StackFrame::SetSymbolContextScope(SymbolContextScope *symbol_scope) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  m_flags.Set(RESOLVED_FRAME_ID_SYMBOL_SCOPE);
  m_id.SetSymbolContextScope(symbol_scope);
}

const Address &StackFrame::GetFrameCodeAddress() {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (m_flags.IsClear(RESOLVED_FRAME_CODE_ADDR) &&
      !m_frame_code_addr.IsSectionOffset()) {
    m_flags.Set(RESOLVED_FRAME_CODE_ADDR);

    // Resolve the PC into a temporary address because if ResolveLoadAddress
    // fails to resolve the address, it will clear the address object...
    ThreadSP thread_sp(GetThread());
    if (thread_sp) {
      TargetSP target_sp(thread_sp->CalculateTarget());
      if (target_sp) {
        const bool allow_section_end = true;
        if (m_frame_code_addr.SetOpcodeLoadAddress(
                m_frame_code_addr.GetOffset(), target_sp.get(),
                AddressClass::eCode, allow_section_end)) {
          ModuleSP module_sp(m_frame_code_addr.GetModule());
          if (module_sp) {
            m_sc.module_sp = module_sp;
            m_flags.Set(eSymbolContextModule);
          }
        }
      }
    }
  }
  return m_frame_code_addr;
}

bool StackFrame::ChangePC(addr_t pc) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  // We can't change the pc value of a history stack frame - it is immutable.
  if (IsHistorical())
    return false;
  m_frame_code_addr.SetRawAddress(pc);
  m_sc.Clear(false);
  m_flags.Reset(0);
  ThreadSP thread_sp(GetThread());
  if (thread_sp)
    thread_sp->ClearStackFrames();
  return true;
}

const char *StackFrame::Disassemble() {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (m_disassembly.Empty()) {
    ExecutionContext exe_ctx(shared_from_this());
    Target *target = exe_ctx.GetTargetPtr();
    if (target) {
      const char *plugin_name = nullptr;
      const char *flavor = nullptr;
      Disassembler::Disassemble(target->GetDebugger(),
                                target->GetArchitecture(), plugin_name, flavor,
                                exe_ctx, 0, false, 0, 0, m_disassembly);
    }
    if (m_disassembly.Empty())
      return nullptr;
  }

  return m_disassembly.GetData();
}

Block *StackFrame::GetFrameBlock() {
  if (m_sc.block == nullptr && m_flags.IsClear(eSymbolContextBlock))
    GetSymbolContext(eSymbolContextBlock);

  if (m_sc.block) {
    Block *inline_block = m_sc.block->GetContainingInlinedBlock();
    if (inline_block) {
      // Use the block with the inlined function info as the frame block we
      // want this frame to have only the variables for the inlined function
      // and its non-inlined block child blocks.
      return inline_block;
    } else {
      // This block is not contained within any inlined function blocks with so
      // we want to use the top most function block.
      return &m_sc.function->GetBlock(false);
    }
  }
  return nullptr;
}

// Get the symbol context if we already haven't done so by resolving the
// PC address as much as possible. This way when we pass around a
// StackFrame object, everyone will have as much information as possible and no
// one will ever have to look things up manually.
const SymbolContext &
StackFrame::GetSymbolContext(SymbolContextItem resolve_scope) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  // Copy our internal symbol context into "sc".
  if ((m_flags.Get() & resolve_scope) != resolve_scope) {
    uint32_t resolved = 0;

    // If the target was requested add that:
    if (!m_sc.target_sp) {
      m_sc.target_sp = CalculateTarget();
      if (m_sc.target_sp)
        resolved |= eSymbolContextTarget;
    }

    // Resolve our PC to section offset if we haven't already done so and if we
    // don't have a module. The resolved address section will contain the
    // module to which it belongs
    if (!m_sc.module_sp && m_flags.IsClear(RESOLVED_FRAME_CODE_ADDR))
      GetFrameCodeAddress();

    // If this is not frame zero, then we need to subtract 1 from the PC value
    // when doing address lookups since the PC will be on the instruction
    // following the function call instruction...

    Address lookup_addr(GetFrameCodeAddress());
    if (!m_behaves_like_zeroth_frame && lookup_addr.IsValid()) {
      addr_t offset = lookup_addr.GetOffset();
      if (offset > 0) {
        lookup_addr.SetOffset(offset - 1);

      } else {
        // lookup_addr is the start of a section.  We need do the math on the
        // actual load address and re-compute the section.  We're working with
        // a 'noreturn' function at the end of a section.
        ThreadSP thread_sp(GetThread());
        if (thread_sp) {
          TargetSP target_sp(thread_sp->CalculateTarget());
          if (target_sp) {
            addr_t addr_minus_one =
                lookup_addr.GetLoadAddress(target_sp.get()) - 1;
            lookup_addr.SetLoadAddress(addr_minus_one, target_sp.get());
          } else {
            lookup_addr.SetOffset(offset - 1);
          }
        }
      }
    }

    if (m_sc.module_sp) {
      // We have something in our stack frame symbol context, lets check if we
      // haven't already tried to lookup one of those things. If we haven't
      // then we will do the query.

      SymbolContextItem actual_resolve_scope = SymbolContextItem(0);

      if (resolve_scope & eSymbolContextCompUnit) {
        if (m_flags.IsClear(eSymbolContextCompUnit)) {
          if (m_sc.comp_unit)
            resolved |= eSymbolContextCompUnit;
          else
            actual_resolve_scope |= eSymbolContextCompUnit;
        }
      }

      if (resolve_scope & eSymbolContextFunction) {
        if (m_flags.IsClear(eSymbolContextFunction)) {
          if (m_sc.function)
            resolved |= eSymbolContextFunction;
          else
            actual_resolve_scope |= eSymbolContextFunction;
        }
      }

      if (resolve_scope & eSymbolContextBlock) {
        if (m_flags.IsClear(eSymbolContextBlock)) {
          if (m_sc.block)
            resolved |= eSymbolContextBlock;
          else
            actual_resolve_scope |= eSymbolContextBlock;
        }
      }

      if (resolve_scope & eSymbolContextSymbol) {
        if (m_flags.IsClear(eSymbolContextSymbol)) {
          if (m_sc.symbol)
            resolved |= eSymbolContextSymbol;
          else
            actual_resolve_scope |= eSymbolContextSymbol;
        }
      }

      if (resolve_scope & eSymbolContextLineEntry) {
        if (m_flags.IsClear(eSymbolContextLineEntry)) {
          if (m_sc.line_entry.IsValid())
            resolved |= eSymbolContextLineEntry;
          else
            actual_resolve_scope |= eSymbolContextLineEntry;
        }
      }

      if (actual_resolve_scope) {
        // We might be resolving less information than what is already in our
        // current symbol context so resolve into a temporary symbol context
        // "sc" so we don't clear out data we have already found in "m_sc"
        SymbolContext sc;
        // Set flags that indicate what we have tried to resolve
        resolved |= m_sc.module_sp->ResolveSymbolContextForAddress(
            lookup_addr, actual_resolve_scope, sc);
        // Only replace what we didn't already have as we may have information
        // for an inlined function scope that won't match what a standard
        // lookup by address would match
        if ((resolved & eSymbolContextCompUnit) && m_sc.comp_unit == nullptr)
          m_sc.comp_unit = sc.comp_unit;
        if ((resolved & eSymbolContextFunction) && m_sc.function == nullptr)
          m_sc.function = sc.function;
        if ((resolved & eSymbolContextBlock) && m_sc.block == nullptr)
          m_sc.block = sc.block;
        if ((resolved & eSymbolContextSymbol) && m_sc.symbol == nullptr)
          m_sc.symbol = sc.symbol;
        if ((resolved & eSymbolContextLineEntry) &&
            !m_sc.line_entry.IsValid()) {
          m_sc.line_entry = sc.line_entry;
          m_sc.line_entry.ApplyFileMappings(m_sc.target_sp);
        }
      }
    } else {
      // If we don't have a module, then we can't have the compile unit,
      // function, block, line entry or symbol, so we can safely call
      // ResolveSymbolContextForAddress with our symbol context member m_sc.
      if (m_sc.target_sp) {
        resolved |= m_sc.target_sp->GetImages().ResolveSymbolContextForAddress(
            lookup_addr, resolve_scope, m_sc);
      }
    }

