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

[Pavel Labath via lldb-commits]

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@@ -0,0 +1,308 @@
+//===-- DILParser.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
+//
+// This implements the recursive descent parser for the Data Inspection
+// Language (DIL), and its helper functions, which will eventually underlie the
+// 'frame variable' command. The language that this parser recognizes is
+// described in lldb/docs/dil-expr-lang.ebnf
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/ValueObject/DILParser.h"
+#include "lldb/Target/ExecutionContextScope.h"
+#include "lldb/ValueObject/DILAST.h"
+#include "lldb/ValueObject/DILEval.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/FormatAdapters.h"
+#include <limits.h>
+#include <memory>
+#include <sstream>
+#include <stdlib.h>
+#include <string>
+
+namespace lldb_private::dil {
+
+inline void TokenKindsJoinImpl(std::ostringstream &os, Token::Kind k) {
+  os << "'" << Token::GetTokenName(k).str() << "'";
+}
+
+template <typename... Ts>
+inline void TokenKindsJoinImpl(std::ostringstream &os, Token::Kind k,
+                               Ts... ks) {
+  TokenKindsJoinImpl(os, k);
+  os << ", ";
+  TokenKindsJoinImpl(os, ks...);
+}
+
+template <typename... Ts>
+inline std::string TokenKindsJoin(Token::Kind k, Ts... ks) {
+  std::ostringstream os;
+  TokenKindsJoinImpl(os, k, ks...);
+
+  return os.str();
+}
+
+std::string FormatDiagnostics(llvm::StringRef text, const std::string &message,
+                              uint32_t loc) {
+  // Get the source buffer and the location of the current token.
+  size_t loc_offset = (size_t)loc;
+
+  // Look for the start of the line.
+  size_t line_start = text.rfind('\n', loc_offset);
+  line_start = line_start == llvm::StringRef::npos ? 0 : line_start + 1;
+
+  // Look for the end of the line.
+  size_t line_end = text.find('\n', loc_offset);
+  line_end = line_end == llvm::StringRef::npos ? text.size() : line_end;
+
+  // Get a view of the current line in the source code and the position of the
+  // diagnostics pointer.
+  llvm::StringRef line = text.slice(line_start, line_end);
+  int32_t arrow = loc + 1; // Column offset starts at 1, not 0.
+
+  // Calculate the padding in case we point outside of the expression (this can
+  // happen if the parser expected something, but got EOF).˚
+  size_t expr_rpad = std::max(0, arrow - static_cast<int32_t>(line.size()));
+  size_t arrow_rpad = std::max(0, static_cast<int32_t>(line.size()) - arrow);
+
+  return llvm::formatv("<expr:1:{0}>: {1}\n{2}\n{3}", loc, message,
+                       llvm::fmt_pad(line, 0, expr_rpad),
+                       llvm::fmt_pad("^", arrow - 1, arrow_rpad));
+}
+
+DILParser::DILParser(llvm::StringRef dil_input_expr, DILLexer lexer,
+                     std::shared_ptr<ExecutionContextScope> exe_ctx_scope,
+                     lldb::DynamicValueType use_dynamic, bool use_synthetic,
+                     bool fragile_ivar, bool check_ptr_vs_member)
+    : m_ctx_scope(exe_ctx_scope), m_input_expr(dil_input_expr),
+      m_dil_lexer(lexer), m_dil_token(lexer.GetCurrentToken()),
+      m_use_dynamic(use_dynamic), m_use_synthetic(use_synthetic),
+      m_fragile_ivar(fragile_ivar), m_check_ptr_vs_member(check_ptr_vs_member) {
+}
+
+llvm::Expected<DILASTNodeUP> DILParser::Run() {
+  DILASTNodeUP expr;
+
+  expr = ParseExpression();
+
+  Expect(Token::Kind::eof);
+
+  if (m_error.Fail())
+    return m_error.ToError();
+
+  return expr;
+}
+
+// Parse an expression.
+//
+//  expression:
+//    primary_expression
+//
+DILASTNodeUP DILParser::ParseExpression() { return ParsePrimaryExpression(); }
+
+// Parse a primary_expression.
+//
+//  primary_expression:
+//    id_expression
+//    "this"
+//    "(" expression ")"
+//
+DILASTNodeUP DILParser::ParsePrimaryExpression() {
+  if (m_dil_token.IsOneOf(Token::coloncolon, Token::identifier)) {
+    // Save the source location for the diagnostics message.
+    uint32_t loc = m_dil_token.GetLocation();
+    auto identifier = ParseIdExpression();
+
+    return std::make_unique<IdentifierNode>(loc, identifier, m_use_dynamic,
+                                            m_ctx_scope);
+  } else if (m_dil_token.Is(Token::l_paren)) {
+    ConsumeToken();
+    auto expr = ParseExpression();
+    Expect(Token::r_paren);
+    ConsumeToken();
+    return expr;
+  }
+
+  BailOut(ErrorCode::kInvalidExpressionSyntax,
+          llvm::formatv("Unexpected token: {0}", TokenDescription(m_dil_token)),
+          m_dil_token.GetLocation());
+  return std::make_unique<ErrorNode>();
+}
+
+// Parse nested_name_specifier.
+//
+//  nested_name_specifier:
+//    type_name "::"
+//    namespace_name "::"
+//    nested_name_specifier identifier "::"
+//
+std::string DILParser::ParseNestedNameSpecifier() {
+  // The first token in nested_name_specifier is always an identifier, or
+  // '(anonymous namespace)'.
+  if (m_dil_token.IsNot(Token::identifier) &&
+      m_dil_token.IsNot(Token::l_paren)) {
+    return "";
+  }
+
+  // Anonymous namespaces need to be treated specially: They are represented
