path: root/include/lldb/Expression/UserExpression.h

//===-- UserExpression.h ----------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef liblldb_UserExpression_h_
#define liblldb_UserExpression_h_

// C Includes
// C++ Includes
#include <memory>
#include <string>
#include <vector>

// Other libraries and framework includes
// Project includes
#include "lldb/Core/Address.h"
#include "lldb/Expression/Expression.h"
#include "lldb/Expression/Materializer.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Target.h"
#include "lldb/lldb-forward.h"
#include "lldb/lldb-private.h"

namespace lldb_private {

//----------------------------------------------------------------------
/// @class UserExpression UserExpression.h "lldb/Expression/UserExpression.h"
/// @brief Encapsulates a one-time expression for use in lldb.
///
/// LLDB uses expressions for various purposes, notably to call functions
/// and as a backend for the expr command.  UserExpression is a virtual base
/// class that encapsulates the objects needed to parse and interpret or
/// JIT an expression.  The actual parsing part will be provided by the specific
/// implementations of UserExpression - which will be vended through the
/// appropriate TypeSystem.
//----------------------------------------------------------------------
class UserExpression : public Expression {
public:
  enum { kDefaultTimeout = 500000u };

  //------------------------------------------------------------------
  /// Constructor
  ///
  /// @param[in] expr
  ///     The expression to parse.
  ///
  /// @param[in] expr_prefix
  ///     If non-nullptr, a C string containing translation-unit level
  ///     definitions to be included when the expression is parsed.
  ///
  /// @param[in] language
  ///     If not eLanguageTypeUnknown, a language to use when parsing
  ///     the expression.  Currently restricted to those languages
  ///     supported by Clang.
  ///
  /// @param[in] desired_type
  ///     If not eResultTypeAny, the type to use for the expression
  ///     result.
  //------------------------------------------------------------------
  UserExpression(ExecutionContextScope &exe_scope, llvm::StringRef expr,
                 llvm::StringRef prefix, lldb::LanguageType language,
                 ResultType desired_type,
                 const EvaluateExpressionOptions &options);

  //------------------------------------------------------------------
  /// Destructor
  //------------------------------------------------------------------
  ~UserExpression() override;

  //------------------------------------------------------------------
  /// Parse the expression
  ///
  /// @param[in] diagnostic_manager
  ///     A diagnostic manager to report parse errors and warnings to.
  ///
  /// @param[in] exe_ctx
  ///     The execution context to use when looking up entities that
  ///     are needed for parsing (locations of functions, types of
  ///     variables, persistent variables, etc.)
  ///
  /// @param[in] execution_policy
  ///     Determines whether interpretation is possible or mandatory.
  ///
  /// @param[in] keep_result_in_memory
  ///     True if the resulting persistent variable should reside in
  ///     target memory, if applicable.
  ///
  /// @return
  ///     True on success (no errors); false otherwise.
  //------------------------------------------------------------------
  virtual bool Parse(DiagnosticManager &diagnostic_manager,
                     ExecutionContext &exe_ctx,
                     lldb_private::ExecutionPolicy execution_policy,
                     bool keep_result_in_memory, bool generate_debug_info) = 0;

  virtual bool CanInterpret() = 0;

  bool MatchesContext(ExecutionContext &exe_ctx);

  //------------------------------------------------------------------
  /// Execute the parsed expression by callinng the derived class's
  /// DoExecute method.
  ///
  /// @param[in] diagnostic_manager
  ///     A diagnostic manager to report errors to.
  ///
  /// @param[in] exe_ctx
  ///     The execution context to use when looking up entities that
  ///     are needed for parsing (locations of variables, etc.)
  ///
  /// @param[in] options
  ///     Expression evaluation options.
  ///
  /// @param[in] shared_ptr_to_me
  ///     This is a shared pointer to this UserExpression.  This is
  ///     needed because Execute can push a thread plan that will hold onto
  ///     the UserExpression for an unbounded period of time.  So you
  ///     need to give the thread plan a reference to this object that can
  ///     keep it alive.
  ///
  /// @param[in] result
  ///     A pointer to direct at the persistent variable in which the
  ///     expression's result is stored.
  ///
  /// @return
  ///     A Process::Execution results value.
  //------------------------------------------------------------------
  lldb::ExpressionResults Execute(DiagnosticManager &diagnostic_manager,
                                  ExecutionContext &exe_ctx,
                                  const EvaluateExpressionOptions &options,
                                  lldb::UserExpressionSP &shared_ptr_to_me,
                                  lldb::ExpressionVariableSP &result);

  //------------------------------------------------------------------
  /// Apply the side effects of the function to program state.
  ///
  /// @param[in] diagnostic_manager
  ///     A diagnostic manager to report errors to.
  ///
  /// @param[in] exe_ctx
  ///     The execution context to use when looking up entities that
  ///     are needed for parsing (locations of variables, etc.)
  ///
  /// @param[in] result
  ///     A pointer to direct at the persistent variable in which the
  ///     expression's result is stored.
  ///
  /// @param[in] function_stack_pointer
  ///     A pointer to the base of the function's stack frame.  This
  ///     is used to determine whether the expression result resides in
  ///     memory that will still be valid, or whether it needs to be
  ///     treated as homeless for the purpose of future expressions.
  ///
  /// @return
  ///     A Process::Execution results value.
  //------------------------------------------------------------------
  virtual bool FinalizeJITExecution(
      DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
      lldb::ExpressionVariableSP &result,
      lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
      lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) = 0;