    // Update our internal flags so we remember what we have tried to locate so
    // we don't have to keep trying when more calls to this function are made.
    // We might have dug up more information that was requested (for example if
    // we were asked to only get the block, we will have gotten the compile
    // unit, and function) so set any additional bits that we resolved
    m_flags.Set(resolve_scope | resolved);
  }

  // Return the symbol context with everything that was possible to resolve
  // resolved.
  return m_sc;
}

VariableList *StackFrame::GetVariableList(bool get_file_globals) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (m_flags.IsClear(RESOLVED_VARIABLES)) {
    m_flags.Set(RESOLVED_VARIABLES);

    Block *frame_block = GetFrameBlock();

    if (frame_block) {
      const bool get_child_variables = true;
      const bool can_create = true;
      const bool stop_if_child_block_is_inlined_function = true;
      m_variable_list_sp = std::make_shared<VariableList>();
      frame_block->AppendBlockVariables(can_create, get_child_variables,
                                        stop_if_child_block_is_inlined_function,
                                        [](Variable *v) { return true; },
                                        m_variable_list_sp.get());
    }
  }

  if (m_flags.IsClear(RESOLVED_GLOBAL_VARIABLES) && get_file_globals) {
    m_flags.Set(RESOLVED_GLOBAL_VARIABLES);

    if (m_flags.IsClear(eSymbolContextCompUnit))
      GetSymbolContext(eSymbolContextCompUnit);

    if (m_sc.comp_unit) {
      VariableListSP global_variable_list_sp(
          m_sc.comp_unit->GetVariableList(true));
      if (m_variable_list_sp)
        m_variable_list_sp->AddVariables(global_variable_list_sp.get());
      else
        m_variable_list_sp = global_variable_list_sp;
    }
  }

  return m_variable_list_sp.get();
}

VariableListSP
StackFrame::GetInScopeVariableList(bool get_file_globals,
                                   bool must_have_valid_location) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  // We can't fetch variable information for a history stack frame.
  if (IsHistorical())
    return VariableListSP();

  VariableListSP var_list_sp(new VariableList);
  GetSymbolContext(eSymbolContextCompUnit | eSymbolContextBlock);

  if (m_sc.block) {
    const bool can_create = true;
    const bool get_parent_variables = true;
    const bool stop_if_block_is_inlined_function = true;
    m_sc.block->AppendVariables(
        can_create, get_parent_variables, stop_if_block_is_inlined_function,
        [this, must_have_valid_location](Variable *v) {
          return v->IsInScope(this) && (!must_have_valid_location ||
                                        v->LocationIsValidForFrame(this));
        },
        var_list_sp.get());
  }

  if (m_sc.comp_unit && get_file_globals) {
    VariableListSP global_variable_list_sp(
        m_sc.comp_unit->GetVariableList(true));
    if (global_variable_list_sp)
      var_list_sp->AddVariables(global_variable_list_sp.get());
  }

  return var_list_sp;
}

ValueObjectSP StackFrame::GetValueForVariableExpressionPath(
    llvm::StringRef var_expr, DynamicValueType use_dynamic, uint32_t options,
    VariableSP &var_sp, Status &error) {
  llvm::StringRef original_var_expr = var_expr;
  // We can't fetch variable information for a history stack frame.
  if (IsHistorical())
    return ValueObjectSP();

  if (var_expr.empty()) {
    error.SetErrorStringWithFormat("invalid variable path '%s'",
                                   var_expr.str().c_str());
    return ValueObjectSP();
  }

  const bool check_ptr_vs_member =
      (options & eExpressionPathOptionCheckPtrVsMember) != 0;
  const bool no_fragile_ivar =
      (options & eExpressionPathOptionsNoFragileObjcIvar) != 0;
  const bool no_synth_child =
      (options & eExpressionPathOptionsNoSyntheticChildren) != 0;
  // const bool no_synth_array = (options &
  // eExpressionPathOptionsNoSyntheticArrayRange) != 0;
  error.Clear();
  bool deref = false;
  bool address_of = false;
  ValueObjectSP valobj_sp;
  const bool get_file_globals = true;
  // When looking up a variable for an expression, we need only consider the
  // variables that are in scope.
  VariableListSP var_list_sp(GetInScopeVariableList(get_file_globals));
  VariableList *variable_list = var_list_sp.get();

  if (!variable_list)
    return ValueObjectSP();

  // If first character is a '*', then show pointer contents
  std::string var_expr_storage;
  if (var_expr[0] == '*') {
    deref = true;
    var_expr = var_expr.drop_front(); // Skip the '*'
  } else if (var_expr[0] == '&') {
    address_of = true;
    var_expr = var_expr.drop_front(); // Skip the '&'
  }

  size_t separator_idx = var_expr.find_first_of(".-[=+~|&^%#@!/?,<>{}");
  StreamString var_expr_path_strm;

  ConstString name_const_string(var_expr.substr(0, separator_idx));

  var_sp = variable_list->FindVariable(name_const_string, false);

  bool synthetically_added_instance_object = false;

  if (var_sp) {
    var_expr = var_expr.drop_front(name_const_string.GetLength());
  }

  if (!var_sp && (options & eExpressionPathOptionsAllowDirectIVarAccess)) {
    // Check for direct ivars access which helps us with implicit access to
    // ivars with the "this->" or "self->"
    GetSymbolContext(eSymbolContextFunction | eSymbolContextBlock);
    lldb::LanguageType method_language = eLanguageTypeUnknown;
    bool is_instance_method = false;
    ConstString method_object_name;
    if (m_sc.GetFunctionMethodInfo(method_language, is_instance_method,
                                   method_object_name)) {
      if (is_instance_method && method_object_name) {
        var_sp = variable_list->FindVariable(method_object_name);
        if (var_sp) {
          separator_idx = 0;
          var_expr_storage = "->";
          var_expr_storage += var_expr;
          var_expr = var_expr_storage;
          synthetically_added_instance_object = true;
        }
      }
    }
  }

  if (!var_sp && (options & eExpressionPathOptionsInspectAnonymousUnions)) {
    // Check if any anonymous unions are there which contain a variable with
    // the name we need
    for (size_t i = 0; i < variable_list->GetSize(); i++) {
      VariableSP variable_sp = variable_list->GetVariableAtIndex(i);
      if (!variable_sp)
        continue;
      if (!variable_sp->GetName().IsEmpty())
        continue;

      Type *var_type = variable_sp->GetType();
      if (!var_type)
        continue;

      if (!var_type->GetForwardCompilerType().IsAnonymousType())
        continue;
      valobj_sp = GetValueObjectForFrameVariable(variable_sp, use_dynamic);
      if (!valobj_sp)
        return valobj_sp;
      valobj_sp = valobj_sp->GetChildMemberWithName(name_const_string, true);
      if (valobj_sp)
        break;
    }
  }

  if (var_sp && !valobj_sp) {
    valobj_sp = GetValueObjectForFrameVariable(var_sp, use_dynamic);
    if (!valobj_sp)
      return valobj_sp;
  }
  if (!valobj_sp) {
    error.SetErrorStringWithFormat("no variable named '%s' found in this frame",
                                   name_const_string.GetCString());
    return ValueObjectSP();
  }

