lldb/source/ValueObject/DILEval.cpp

//===-- DILEval.cpp -------------------------------------------------------===//
//
// 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/ValueObject/DILEval.h"
#include "lldb/Symbol/VariableList.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/ValueObject/DILAST.h"
#include "lldb/ValueObject/ValueObject.h"
#include "lldb/ValueObject/ValueObjectRegister.h"
#include "lldb/ValueObject/ValueObjectVariable.h"
#include "llvm/Support/FormatAdapters.h"
#include <memory>

namespace lldb_private::dil {

static lldb::ValueObjectSP LookupStaticIdentifier(
    VariableList &variable_list, std::shared_ptr<StackFrame> exe_scope,
    llvm::StringRef name_ref, llvm::StringRef unqualified_name) {
  // First look for an exact match to the (possibly) qualified name.
  for (const lldb::VariableSP &var_sp : variable_list) {
    lldb::ValueObjectSP valobj_sp(
        ValueObjectVariable::Create(exe_scope.get(), var_sp));
    if (valobj_sp && valobj_sp->GetVariable() &&
        (valobj_sp->GetVariable()->NameMatches(ConstString(name_ref))))
      return valobj_sp;
  }

  // If the qualified name is the same as the unqualfied name, there's nothing
  // more to be done.
  if (name_ref == unqualified_name)
    return nullptr;

  // We didn't match the qualified name; try to match the unqualified name.
  for (const lldb::VariableSP &var_sp : variable_list) {
    lldb::ValueObjectSP valobj_sp(
        ValueObjectVariable::Create(exe_scope.get(), var_sp));
    if (valobj_sp && valobj_sp->GetVariable() &&
        (valobj_sp->GetVariable()->NameMatches(ConstString(unqualified_name))))
      return valobj_sp;
  }

  return nullptr;
}

static lldb::VariableSP DILFindVariable(ConstString name,
                                        lldb::VariableListSP variable_list) {
  lldb::VariableSP exact_match;
  std::vector<lldb::VariableSP> possible_matches;

  for (lldb::VariableSP var_sp : *variable_list) {
    llvm::StringRef str_ref_name = var_sp->GetName().GetStringRef();
    // Check for global vars, which might start with '::'.
    str_ref_name.consume_front("::");

    if (str_ref_name == name.GetStringRef())
      possible_matches.push_back(var_sp);
    else if (var_sp->NameMatches(name))
      possible_matches.push_back(var_sp);
  }

  // Look for exact matches (favors local vars over global vars)
  auto exact_match_it =
      llvm::find_if(possible_matches, [&](lldb::VariableSP var_sp) {
        return var_sp->GetName() == name;
      });

  if (exact_match_it != possible_matches.end())
    return *exact_match_it;

  // Look for a global var exact match.
  for (auto var_sp : possible_matches) {
    llvm::StringRef str_ref_name = var_sp->GetName().GetStringRef();
    str_ref_name.consume_front("::");
    if (str_ref_name == name.GetStringRef())
      return var_sp;
  }

  // If there's a single non-exact match, take it.
  if (possible_matches.size() == 1)
    return possible_matches[0];

  return nullptr;
}

lldb::ValueObjectSP LookupGlobalIdentifier(
    llvm::StringRef name_ref, std::shared_ptr<StackFrame> stack_frame,
    lldb::TargetSP target_sp, lldb::DynamicValueType use_dynamic,
    CompilerType *scope_ptr) {
  // First look for match in "local" global variables.
  lldb::VariableListSP variable_list(stack_frame->GetInScopeVariableList(true));
  name_ref.consume_front("::");

  lldb::ValueObjectSP value_sp;
  if (variable_list) {
    lldb::VariableSP var_sp =
        DILFindVariable(ConstString(name_ref), variable_list);
    if (var_sp)
      value_sp =
          stack_frame->GetValueObjectForFrameVariable(var_sp, use_dynamic);
  }

  if (value_sp)
    return value_sp;

  // Also check for static global vars.
  if (variable_list) {
    const char *type_name = "";
    if (scope_ptr)
      type_name = scope_ptr->GetCanonicalType().GetTypeName().AsCString();
    std::string name_with_type_prefix =
        llvm::formatv("{0}::{1}", type_name, name_ref).str();
    value_sp = LookupStaticIdentifier(*variable_list, stack_frame,
                                      name_with_type_prefix, name_ref);
    if (!value_sp)
      value_sp = LookupStaticIdentifier(*variable_list, stack_frame, name_ref,
                                        name_ref);
  }

  if (value_sp)
    return value_sp;