+  // the the string '(anonymous namespace)', which has a space in it (throwing
+  // off normal parsing) and is not actually proper C++> Check to see if we're
+  // looking at '(anonymous namespace)::...'
+  if (m_dil_token.Is(Token::l_paren)) {
+    // Look for all the pieces, in order:
+    // l_paren 'anonymous' 'namespace' r_paren coloncolon
+    if (m_dil_lexer.LookAhead(1).Is(Token::identifier) &&
+        (m_dil_lexer.LookAhead(1).GetSpelling() == "anonymous") &&
+        m_dil_lexer.LookAhead(2).Is(Token::identifier) &&
+        (m_dil_lexer.LookAhead(2).GetSpelling() == "namespace") &&
+        m_dil_lexer.LookAhead(3).Is(Token::r_paren) &&
+        m_dil_lexer.LookAhead(4).Is(Token::coloncolon)) {
+      m_dil_lexer.Advance(4);
+      m_dil_token = m_dil_lexer.GetCurrentToken();
+
+      assert((m_dil_token.Is(Token::identifier) ||
+              m_dil_token.Is(Token::l_paren)) &&
+             "Expected an identifier or anonymous namespace, but not found.");
+      // Continue parsing the nested_namespace_specifier.
+      std::string identifier2 = ParseNestedNameSpecifier();
+      if (identifier2.empty()) {
+        Expect(Token::identifier);
+        identifier2 = m_dil_token.GetSpelling();
+        ConsumeToken();
+      }
+      return "(anonymous namespace)::" + identifier2;
+    }
+
+    return "";
+  } // end of special handling for '(anonymous namespace)'
+
+  // If the next token is scope ("::"), then this is indeed a
+  // nested_name_specifier
+  if (m_dil_lexer.LookAhead(1).Is(Token::coloncolon)) {
+    // This nested_name_specifier is a single identifier.
+    std::string identifier = m_dil_token.GetSpelling();
+    m_dil_lexer.Advance(1);
+    m_dil_token = m_dil_lexer.GetCurrentToken();
+    Expect(Token::coloncolon);
+    ConsumeToken();
+    // Continue parsing the nested_name_specifier.
+    return identifier + "::" + ParseNestedNameSpecifier();
+  }
+
+  return "";
+}
+
+// Parse an id_expression.
+//
+//  id_expression:
+//    unqualified_id
+//    qualified_id
+//
+//  qualified_id:
+//    ["::"] [nested_name_specifier] unqualified_id
+//    ["::"] identifier
+//
+//  identifier:
+//    ? Token::identifier ?
+//
+std::string DILParser::ParseIdExpression() {
+  // Try parsing optional global scope operator.
+  bool global_scope = false;
+  if (m_dil_token.Is(Token::coloncolon)) {
+    global_scope = true;
+    ConsumeToken();
+  }
+
+  // Try parsing optional nested_name_specifier.
+  auto nested_name_specifier = ParseNestedNameSpecifier();
+
+  // If nested_name_specifier is present, then it's qualified_id production.
+  // Follow the first production rule.
+  if (!nested_name_specifier.empty()) {
+    // Parse unqualified_id and construct a fully qualified id expression.
+    auto unqualified_id = ParseUnqualifiedId();
+
+    return llvm::formatv("{0}{1}{2}", global_scope ? "::" : "",
+                         nested_name_specifier, unqualified_id);
+  }
+
+  // No nested_name_specifier, but with global scope -- this is also a
+  // qualified_id production. Follow the second production rule.
+  else if (global_scope) {
+    Expect(Token::identifier);
+    std::string identifier = m_dil_token.GetSpelling();
+    ConsumeToken();
+    return llvm::formatv("{0}{1}", global_scope ? "::" : "", identifier);
+  }
+
+  // This is unqualified_id production.
+  return ParseUnqualifiedId();
+}
+
+// Parse an unqualified_id.
+//
+//  unqualified_id:
+//    identifier
+//
+//  identifier:
+//    ? Token::identifier ?
+//
+std::string DILParser::ParseUnqualifiedId() {
+  Expect(Token::identifier);
+  std::string identifier = m_dil_token.GetSpelling();
+  ConsumeToken();
+  return identifier;
+}
+
+void DILParser::BailOut(ErrorCode code, const std::string &error,
+                        uint32_t loc) {
+  if (m_error.Fail()) {
+    // If error is already set, then the parser is in the "bail-out" mode. Don't
+    // do anything and keep the original error.
+    return;
+  }
+
+  m_error = Status((uint32_t)code, lldb::eErrorTypeGeneric,
+                   FormatDiagnostics(m_input_expr, error, loc));
+  m_dil_token = Token(Token::eof, "", 0);
+}
+
+void DILParser::BailOut(Status error) {
+  if (m_error.Fail()) {
+    // If error is already set, then the parser is in the "bail-out" mode. Don't
+    // do anything and keep the original error.
+    return;
+  }
+  m_error = std::move(error);
+  m_dil_token = Token(Token::eof, "", 0);
+}
+
+void DILParser::ConsumeToken() {
----------------
labath wrote:

I would like to get rid of this function. Checking for eof is not necessary now that the lexer generates EOFs ad infinitum. And instead of maintaining a copy of the "current" token, I think it'd be better to always just get the current token from the lexer.

I'd be totally fine with renaming `GetCurrentToken` into something shorter so that it's not tedious to write (`m_lexer.Current()` ?), and I am also fine with putting the token into a local variable in functions which do some elaborate checking on in. I'd just like to avoid it being a global variable that needs to be kept up to date.

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