  // We are dumping at least one child
  while (separator_idx != std::string::npos) {
    // Calculate the next separator index ahead of time
    ValueObjectSP child_valobj_sp;
    const char separator_type = var_expr[0];
    bool expr_is_ptr = false;
    switch (separator_type) {
    case '-':
      expr_is_ptr = true;
      if (var_expr.size() >= 2 && var_expr[1] != '>')
        return ValueObjectSP();

      if (no_fragile_ivar) {
        // Make sure we aren't trying to deref an objective
        // C ivar if this is not allowed
        const uint32_t pointer_type_flags =
            valobj_sp->GetCompilerType().GetTypeInfo(nullptr);
        if ((pointer_type_flags & eTypeIsObjC) &&
            (pointer_type_flags & eTypeIsPointer)) {
          // This was an objective C object pointer and it was requested we
          // skip any fragile ivars so return nothing here
          return ValueObjectSP();
        }
      }

      // If we have a non pointer type with a sythetic value then lets check if
      // we have an sythetic dereference specified.
      if (!valobj_sp->IsPointerType() && valobj_sp->HasSyntheticValue()) {
        Status deref_error;
        if (valobj_sp->GetCompilerType().IsReferenceType()) {
          valobj_sp = valobj_sp->GetSyntheticValue()->Dereference(deref_error);
          if (error.Fail()) {
            error.SetErrorStringWithFormatv(
                "Failed to dereference reference type: %s", deref_error);
            return ValueObjectSP();
          }
        }

        valobj_sp = valobj_sp->Dereference(deref_error);
        if (error.Fail()) {
          error.SetErrorStringWithFormatv(
              "Failed to dereference sythetic value: {0}", deref_error);
          return ValueObjectSP();
        }
        // Some synthetic plug-ins fail to set the error in Dereference
        if (!valobj_sp) {
          error.SetErrorString("Failed to dereference sythetic value");
          return ValueObjectSP();
        }
        expr_is_ptr = false;
      }

      var_expr = var_expr.drop_front(); // Remove the '-'
      LLVM_FALLTHROUGH;
    case '.': {
      var_expr = var_expr.drop_front(); // Remove the '.' or '>'
      separator_idx = var_expr.find_first_of(".-[");
      ConstString child_name(var_expr.substr(0, var_expr.find_first_of(".-[")));

      if (check_ptr_vs_member) {
        // We either have a pointer type and need to verify valobj_sp is a
        // pointer, or we have a member of a class/union/struct being accessed
        // with the . syntax and need to verify we don't have a pointer.
        const bool actual_is_ptr = valobj_sp->IsPointerType();

        if (actual_is_ptr != expr_is_ptr) {
          // Incorrect use of "." with a pointer, or "->" with a
          // class/union/struct instance or reference.
          valobj_sp->GetExpressionPath(var_expr_path_strm, false);
          if (actual_is_ptr)
            error.SetErrorStringWithFormat(
                "\"%s\" is a pointer and . was used to attempt to access "
                "\"%s\". Did you mean \"%s->%s\"?",
                var_expr_path_strm.GetData(), child_name.GetCString(),
                var_expr_path_strm.GetData(), var_expr.str().c_str());
          else
            error.SetErrorStringWithFormat(
                "\"%s\" is not a pointer and -> was used to attempt to "
                "access \"%s\". Did you mean \"%s.%s\"?",
                var_expr_path_strm.GetData(), child_name.GetCString(),
                var_expr_path_strm.GetData(), var_expr.str().c_str());
          return ValueObjectSP();
        }
      }
      child_valobj_sp = valobj_sp->GetChildMemberWithName(child_name, true);
      if (!child_valobj_sp) {
        if (!no_synth_child) {
          child_valobj_sp = valobj_sp->GetSyntheticValue();
          if (child_valobj_sp)
            child_valobj_sp =
                child_valobj_sp->GetChildMemberWithName(child_name, true);
        }

        if (no_synth_child || !child_valobj_sp) {
          // No child member with name "child_name"
          if (synthetically_added_instance_object) {
            // We added a "this->" or "self->" to the beginning of the
            // expression and this is the first pointer ivar access, so just
            // return the normal error
            error.SetErrorStringWithFormat(
                "no variable or instance variable named '%s' found in "
                "this frame",
                name_const_string.GetCString());
          } else {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            if (child_name) {
              error.SetErrorStringWithFormat(
                  "\"%s\" is not a member of \"(%s) %s\"",
                  child_name.GetCString(),
                  valobj_sp->GetTypeName().AsCString("<invalid type>"),
                  var_expr_path_strm.GetData());
            } else {
              error.SetErrorStringWithFormat(
                  "incomplete expression path after \"%s\" in \"%s\"",
                  var_expr_path_strm.GetData(),
                  original_var_expr.str().c_str());
            }
          }
          return ValueObjectSP();
        }
      }
      synthetically_added_instance_object = false;
      // Remove the child name from the path
      var_expr = var_expr.drop_front(child_name.GetLength());
      if (use_dynamic != eNoDynamicValues) {
        ValueObjectSP dynamic_value_sp(
            child_valobj_sp->GetDynamicValue(use_dynamic));
        if (dynamic_value_sp)
          child_valobj_sp = dynamic_value_sp;
      }
    } break;

    case '[': {
      // Array member access, or treating pointer as an array Need at least two
      // brackets and a number
      if (var_expr.size() <= 2) {
        error.SetErrorStringWithFormat(
            "invalid square bracket encountered after \"%s\" in \"%s\"",
            var_expr_path_strm.GetData(), var_expr.str().c_str());
        return ValueObjectSP();
      }

      // Drop the open brace.
      var_expr = var_expr.drop_front();
      long child_index = 0;

      // If there's no closing brace, this is an invalid expression.
      size_t end_pos = var_expr.find_first_of(']');
      if (end_pos == llvm::StringRef::npos) {
        error.SetErrorStringWithFormat(
            "missing closing square bracket in expression \"%s\"",
            var_expr_path_strm.GetData());
        return ValueObjectSP();
      }
      llvm::StringRef index_expr = var_expr.take_front(end_pos);
      llvm::StringRef original_index_expr = index_expr;
      // Drop all of "[index_expr]"
      var_expr = var_expr.drop_front(end_pos + 1);

      if (index_expr.consumeInteger(0, child_index)) {
        // If there was no integer anywhere in the index expression, this is
        // erroneous expression.
        error.SetErrorStringWithFormat("invalid index expression \"%s\"",
                                       index_expr.str().c_str());
        return ValueObjectSP();
      }

      if (index_expr.empty()) {
        // The entire index expression was a single integer.

        if (valobj_sp->GetCompilerType().IsPointerToScalarType() && deref) {
          // what we have is *ptr[low]. the most similar C++ syntax is to deref
          // ptr and extract bit low out of it. reading array item low would be
          // done by saying ptr[low], without a deref * sign
          Status error;
          ValueObjectSP temp(valobj_sp->Dereference(error));
          if (error.Fail()) {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "could not dereference \"(%s) %s\"",
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
            return ValueObjectSP();
          }
          valobj_sp = temp;
          deref = false;
        } else if (valobj_sp->GetCompilerType().IsArrayOfScalarType() &&
                   deref) {
          // what we have is *arr[low]. the most similar C++ syntax is to get
          // arr[0] (an operation that is equivalent to deref-ing arr) and
          // extract bit low out of it. reading array item low would be done by
          // saying arr[low], without a deref * sign
          Status error;
          ValueObjectSP temp(valobj_sp->GetChildAtIndex(0, true));
          if (error.Fail()) {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "could not get item 0 for \"(%s) %s\"",
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
            return ValueObjectSP();
          }
          valobj_sp = temp;
          deref = false;
        }

        bool is_incomplete_array = false;
        if (valobj_sp->IsPointerType()) {
          bool is_objc_pointer = true;

          if (valobj_sp->GetCompilerType().GetMinimumLanguage() !=
              eLanguageTypeObjC)
            is_objc_pointer = false;
          else if (!valobj_sp->GetCompilerType().IsPointerType())
            is_objc_pointer = false;

          if (no_synth_child && is_objc_pointer) {
            error.SetErrorStringWithFormat(
                "\"(%s) %s\" is an Objective-C pointer, and cannot be "
                "subscripted",
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());