  //------------------------------------------------------------------
  /// Return the string that the parser should parse.
  //------------------------------------------------------------------
  const char *Text() override { return m_expr_text.c_str(); }

  //------------------------------------------------------------------
  /// Return the string that the user typed.
  //------------------------------------------------------------------
  const char *GetUserText() { return m_expr_text.c_str(); }

  //------------------------------------------------------------------
  /// Return the function name that should be used for executing the
  /// expression.  Text() should contain the definition of this
  /// function.
  //------------------------------------------------------------------
  const char *FunctionName() override { return "$__lldb_expr"; }

  //------------------------------------------------------------------
  /// Return the language that should be used when parsing.  To use
  /// the default, return eLanguageTypeUnknown.
  //------------------------------------------------------------------
  lldb::LanguageType Language() override { return m_language; }

  //------------------------------------------------------------------
  /// Return the desired result type of the function, or
  /// eResultTypeAny if indifferent.
  //------------------------------------------------------------------
  ResultType DesiredResultType() override { return m_desired_type; }

  //------------------------------------------------------------------
  /// Return true if validation code should be inserted into the
  /// expression.
  //------------------------------------------------------------------
  bool NeedsValidation() override { return true; }

  //------------------------------------------------------------------
  /// Return true if external variables in the expression should be
  /// resolved.
  //------------------------------------------------------------------
  bool NeedsVariableResolution() override { return true; }

  EvaluateExpressionOptions *GetOptions() override { return &m_options; }

  virtual lldb::ExpressionVariableSP
  GetResultAfterDematerialization(ExecutionContextScope *exe_scope) {
    return lldb::ExpressionVariableSP();
  }

  virtual lldb::ModuleSP GetJITModule() { return lldb::ModuleSP(); }

  //------------------------------------------------------------------
  /// Evaluate one expression in the scratch context of the
  /// target passed in the exe_ctx and return its result.
  ///
  /// @param[in] exe_ctx
  ///     The execution context to use when evaluating the expression.
  ///
  /// @param[in] options
  ///     Expression evaluation options.  N.B. The language in the
  ///     evaluation options will be used to determine the language used for
  ///     expression evaluation.
  ///
  /// @param[in] expr_cstr
  ///     A C string containing the expression to be evaluated.
  ///
  /// @param[in] expr_prefix
  ///     If non-nullptr, a C string containing translation-unit level
  ///     definitions to be included when the expression is parsed.
  ///
  /// @param[in,out] result_valobj_sp
  ///      If execution is successful, the result valobj is placed here.
  ///
  /// @param[out] error
  ///     Filled in with an error in case the expression evaluation
  ///     fails to parse, run, or evaluated.
  ///
  /// @param[in] line_offset
  ///     The offset of the first line of the expression from the "beginning" of
  ///     a virtual source file used for error reporting and debug info.
  ///
  /// @param[out] fixed_expression
  ///     If non-nullptr, the fixed expression is copied into the provided
  ///     string.
  ///
  /// @param[out] jit_module_sp_ptr
  ///     If non-nullptr, used to persist the generated IR module.
  ///
  /// @result
  ///      A Process::ExpressionResults value.  eExpressionCompleted for
  ///      success.
  //------------------------------------------------------------------
  static lldb::ExpressionResults
  Evaluate(ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
           llvm::StringRef expr_cstr, llvm::StringRef expr_prefix,
           lldb::ValueObjectSP &result_valobj_sp, Error &error,
           uint32_t line_offset = 0, std::string *fixed_expression = nullptr,
           lldb::ModuleSP *jit_module_sp_ptr = nullptr);

  static const Error::ValueType kNoResult =
      0x1001; ///< ValueObject::GetError() returns this if there is no result
              ///from the expression.

  const char *GetFixedText() {
    if (m_fixed_text.empty())
      return nullptr;
    return m_fixed_text.c_str();
  }

protected:
  virtual lldb::ExpressionResults
  DoExecute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
            const EvaluateExpressionOptions &options,
            lldb::UserExpressionSP &shared_ptr_to_me,
            lldb::ExpressionVariableSP &result) = 0;

  static lldb::addr_t GetObjectPointer(lldb::StackFrameSP frame_sp,
                                       ConstString &object_name, Error &err);

  //------------------------------------------------------------------
  /// Populate m_in_cplusplus_method and m_in_objectivec_method based on the
  /// environment.
  //------------------------------------------------------------------

  void InstallContext(ExecutionContext &exe_ctx);

  bool LockAndCheckContext(ExecutionContext &exe_ctx, lldb::TargetSP &target_sp,
                           lldb::ProcessSP &process_sp,
                           lldb::StackFrameSP &frame_sp);

  Address m_address;       ///< The address the process is stopped in.
  std::string m_expr_text; ///< The text of the expression, as typed by the user
  std::string m_expr_prefix; ///< The text of the translation-level definitions,
                             ///as provided by the user
  std::string m_fixed_text; ///< The text of the expression with fix-its applied
                            ///- this won't be set if the fixed text doesn't
                            ///parse.
  lldb::LanguageType m_language; ///< The language to use when parsing
                                 ///(eLanguageTypeUnknown means use defaults)
  ResultType m_desired_type; ///< The type to coerce the expression's result to.
                             ///If eResultTypeAny, inferred from the expression.
  EvaluateExpressionOptions
      m_options; ///< Additional options provided by the user.
};

} // namespace lldb_private

#endif // liblldb_UserExpression_h_