  // Check for match in modules global variables.
  VariableList modules_var_list;
  target_sp->GetImages().FindGlobalVariables(
      ConstString(name_ref), std::numeric_limits<uint32_t>::max(),
      modules_var_list);
  if (modules_var_list.Empty())
    return nullptr;

  for (const lldb::VariableSP &var_sp : modules_var_list) {
    std::string qualified_name = llvm::formatv("::{0}", name_ref).str();
    if (var_sp->NameMatches(ConstString(name_ref)) ||
        var_sp->NameMatches(ConstString(qualified_name))) {
      value_sp = ValueObjectVariable::Create(stack_frame.get(), var_sp);
      break;
    }
  }

  if (value_sp)
    return value_sp;

  return nullptr;
}

lldb::ValueObjectSP LookupIdentifier(llvm::StringRef name_ref,
                                     std::shared_ptr<StackFrame> stack_frame,
                                     lldb::DynamicValueType use_dynamic,
                                     CompilerType *scope_ptr) {
  // Support $rax as a special syntax for accessing registers.
  // Will return an invalid value in case the requested register doesn't exist.
  if (name_ref.consume_front("$")) {
    lldb::RegisterContextSP reg_ctx(stack_frame->GetRegisterContext());
    if (!reg_ctx)
      return nullptr;

    if (const RegisterInfo *reg_info = reg_ctx->GetRegisterInfoByName(name_ref))
      return ValueObjectRegister::Create(stack_frame.get(), reg_ctx, reg_info);

    return nullptr;
  }

  lldb::VariableListSP variable_list(
      stack_frame->GetInScopeVariableList(false));

  if (!name_ref.contains("::")) {
    if (!scope_ptr || !scope_ptr->IsValid()) {
      // Lookup in the current frame.
      // Try looking for a local variable in current scope.
      lldb::ValueObjectSP value_sp;
      if (variable_list) {
        lldb::VariableSP var_sp =
            DILFindVariable(ConstString(name_ref), variable_list);
        if (var_sp)
          value_sp =
              stack_frame->GetValueObjectForFrameVariable(var_sp, use_dynamic);
      }
      if (!value_sp)
        value_sp = stack_frame->FindVariable(ConstString(name_ref));

      if (value_sp)
        return value_sp;

      // Try looking for an instance variable (class member).
      SymbolContext sc = stack_frame->GetSymbolContext(
          lldb::eSymbolContextFunction | lldb::eSymbolContextBlock);
      llvm::StringRef ivar_name = sc.GetInstanceVariableName();
      value_sp = stack_frame->FindVariable(ConstString(ivar_name));
      if (value_sp)
        value_sp = value_sp->GetChildMemberWithName(name_ref);

      if (value_sp)
        return value_sp;
    }
  }
  return nullptr;
}

Interpreter::Interpreter(lldb::TargetSP target, llvm::StringRef expr,
                         lldb::DynamicValueType use_dynamic,
                         std::shared_ptr<StackFrame> frame_sp)
    : m_target(std::move(target)), m_expr(expr), m_default_dynamic(use_dynamic),
      m_exe_ctx_scope(frame_sp) {}

llvm::Expected<lldb::ValueObjectSP> Interpreter::Evaluate(const ASTNode *node) {
  // Evaluate an AST.
  auto value_or_error = node->Accept(this);
  // Return the computed value-or-error. The caller is responsible for
  // checking if an error occured during the evaluation.
  return value_or_error;
}

llvm::Expected<lldb::ValueObjectSP>
Interpreter::Visit(const IdentifierNode *node) {
  lldb::DynamicValueType use_dynamic = m_default_dynamic;

  lldb::ValueObjectSP identifier =
      LookupIdentifier(node->GetName(), m_exe_ctx_scope, use_dynamic);

  if (!identifier)
    identifier = LookupGlobalIdentifier(node->GetName(), m_exe_ctx_scope,
                                        m_target, use_dynamic);
  if (!identifier) {
    std::string errMsg =
        llvm::formatv("use of undeclared identifier '{0}'", node->GetName());
    return llvm::make_error<DILDiagnosticError>(
        m_expr, errMsg, node->GetLocation(), node->GetName().size());
  }

  return identifier;
}

llvm::Expected<lldb::ValueObjectSP>
Interpreter::Visit(const UnaryOpNode *node) {
  Status error;
  auto rhs_or_err = Evaluate(node->operand());
  if (!rhs_or_err)
    return rhs_or_err;

  lldb::ValueObjectSP rhs = *rhs_or_err;

  switch (node->kind()) {
  case UnaryOpKind::Deref: {
    lldb::ValueObjectSP dynamic_rhs = rhs->GetDynamicValue(m_default_dynamic);
    if (dynamic_rhs)
      rhs = dynamic_rhs;

    lldb::ValueObjectSP child_sp = rhs->Dereference(error);
    if (error.Fail())
      return llvm::make_error<DILDiagnosticError>(m_expr, error.AsCString(),
                                                  node->GetLocation());

    return child_sp;
  }
  case UnaryOpKind::AddrOf: {
    Status error;
    lldb::ValueObjectSP value = rhs->AddressOf(error);
    if (error.Fail())
      return llvm::make_error<DILDiagnosticError>(m_expr, error.AsCString(),
                                                  node->GetLocation());

    return value;
  }
  }

  // Unsupported/invalid operation.
  return llvm::make_error<DILDiagnosticError>(
      m_expr, "invalid ast: unexpected binary operator", node->GetLocation());
}

} // namespace lldb_private::dil