            return ValueObjectSP();
          } else if (is_objc_pointer) {
            // dereferencing ObjC variables is not valid.. so let's try and
            // recur to synthetic children
            ValueObjectSP synthetic = valobj_sp->GetSyntheticValue();
            if (!synthetic                 /* no synthetic */
                || synthetic == valobj_sp) /* synthetic is the same as
                                              the original object */
            {
              valobj_sp->GetExpressionPath(var_expr_path_strm, false);
              error.SetErrorStringWithFormat(
                  "\"(%s) %s\" is not an array type",
                  valobj_sp->GetTypeName().AsCString("<invalid type>"),
                  var_expr_path_strm.GetData());
            } else if (
                static_cast<uint32_t>(child_index) >=
                synthetic
                    ->GetNumChildren() /* synthetic does not have that many values */) {
              valobj_sp->GetExpressionPath(var_expr_path_strm, false);
              error.SetErrorStringWithFormat(
                  "array index %ld is not valid for \"(%s) %s\"", child_index,
                  valobj_sp->GetTypeName().AsCString("<invalid type>"),
                  var_expr_path_strm.GetData());
            } else {
              child_valobj_sp = synthetic->GetChildAtIndex(child_index, true);
              if (!child_valobj_sp) {
                valobj_sp->GetExpressionPath(var_expr_path_strm, false);
                error.SetErrorStringWithFormat(
                    "array index %ld is not valid for \"(%s) %s\"", child_index,
                    valobj_sp->GetTypeName().AsCString("<invalid type>"),
                    var_expr_path_strm.GetData());
              }
            }
          } else {
            child_valobj_sp =
                valobj_sp->GetSyntheticArrayMember(child_index, true);
            if (!child_valobj_sp) {
              valobj_sp->GetExpressionPath(var_expr_path_strm, false);
              error.SetErrorStringWithFormat(
                  "failed to use pointer as array for index %ld for "
                  "\"(%s) %s\"",
                  child_index,
                  valobj_sp->GetTypeName().AsCString("<invalid type>"),
                  var_expr_path_strm.GetData());
            }
          }
        } else if (valobj_sp->GetCompilerType().IsArrayType(
                       nullptr, nullptr, &is_incomplete_array)) {
          // Pass false to dynamic_value here so we can tell the difference
          // between no dynamic value and no member of this type...
          child_valobj_sp = valobj_sp->GetChildAtIndex(child_index, true);
          if (!child_valobj_sp && (is_incomplete_array || !no_synth_child))
            child_valobj_sp =
                valobj_sp->GetSyntheticArrayMember(child_index, true);

          if (!child_valobj_sp) {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "array index %ld is not valid for \"(%s) %s\"", child_index,
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
          }
        } else if (valobj_sp->GetCompilerType().IsScalarType()) {
          // this is a bitfield asking to display just one bit
          child_valobj_sp = valobj_sp->GetSyntheticBitFieldChild(
              child_index, child_index, true);
          if (!child_valobj_sp) {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "bitfield range %ld-%ld is not valid for \"(%s) %s\"",
                child_index, child_index,
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
          }
        } else {
          ValueObjectSP synthetic = valobj_sp->GetSyntheticValue();
          if (no_synth_child /* synthetic is forbidden */ ||
              !synthetic                 /* no synthetic */
              || synthetic == valobj_sp) /* synthetic is the same as the
                                            original object */
          {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "\"(%s) %s\" is not an array type",
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
          } else if (
              static_cast<uint32_t>(child_index) >=
              synthetic
                  ->GetNumChildren() /* synthetic does not have that many values */) {
            valobj_sp->GetExpressionPath(var_expr_path_strm, false);
            error.SetErrorStringWithFormat(
                "array index %ld is not valid for \"(%s) %s\"", child_index,
                valobj_sp->GetTypeName().AsCString("<invalid type>"),
                var_expr_path_strm.GetData());
          } else {
            child_valobj_sp = synthetic->GetChildAtIndex(child_index, true);
            if (!child_valobj_sp) {
              valobj_sp->GetExpressionPath(var_expr_path_strm, false);
              error.SetErrorStringWithFormat(
                  "array index %ld is not valid for \"(%s) %s\"", child_index,
                  valobj_sp->GetTypeName().AsCString("<invalid type>"),
                  var_expr_path_strm.GetData());
            }
          }
        }

        if (!child_valobj_sp) {
          // Invalid array index...
          return ValueObjectSP();
        }

        separator_idx = var_expr.find_first_of(".-[");
        if (use_dynamic != eNoDynamicValues) {
          ValueObjectSP dynamic_value_sp(
              child_valobj_sp->GetDynamicValue(use_dynamic));
          if (dynamic_value_sp)
            child_valobj_sp = dynamic_value_sp;
        }
        // Break out early from the switch since we were able to find the child
        // member
        break;
      }

      // this is most probably a BitField, let's take a look
      if (index_expr.front() != '-') {
        error.SetErrorStringWithFormat("invalid range expression \"'%s'\"",
                                       original_index_expr.str().c_str());
        return ValueObjectSP();
      }

      index_expr = index_expr.drop_front();
      long final_index = 0;
      if (index_expr.getAsInteger(0, final_index)) {
        error.SetErrorStringWithFormat("invalid range expression \"'%s'\"",
                                       original_index_expr.str().c_str());
        return ValueObjectSP();
      }

      // if the format given is [high-low], swap range
      if (child_index > final_index) {
        long temp = child_index;
        child_index = final_index;
        final_index = temp;
      }

      if (valobj_sp->GetCompilerType().IsPointerToScalarType() && deref) {
        // what we have is *ptr[low-high]. the most similar C++ syntax is to
        // deref ptr and extract bits low thru high out of it. reading array
        // items low thru high would be done by saying ptr[low-high], without a
        // deref * sign
        Status error;
        ValueObjectSP temp(valobj_sp->Dereference(error));
        if (error.Fail()) {
          valobj_sp->GetExpressionPath(var_expr_path_strm, false);
          error.SetErrorStringWithFormat(
              "could not dereference \"(%s) %s\"",
              valobj_sp->GetTypeName().AsCString("<invalid type>"),
              var_expr_path_strm.GetData());
          return ValueObjectSP();
        }
        valobj_sp = temp;
        deref = false;
      } else if (valobj_sp->GetCompilerType().IsArrayOfScalarType() && deref) {
        // what we have is *arr[low-high]. the most similar C++ syntax is to
        // get arr[0] (an operation that is equivalent to deref-ing arr) and
        // extract bits low thru high out of it. reading array items low thru
        // high would be done by saying arr[low-high], without a deref * sign
        Status error;
        ValueObjectSP temp(valobj_sp->GetChildAtIndex(0, true));
        if (error.Fail()) {
          valobj_sp->GetExpressionPath(var_expr_path_strm, false);
          error.SetErrorStringWithFormat(
              "could not get item 0 for \"(%s) %s\"",
              valobj_sp->GetTypeName().AsCString("<invalid type>"),
              var_expr_path_strm.GetData());
          return ValueObjectSP();
        }
        valobj_sp = temp;
        deref = false;
      }

      child_valobj_sp =
          valobj_sp->GetSyntheticBitFieldChild(child_index, final_index, true);
      if (!child_valobj_sp) {
        valobj_sp->GetExpressionPath(var_expr_path_strm, false);
        error.SetErrorStringWithFormat(
            "bitfield range %ld-%ld is not valid for \"(%s) %s\"", child_index,
            final_index, valobj_sp->GetTypeName().AsCString("<invalid type>"),
            var_expr_path_strm.GetData());
      }

      if (!child_valobj_sp) {
        // Invalid bitfield range...
        return ValueObjectSP();
      }

      separator_idx = var_expr.find_first_of(".-[");
      if (use_dynamic != eNoDynamicValues) {
        ValueObjectSP dynamic_value_sp(
            child_valobj_sp->GetDynamicValue(use_dynamic));
        if (dynamic_value_sp)
          child_valobj_sp = dynamic_value_sp;
      }
      // Break out early from the switch since we were able to find the child
      // member
      break;
    }
    default:
      // Failure...
      {
        valobj_sp->GetExpressionPath(var_expr_path_strm, false);
        error.SetErrorStringWithFormat(
            "unexpected char '%c' encountered after \"%s\" in \"%s\"",
            separator_type, var_expr_path_strm.GetData(),
            var_expr.str().c_str());

