[Lldb-commits] [lldb] [LLDB] Add DIL code for handling plain variable names. (PR #120971)

[Pavel Labath via lldb-commits]

================
@@ -0,0 +1,273 @@
+//===-- 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;
+
+  typedef std::vector<lldb::VariableSP> collection;
+  typedef collection::iterator iterator;
+
+  iterator pos, end = variable_list->end();
+  for (pos = variable_list->begin(); pos != end; ++pos) {
+    llvm::StringRef str_ref_name = pos->get()->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(*pos);
+    else if (pos->get()->NameMatches(name))
+      possible_matches.push_back(*pos);
+  }
+
+  // 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())
+    exact_match = *exact_match_it;
+
+  if (!exact_match)
+    // 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()) {
+        exact_match = var_sp;
+        break;
+      }
+    }
+
+  if (!exact_match && possible_matches.size() == 1)
+    exact_match = possible_matches[0];
+
+  return exact_match;
+}
+
+std::unique_ptr<IdentifierInfo> 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 IdentifierInfo::FromValue(*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 IdentifierInfo::FromValue(*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 IdentifierInfo::FromValue(*value_sp);
+
+  return nullptr;
+}
+
+std::unique_ptr<IdentifierInfo>
+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::ValueObjectSP value_sp;
+
+    lldb::RegisterContextSP reg_ctx(stack_frame->GetRegisterContext());
+    if (!reg_ctx)
+      return nullptr;
+
+    if (const RegisterInfo *reg_info = reg_ctx->GetRegisterInfoByName(name_ref))
+      value_sp =
+          ValueObjectRegister::Create(stack_frame.get(), reg_ctx, reg_info);
+
+    if (value_sp)
+      return IdentifierInfo::FromValue(*value_sp);
+
+    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 IdentifierInfo::FromValue(*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 IdentifierInfo::FromValue(*(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::DILEvalNode(const ASTNode *node) {
+
+  // Traverse an AST pointed by the `node`.
+  auto value_or_error = node->Accept(this);
+
+  // Return the computed value or error.
+  return value_or_error;
+}
+
+llvm::Expected<lldb::ValueObjectSP>
+Interpreter::Visit(const IdentifierNode *node) {
+  lldb::DynamicValueType use_dynamic = node->GetUseDynamic();
+
+  std::unique_ptr<IdentifierInfo> 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;
+    std::string name = node->GetName();
+    errMsg = llvm::formatv("use of undeclared identifier '{0}'", name);
+    Status error = Status(
+        (uint32_t)ErrorCode::kUndeclaredIdentifier, lldb::eErrorTypeGeneric,
+        FormatDiagnostics(m_expr, errMsg, node->GetLocation()));
+    return error.ToError();
+  }
+  lldb::ValueObjectSP val;
+  lldb::TargetSP target_sp;
+  Status error;
+
+  assert(identifier->GetKind() == IdentifierInfo::Kind::eValue &&
+         "Unrecognized identifier kind");
+
+  val = identifier->GetValue();
+
+  if (val->GetCompilerType().IsReferenceType()) {
+    Status error;
+    val = val->Dereference(error);
+    if (error.Fail())
+      return error.ToError();
+  }
----------------
labath wrote:

I don't think we actually want this (here). If the user accesses a reference type, we should show them that they're accessing a reference. Can you compare the behavior of this implementation with/without this block with the current implementation of "frame variable"? Which one is a better match?

https://github.com/llvm/llvm-project/pull/120971