        return ValueObjectSP();
      }
    }

    if (child_valobj_sp)
      valobj_sp = child_valobj_sp;

    if (var_expr.empty())
      break;
  }
  if (valobj_sp) {
    if (deref) {
      ValueObjectSP deref_valobj_sp(valobj_sp->Dereference(error));
      valobj_sp = deref_valobj_sp;
    } else if (address_of) {
      ValueObjectSP address_of_valobj_sp(valobj_sp->AddressOf(error));
      valobj_sp = address_of_valobj_sp;
    }
  }
  return valobj_sp;
}

bool StackFrame::GetFrameBaseValue(Scalar &frame_base, Status *error_ptr) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (!m_cfa_is_valid) {
    m_frame_base_error.SetErrorString(
        "No frame base available for this historical stack frame.");
    return false;
  }

  if (m_flags.IsClear(GOT_FRAME_BASE)) {
    if (m_sc.function) {
      m_frame_base.Clear();
      m_frame_base_error.Clear();

      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().IsLocationList())
        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);
      }
    } else {
      m_frame_base_error.SetErrorString("No function in symbol context.");
    }
  }

  if (m_frame_base_error.Success())
    frame_base = m_frame_base;

  if (error_ptr)
    *error_ptr = m_frame_base_error;
  return m_frame_base_error.Success();
}

DWARFExpression *StackFrame::GetFrameBaseExpression(Status *error_ptr) {
  if (!m_sc.function) {
    if (error_ptr) {
      error_ptr->SetErrorString("No function in symbol context.");
    }
    return nullptr;
  }

  return &m_sc.function->GetFrameBaseExpression();
}

RegisterContextSP StackFrame::GetRegisterContext() {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (!m_reg_context_sp) {
    ThreadSP thread_sp(GetThread());
    if (thread_sp)
      m_reg_context_sp = thread_sp->CreateRegisterContextForFrame(this);
  }
  return m_reg_context_sp;
}

bool StackFrame::HasDebugInformation() {
  GetSymbolContext(eSymbolContextLineEntry);
  return m_sc.line_entry.IsValid();
}

ValueObjectSP
StackFrame::GetValueObjectForFrameVariable(const VariableSP &variable_sp,
                                           DynamicValueType use_dynamic) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  ValueObjectSP valobj_sp;
  if (IsHistorical()) {
    return valobj_sp;
  }
  VariableList *var_list = GetVariableList(true);
  if (var_list) {
    // Make sure the variable is a frame variable
    const uint32_t var_idx = var_list->FindIndexForVariable(variable_sp.get());
    const uint32_t num_variables = var_list->GetSize();
    if (var_idx < num_variables) {
      valobj_sp = m_variable_list_value_objects.GetValueObjectAtIndex(var_idx);
      if (!valobj_sp) {
        if (m_variable_list_value_objects.GetSize() < num_variables)
          m_variable_list_value_objects.Resize(num_variables);
        valobj_sp = ValueObjectVariable::Create(this, variable_sp);
        m_variable_list_value_objects.SetValueObjectAtIndex(var_idx, valobj_sp);
      }
    }
  }
  if (use_dynamic != eNoDynamicValues && valobj_sp) {
    ValueObjectSP dynamic_sp = valobj_sp->GetDynamicValue(use_dynamic);
    if (dynamic_sp)
      return dynamic_sp;
  }
  return valobj_sp;
}

ValueObjectSP StackFrame::TrackGlobalVariable(const VariableSP &variable_sp,
                                              DynamicValueType use_dynamic) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  if (IsHistorical())
    return ValueObjectSP();

  // Check to make sure we aren't already tracking this variable?
  ValueObjectSP valobj_sp(
      GetValueObjectForFrameVariable(variable_sp, use_dynamic));
  if (!valobj_sp) {
    // We aren't already tracking this global
    VariableList *var_list = GetVariableList(true);
    // If this frame has no variables, create a new list
    if (var_list == nullptr)
      m_variable_list_sp = std::make_shared<VariableList>();

    // Add the global/static variable to this frame
    m_variable_list_sp->AddVariable(variable_sp);

    // Now make a value object for it so we can track its changes
    valobj_sp = GetValueObjectForFrameVariable(variable_sp, use_dynamic);
  }
  return valobj_sp;
}

bool StackFrame::IsInlined() {
  if (m_sc.block == nullptr)
    GetSymbolContext(eSymbolContextBlock);
  if (m_sc.block)
    return m_sc.block->GetContainingInlinedBlock() != nullptr;
  return false;
}

bool StackFrame::IsHistorical() const {
  return m_stack_frame_kind == StackFrame::Kind::History;
}

bool StackFrame::IsArtificial() const {
  return m_stack_frame_kind == StackFrame::Kind::Artificial;
}

lldb::LanguageType StackFrame::GetLanguage() {
  CompileUnit *cu = GetSymbolContext(eSymbolContextCompUnit).comp_unit;
  if (cu)
    return cu->GetLanguage();
  return lldb::eLanguageTypeUnknown;
}

lldb::LanguageType StackFrame::GuessLanguage() {
  LanguageType lang_type = GetLanguage();

  if (lang_type == eLanguageTypeUnknown) {
    SymbolContext sc = GetSymbolContext(eSymbolContextFunction 
                                        | eSymbolContextSymbol);
    if (sc.function) {
      lang_type = sc.function->GetMangled().GuessLanguage();
    }
    else if (sc.symbol)
    {
      lang_type = sc.symbol->GetMangled().GuessLanguage();
    }
  }

  return lang_type;
}

namespace {
std::pair<const Instruction::Operand *, int64_t>
GetBaseExplainingValue(const Instruction::Operand &operand,
                       RegisterContext &register_context, lldb::addr_t value) {
  switch (operand.m_type) {
  case Instruction::Operand::Type::Dereference:
  case Instruction::Operand::Type::Immediate:
  case Instruction::Operand::Type::Invalid:
  case Instruction::Operand::Type::Product:
    // These are not currently interesting
    return std::make_pair(nullptr, 0);
  case Instruction::Operand::Type::Sum: {
    const Instruction::Operand *immediate_child = nullptr;
    const Instruction::Operand *variable_child = nullptr;
    if (operand.m_children[0].m_type == Instruction::Operand::Type::Immediate) {
      immediate_child = &operand.m_children[0];
      variable_child = &operand.m_children[1];
    } else if (operand.m_children[1].m_type ==
               Instruction::Operand::Type::Immediate) {
      immediate_child = &operand.m_children[1];
      variable_child = &operand.m_children[0];
    }
    if (!immediate_child) {
      return std::make_pair(nullptr, 0);
    }
    lldb::addr_t adjusted_value = value;
    if (immediate_child->m_negative) {
      adjusted_value += immediate_child->m_immediate;
    } else {
      adjusted_value -= immediate_child->m_immediate;
    }
    std::pair<const Instruction::Operand *, int64_t> base_and_offset =
        GetBaseExplainingValue(*variable_child, register_context,
                               adjusted_value);
    if (!base_and_offset.first) {
      return std::make_pair(nullptr, 0);
    }
    if (immediate_child->m_negative) {
      base_and_offset.second -= immediate_child->m_immediate;
    } else {
      base_and_offset.second += immediate_child->m_immediate;
    }
    return base_and_offset;
  }
  case Instruction::Operand::Type::Register: {
    const RegisterInfo *info =
        register_context.GetRegisterInfoByName(operand.m_register.AsCString());
    if (!info) {
      return std::make_pair(nullptr, 0);
    }
    RegisterValue reg_value;
    if (!register_context.ReadRegister(info, reg_value)) {
      return std::make_pair(nullptr, 0);
    }
    if (reg_value.GetAsUInt64() == value) {
      return std::make_pair(&operand, 0);
    } else {
      return std::make_pair(nullptr, 0);
    }
  }
  }
  return std::make_pair(nullptr, 0);
}

std::pair<const Instruction::Operand *, int64_t>
GetBaseExplainingDereference(const Instruction::Operand &operand,
                             RegisterContext &register_context,
                             lldb::addr_t addr) {
  if (operand.m_type == Instruction::Operand::Type::Dereference) {
    return GetBaseExplainingValue(operand.m_children[0], register_context,
                                  addr);
  }
  return std::make_pair(nullptr, 0);
}
}

lldb::ValueObjectSP StackFrame::GuessValueForAddress(lldb::addr_t addr) {
  TargetSP target_sp = CalculateTarget();

  const ArchSpec &target_arch = target_sp->GetArchitecture();

  AddressRange pc_range;
  pc_range.GetBaseAddress() = GetFrameCodeAddress();
  pc_range.SetByteSize(target_arch.GetMaximumOpcodeByteSize());

  ExecutionContext exe_ctx(shared_from_this());

  const char *plugin_name = nullptr;
  const char *flavor = nullptr;
  const bool prefer_file_cache = false;

  DisassemblerSP disassembler_sp = Disassembler::DisassembleRange(
      target_arch, plugin_name, flavor, exe_ctx, pc_range, prefer_file_cache);

  if (!disassembler_sp || !disassembler_sp->GetInstructionList().GetSize()) {
    return ValueObjectSP();
  }

  InstructionSP instruction_sp =
      disassembler_sp->GetInstructionList().GetInstructionAtIndex(0);

  llvm::SmallVector<Instruction::Operand, 3> operands;

  if (!instruction_sp->ParseOperands(operands)) {
    return ValueObjectSP();
  }

  RegisterContextSP register_context_sp = GetRegisterContext();

  if (!register_context_sp) {
    return ValueObjectSP();
  }

  for (const Instruction::Operand &operand : operands) {
    std::pair<const Instruction::Operand *, int64_t> base_and_offset =
        GetBaseExplainingDereference(operand, *register_context_sp, addr);

    if (!base_and_offset.first) {
      continue;
    }

    switch (base_and_offset.first->m_type) {
    case Instruction::Operand::Type::Immediate: {
      lldb_private::Address addr;
      if (target_sp->ResolveLoadAddress(base_and_offset.first->m_immediate +
                                            base_and_offset.second,
                                        addr)) {
        auto c_type_system_or_err =
            target_sp->GetScratchTypeSystemForLanguage(eLanguageTypeC);
        if (auto err = c_type_system_or_err.takeError()) {
          LLDB_LOG_ERROR(
              lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_THREAD),
              std::move(err), "Unable to guess value for given address");
          return ValueObjectSP();
        } else {
          CompilerType void_ptr_type =
              c_type_system_or_err
                  ->GetBasicTypeFromAST(lldb::BasicType::eBasicTypeChar)
                  .GetPointerType();
          return ValueObjectMemory::Create(this, "", addr, void_ptr_type);
        }
      } else {
        return ValueObjectSP();
      }
      break;
    }
    case Instruction::Operand::Type::Register: {
      return GuessValueForRegisterAndOffset(base_and_offset.first->m_register,
                                            base_and_offset.second);
    }
    default:
      return ValueObjectSP();
    }
  }

  return ValueObjectSP();
}

namespace {
ValueObjectSP GetValueForOffset(StackFrame &frame, ValueObjectSP &parent,
                                int64_t offset) {
  if (offset < 0 || uint64_t(offset) >= parent->GetByteSize()) {
    return ValueObjectSP();
  }

  if (parent->IsPointerOrReferenceType()) {
    return parent;
  }

  for (int ci = 0, ce = parent->GetNumChildren(); ci != ce; ++ci) {
    const bool can_create = true;
    ValueObjectSP child_sp = parent->GetChildAtIndex(ci, can_create);

    if (!child_sp) {
      return ValueObjectSP();
    }

    int64_t child_offset = child_sp->GetByteOffset();
    int64_t child_size = child_sp->GetByteSize();

    if (offset >= child_offset && offset < (child_offset + child_size)) {
      return GetValueForOffset(frame, child_sp, offset - child_offset);
    }
  }

  if (offset == 0) {
    return parent;
  } else {
    return ValueObjectSP();
  }
}

ValueObjectSP GetValueForDereferincingOffset(StackFrame &frame,
                                             ValueObjectSP &base,
                                             int64_t offset) {
  // base is a pointer to something
  // offset is the thing to add to the pointer We return the most sensible
  // ValueObject for the result of *(base+offset)

  if (!base->IsPointerOrReferenceType()) {
    return ValueObjectSP();
  }

  Status error;
  ValueObjectSP pointee = base->Dereference(error);
    
  if (!pointee) {
    return ValueObjectSP();
  }

  if (offset >= 0 && uint64_t(offset) >= pointee->GetByteSize()) {
    int64_t index = offset / pointee->GetByteSize();
    offset = offset % pointee->GetByteSize();
    const bool can_create = true;
    pointee = base->GetSyntheticArrayMember(index, can_create);
  }

  if (!pointee || error.Fail()) {
    return ValueObjectSP();
  }

  return GetValueForOffset(frame, pointee, offset);
}

/// Attempt to reconstruct the ValueObject for the address contained in a
/// given register plus an offset.
///
/// \params [in] frame
///   The current stack frame.
///
/// \params [in] reg
///   The register.
///
/// \params [in] offset
///   The offset from the register.
///
/// \param [in] disassembler
///   A disassembler containing instructions valid up to the current PC.
///
/// \param [in] variables
///   The variable list from the current frame,
///
/// \param [in] pc
///   The program counter for the instruction considered the 'user'.
///
/// \return
///   A string describing the base for the ExpressionPath.  This could be a
///     variable, a register value, an argument, or a function return value.
///   The ValueObject if found.  If valid, it has a valid ExpressionPath.
lldb::ValueObjectSP DoGuessValueAt(StackFrame &frame, ConstString reg,
                                   int64_t offset, Disassembler &disassembler,
                                   VariableList &variables, const Address &pc) {
  // Example of operation for Intel:
  //
  // +14: movq   -0x8(%rbp), %rdi
  // +18: movq   0x8(%rdi), %rdi
  // +22: addl   0x4(%rdi), %eax
  //
  // f, a pointer to a struct, is known to be at -0x8(%rbp).
  //
  // DoGuessValueAt(frame, rdi, 4, dis, vars, 0x22) finds the instruction at
  // +18 that assigns to rdi, and calls itself recursively for that dereference
  //   DoGuessValueAt(frame, rdi, 8, dis, vars, 0x18) finds the instruction at
  //   +14 that assigns to rdi, and calls itself recursively for that
  //   derefernece
  //     DoGuessValueAt(frame, rbp, -8, dis, vars, 0x14) finds "f" in the
  //     variable list.
  //     Returns a ValueObject for f.  (That's what was stored at rbp-8 at +14)
  //   Returns a ValueObject for *(f+8) or f->b (That's what was stored at rdi+8
  //   at +18)
  // Returns a ValueObject for *(f->b+4) or f->b->a (That's what was stored at
  // rdi+4 at +22)

  // First, check the variable list to see if anything is at the specified
  // location.

  using namespace OperandMatchers;

  const RegisterInfo *reg_info =
      frame.GetRegisterContext()->GetRegisterInfoByName(reg.AsCString());
  if (!reg_info) {
    return ValueObjectSP();
  }

  Instruction::Operand op =
      offset ? Instruction::Operand::BuildDereference(
                   Instruction::Operand::BuildSum(
                       Instruction::Operand::BuildRegister(reg),
                       Instruction::Operand::BuildImmediate(offset)))
             : Instruction::Operand::BuildDereference(
                   Instruction::Operand::BuildRegister(reg));

  for (size_t vi = 0, ve = variables.GetSize(); vi != ve; ++vi) {
    VariableSP var_sp = variables.GetVariableAtIndex(vi);
    if (var_sp->LocationExpression().MatchesOperand(frame, op)) {
      return frame.GetValueObjectForFrameVariable(var_sp, eNoDynamicValues);
    }
  }

  const uint32_t current_inst =
      disassembler.GetInstructionList().GetIndexOfInstructionAtAddress(pc);
  if (current_inst == UINT32_MAX) {
    return ValueObjectSP();
  }

  for (uint32_t ii = current_inst - 1; ii != (uint32_t)-1; --ii) {
    // This is not an exact algorithm, and it sacrifices accuracy for
    // generality.  Recognizing "mov" and "ld" instructions –– and which
    // are their source and destination operands -- is something the
    // disassembler should do for us.
    InstructionSP instruction_sp =
        disassembler.GetInstructionList().GetInstructionAtIndex(ii);

    if (instruction_sp->IsCall()) {
      ABISP abi_sp = frame.CalculateProcess()->GetABI();
      if (!abi_sp) {
        continue;
      }

      const char *return_register_name;
      if (!abi_sp->GetPointerReturnRegister(return_register_name)) {
        continue;
      }

      const RegisterInfo *return_register_info =
          frame.GetRegisterContext()->GetRegisterInfoByName(
              return_register_name);
      if (!return_register_info) {
        continue;
      }

      int64_t offset = 0;

      if (!MatchUnaryOp(MatchOpType(Instruction::Operand::Type::Dereference),
                        MatchRegOp(*return_register_info))(op) &&
          !MatchUnaryOp(
              MatchOpType(Instruction::Operand::Type::Dereference),
              MatchBinaryOp(MatchOpType(Instruction::Operand::Type::Sum),
                            MatchRegOp(*return_register_info),
                            FetchImmOp(offset)))(op)) {
        continue;
      }

      llvm::SmallVector<Instruction::Operand, 1> operands;
      if (!instruction_sp->ParseOperands(operands) || operands.size() != 1) {
        continue;
      }

      switch (operands[0].m_type) {
      default:
        break;
      case Instruction::Operand::Type::Immediate: {
        SymbolContext sc;
        Address load_address;
        if (!frame.CalculateTarget()->ResolveLoadAddress(
                operands[0].m_immediate, load_address)) {
          break;
        }
        frame.CalculateTarget()->GetImages().ResolveSymbolContextForAddress(
            load_address, eSymbolContextFunction, sc);
        if (!sc.function) {
          break;
        }
        CompilerType function_type = sc.function->GetCompilerType();
        if (!function_type.IsFunctionType()) {
          break;
        }
        CompilerType return_type = function_type.GetFunctionReturnType();
        RegisterValue return_value;
        if (!frame.GetRegisterContext()->ReadRegister(return_register_info,
                                                      return_value)) {
          break;
        }
        std::string name_str(
            sc.function->GetName().AsCString("<unknown function>"));
        name_str.append("()");
        Address return_value_address(return_value.GetAsUInt64());
        ValueObjectSP return_value_sp = ValueObjectMemory::Create(
            &frame, name_str, return_value_address, return_type);
        return GetValueForDereferincingOffset(frame, return_value_sp, offset);
      }
      }

      continue;
    }

    llvm::SmallVector<Instruction::Operand, 2> operands;
    if (!instruction_sp->ParseOperands(operands) || operands.size() != 2) {
      continue;
    }

    Instruction::Operand *origin_operand = nullptr;
    auto clobbered_reg_matcher = [reg_info](const Instruction::Operand &op) {
      return MatchRegOp(*reg_info)(op) && op.m_clobbered;
    };

    if (clobbered_reg_matcher(operands[0])) {
      origin_operand = &operands[1];
    }
    else if (clobbered_reg_matcher(operands[1])) {
      origin_operand = &operands[0];
    }
    else {
      continue;
    }

    // We have an origin operand.  Can we track its value down?
    ValueObjectSP source_path;
    ConstString origin_register;
    int64_t origin_offset = 0;

    if (FetchRegOp(origin_register)(*origin_operand)) {
      source_path = DoGuessValueAt(frame, origin_register, 0, disassembler,
                                   variables, instruction_sp->GetAddress());
    } else if (MatchUnaryOp(
                   MatchOpType(Instruction::Operand::Type::Dereference),
                   FetchRegOp(origin_register))(*origin_operand) ||
               MatchUnaryOp(
                   MatchOpType(Instruction::Operand::Type::Dereference),
                   MatchBinaryOp(MatchOpType(Instruction::Operand::Type::Sum),
                                 FetchRegOp(origin_register),
                                 FetchImmOp(origin_offset)))(*origin_operand)) {
      source_path =
          DoGuessValueAt(frame, origin_register, origin_offset, disassembler,
                         variables, instruction_sp->GetAddress());
      if (!source_path) {
        continue;
      }
      source_path =
          GetValueForDereferincingOffset(frame, source_path, offset);
    }

    if (source_path) {
      return source_path;
    }
  }

  return ValueObjectSP();
}
}

lldb::ValueObjectSP StackFrame::GuessValueForRegisterAndOffset(ConstString reg,
                                                               int64_t offset) {
  TargetSP target_sp = CalculateTarget();

  const ArchSpec &target_arch = target_sp->GetArchitecture();

  Block *frame_block = GetFrameBlock();

  if (!frame_block) {
    return ValueObjectSP();
  }

  Function *function = frame_block->CalculateSymbolContextFunction();
  if (!function) {
    return ValueObjectSP();
  }

  AddressRange pc_range = function->GetAddressRange();

  if (GetFrameCodeAddress().GetFileAddress() <
          pc_range.GetBaseAddress().GetFileAddress() ||
      GetFrameCodeAddress().GetFileAddress() -
              pc_range.GetBaseAddress().GetFileAddress() >=
          pc_range.GetByteSize()) {
    return ValueObjectSP();
  }

  ExecutionContext exe_ctx(shared_from_this());

  const char *plugin_name = nullptr;
  const char *flavor = nullptr;
  const bool prefer_file_cache = false;
  DisassemblerSP disassembler_sp = Disassembler::DisassembleRange(
      target_arch, plugin_name, flavor, exe_ctx, pc_range, prefer_file_cache);

  if (!disassembler_sp || !disassembler_sp->GetInstructionList().GetSize()) {
    return ValueObjectSP();
  }

  const bool get_file_globals = false;
  VariableList *variables = GetVariableList(get_file_globals);

  if (!variables) {
    return ValueObjectSP();
  }

  return DoGuessValueAt(*this, reg, offset, *disassembler_sp, *variables,
                        GetFrameCodeAddress());
}

lldb::ValueObjectSP StackFrame::FindVariable(ConstString name) {
  ValueObjectSP value_sp;

  if (!name)
    return value_sp;

  TargetSP target_sp = CalculateTarget();
  ProcessSP process_sp = CalculateProcess();

  if (!target_sp && !process_sp)
    return value_sp;

  VariableList variable_list;
  VariableSP var_sp;
  SymbolContext sc(GetSymbolContext(eSymbolContextBlock));

  if (sc.block) {
    const bool can_create = true;
    const bool get_parent_variables = true;
    const bool stop_if_block_is_inlined_function = true;

    if (sc.block->AppendVariables(
            can_create, get_parent_variables, stop_if_block_is_inlined_function,
            [this](Variable *v) { return v->IsInScope(this); },
            &variable_list)) {
      var_sp = variable_list.FindVariable(name);
    }

    if (var_sp)
      value_sp = GetValueObjectForFrameVariable(var_sp, eNoDynamicValues);
  }

  return value_sp;
}

TargetSP StackFrame::CalculateTarget() {
  TargetSP target_sp;
  ThreadSP thread_sp(GetThread());
  if (thread_sp) {
    ProcessSP process_sp(thread_sp->CalculateProcess());
    if (process_sp)
      target_sp = process_sp->CalculateTarget();
  }
  return target_sp;
}

ProcessSP StackFrame::CalculateProcess() {
  ProcessSP process_sp;
  ThreadSP thread_sp(GetThread());
  if (thread_sp)
    process_sp = thread_sp->CalculateProcess();
  return process_sp;
}

ThreadSP StackFrame::CalculateThread() { return GetThread(); }

StackFrameSP StackFrame::CalculateStackFrame() { return shared_from_this(); }

void StackFrame::CalculateExecutionContext(ExecutionContext &exe_ctx) {
  exe_ctx.SetContext(shared_from_this());
}

void StackFrame::DumpUsingSettingsFormat(Stream *strm, bool show_unique,
                                         const char *frame_marker) {
  if (strm == nullptr)
    return;

  GetSymbolContext(eSymbolContextEverything);
  ExecutionContext exe_ctx(shared_from_this());
  StreamString s;

  if (frame_marker)
    s.PutCString(frame_marker);

  const FormatEntity::Entry *frame_format = nullptr;
  Target *target = exe_ctx.GetTargetPtr();
  if (target) {
    if (show_unique) {
      frame_format = target->GetDebugger().GetFrameFormatUnique();
    } else {
      frame_format = target->GetDebugger().GetFrameFormat();
    }
  }
  if (frame_format && FormatEntity::Format(*frame_format, s, &m_sc, &exe_ctx,
                                           nullptr, nullptr, false, false)) {
    strm->PutCString(s.GetString());
  } else {
    Dump(strm, true, false);
    strm->EOL();
  }
}

void StackFrame::Dump(Stream *strm, bool show_frame_index,
                      bool show_fullpaths) {
  if (strm == nullptr)
    return;

  if (show_frame_index)
    strm->Printf("frame #%u: ", m_frame_index);
  ExecutionContext exe_ctx(shared_from_this());
  Target *target = exe_ctx.GetTargetPtr();
  strm->Printf("0x%0*" PRIx64 " ",
               target ? (target->GetArchitecture().GetAddressByteSize() * 2)
                      : 16,
               GetFrameCodeAddress().GetLoadAddress(target));
  GetSymbolContext(eSymbolContextEverything);
  const bool show_module = true;
  const bool show_inline = true;
  const bool show_function_arguments = true;
  const bool show_function_name = true;
  m_sc.DumpStopContext(strm, exe_ctx.GetBestExecutionContextScope(),
                       GetFrameCodeAddress(), show_fullpaths, show_module,
                       show_inline, show_function_arguments,
                       show_function_name);
}

void StackFrame::UpdateCurrentFrameFromPreviousFrame(StackFrame &prev_frame) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  assert(GetStackID() ==
         prev_frame.GetStackID()); // TODO: remove this after some testing
  m_variable_list_sp = prev_frame.m_variable_list_sp;
  m_variable_list_value_objects.Swap(prev_frame.m_variable_list_value_objects);
  if (!m_disassembly.GetString().empty()) {
    m_disassembly.Clear();
    m_disassembly.PutCString(prev_frame.m_disassembly.GetString());
  }
}

void StackFrame::UpdatePreviousFrameFromCurrentFrame(StackFrame &curr_frame) {
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  assert(GetStackID() ==
         curr_frame.GetStackID());     // TODO: remove this after some testing
  m_id.SetPC(curr_frame.m_id.GetPC()); // Update the Stack ID PC value
  assert(GetThread() == curr_frame.GetThread());
  m_frame_index = curr_frame.m_frame_index;
  m_concrete_frame_index = curr_frame.m_concrete_frame_index;
  m_reg_context_sp = curr_frame.m_reg_context_sp;
  m_frame_code_addr = curr_frame.m_frame_code_addr;
  assert(!m_sc.target_sp || !curr_frame.m_sc.target_sp ||
         m_sc.target_sp.get() == curr_frame.m_sc.target_sp.get());
  assert(!m_sc.module_sp || !curr_frame.m_sc.module_sp ||
         m_sc.module_sp.get() == curr_frame.m_sc.module_sp.get());
  assert(m_sc.comp_unit == nullptr || curr_frame.m_sc.comp_unit == nullptr ||
         m_sc.comp_unit == curr_frame.m_sc.comp_unit);
  assert(m_sc.function == nullptr || curr_frame.m_sc.function == nullptr ||
         m_sc.function == curr_frame.m_sc.function);
  m_sc = curr_frame.m_sc;
  m_flags.Clear(GOT_FRAME_BASE | eSymbolContextEverything);
  m_flags.Set(m_sc.GetResolvedMask());
  m_frame_base.Clear();
  m_frame_base_error.Clear();
}

bool StackFrame::HasCachedData() const {
  if (m_variable_list_sp)
    return true;
  if (m_variable_list_value_objects.GetSize() > 0)
    return true;
  if (!m_disassembly.GetString().empty())
    return true;
  return false;
}

bool StackFrame::GetStatus(Stream &strm, bool show_frame_info, bool show_source,
                           bool show_unique, const char *frame_marker) {
  if (show_frame_info) {
    strm.Indent();
    DumpUsingSettingsFormat(&strm, show_unique, frame_marker);
  }

  if (show_source) {
    ExecutionContext exe_ctx(shared_from_this());
    bool have_source = false, have_debuginfo = false;
    Debugger::StopDisassemblyType disasm_display =
        Debugger::eStopDisassemblyTypeNever;
    Target *target = exe_ctx.GetTargetPtr();
    if (target) {
      Debugger &debugger = target->GetDebugger();
      const uint32_t source_lines_before =
          debugger.GetStopSourceLineCount(true);
      const uint32_t source_lines_after =
          debugger.GetStopSourceLineCount(false);
      disasm_display = debugger.GetStopDisassemblyDisplay();

      GetSymbolContext(eSymbolContextCompUnit | eSymbolContextLineEntry);
      if (m_sc.comp_unit && m_sc.line_entry.IsValid()) {
        have_debuginfo = true;
        if (source_lines_before > 0 || source_lines_after > 0) {
          size_t num_lines =
              target->GetSourceManager().DisplaySourceLinesWithLineNumbers(
                  m_sc.line_entry.file, m_sc.line_entry.line,
                  m_sc.line_entry.column, source_lines_before,
                  source_lines_after, "->", &strm);
          if (num_lines != 0)
            have_source = true;
          // TODO: Give here a one time warning if source file is missing.
        }
      }
      switch (disasm_display) {
      case Debugger::eStopDisassemblyTypeNever:
        break;

      case Debugger::eStopDisassemblyTypeNoDebugInfo:
        if (have_debuginfo)
          break;
        LLVM_FALLTHROUGH;

      case Debugger::eStopDisassemblyTypeNoSource:
        if (have_source)
          break;
        LLVM_FALLTHROUGH;

      case Debugger::eStopDisassemblyTypeAlways:
        if (target) {
          const uint32_t disasm_lines = debugger.GetDisassemblyLineCount();
          if (disasm_lines > 0) {
            const ArchSpec &target_arch = target->GetArchitecture();
            AddressRange pc_range;
            pc_range.GetBaseAddress() = GetFrameCodeAddress();
            pc_range.SetByteSize(disasm_lines *
                                 target_arch.GetMaximumOpcodeByteSize());
            const char *plugin_name = nullptr;
            const char *flavor = nullptr;
            const bool mixed_source_and_assembly = false;
            Disassembler::Disassemble(
                target->GetDebugger(), target_arch, plugin_name, flavor,
                exe_ctx, pc_range, disasm_lines, mixed_source_and_assembly, 0,
                Disassembler::eOptionMarkPCAddress, strm);
          }
        }
        break;
      }
    }
  }
  return true;
}

RecognizedStackFrameSP StackFrame::GetRecognizedFrame() {
  if (!m_recognized_frame_sp) {
    m_recognized_frame_sp =
        StackFrameRecognizerManager::RecognizeFrame(CalculateStackFrame());
  }
  return m_recognized_frame_sp;
}