CommandObjectExpression.cpp revision 341825 
1//===-- CommandObjectExpression.cpp -----------------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10// C Includes
11// C++ Includes
12// Other libraries and framework includes
13#include "llvm/ADT/STLExtras.h"
14#include "llvm/ADT/StringRef.h"
15
16// Project includes
17#include "CommandObjectExpression.h"
18#include "Plugins/ExpressionParser/Clang/ClangExpressionVariable.h"
19#include "lldb/Core/Debugger.h"
20#include "lldb/Core/Value.h"
21#include "lldb/Core/ValueObjectVariable.h"
22#include "lldb/DataFormatters/ValueObjectPrinter.h"
23#include "lldb/Expression/DWARFExpression.h"
24#include "lldb/Expression/REPL.h"
25#include "lldb/Expression/UserExpression.h"
26#include "lldb/Host/Host.h"
27#include "lldb/Host/OptionParser.h"
28#include "lldb/Interpreter/CommandInterpreter.h"
29#include "lldb/Interpreter/CommandReturnObject.h"
30#include "lldb/Interpreter/OptionArgParser.h"
31#include "lldb/Symbol/ObjectFile.h"
32#include "lldb/Symbol/Variable.h"
33#include "lldb/Target/Language.h"
34#include "lldb/Target/Process.h"
35#include "lldb/Target/StackFrame.h"
36#include "lldb/Target/Target.h"
37#include "lldb/Target/Thread.h"
38
39using namespace lldb;
40using namespace lldb_private;
41
42CommandObjectExpression::CommandOptions::CommandOptions() : OptionGroup() {}
43
44CommandObjectExpression::CommandOptions::~CommandOptions() = default;
45
46static OptionEnumValueElement g_description_verbosity_type[] = {
47    {eLanguageRuntimeDescriptionDisplayVerbosityCompact, "compact",
48     "Only show the description string"},
49    {eLanguageRuntimeDescriptionDisplayVerbosityFull, "full",
50     "Show the full output, including persistent variable's name and type"},
51    {0, nullptr, nullptr}};
52
53static OptionDefinition g_expression_options[] = {
54    // clang-format off
55  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "all-threads",           'a', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeBoolean,              "Should we run all threads if the execution doesn't complete on one thread."},
56  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "ignore-breakpoints",    'i', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeBoolean,              "Ignore breakpoint hits while running expressions"},
57  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "timeout",               't', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeUnsignedInteger,      "Timeout value (in microseconds) for running the expression."},
58  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "unwind-on-error",       'u', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeBoolean,              "Clean up program state if the expression causes a crash, or raises a signal.  "
59                                                                                                                                                                                  "Note, unlike gdb hitting a breakpoint is controlled by another option (-i)."},
60  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "debug",                 'g', OptionParser::eNoArgument,       nullptr, nullptr,                      0, eArgTypeNone,                 "When specified, debug the JIT code by setting a breakpoint on the first instruction "
61                                                                                                                                                                                  "and forcing breakpoints to not be ignored (-i0) and no unwinding to happen on error (-u0)."},
62  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "language",              'l', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeLanguage,             "Specifies the Language to use when parsing the expression.  If not set the target.language "
63                                                                                                                                                                                  "setting is used." },
64  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "apply-fixits",          'X', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeLanguage,             "If true, simple fix-it hints will be automatically applied to the expression." },
65  {LLDB_OPT_SET_1,                  false, "description-verbosity", 'v', OptionParser::eOptionalArgument, nullptr, g_description_verbosity_type, 0, eArgTypeDescriptionVerbosity, "How verbose should the output of this expression be, if the object description is asked for."},
66  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "top-level",             'p', OptionParser::eNoArgument,       nullptr, nullptr,                      0, eArgTypeNone,                 "Interpret the expression as a complete translation unit, without injecting it into the local "
67                                                                                                                                                                                  "context.  Allows declaration of persistent, top-level entities without a $ prefix."},
68  {LLDB_OPT_SET_1 | LLDB_OPT_SET_2, false, "allow-jit",             'j', OptionParser::eRequiredArgument, nullptr, nullptr,                      0, eArgTypeBoolean,              "Controls whether the expression can fall back to being JITted if it's not supported by "
69                                                                                                                                                                                  "the interpreter (defaults to true)."}
70    // clang-format on
71};
72
73Status CommandObjectExpression::CommandOptions::SetOptionValue(
74    uint32_t option_idx, llvm::StringRef option_arg,
75    ExecutionContext *execution_context) {
76  Status error;
77
78  const int short_option = GetDefinitions()[option_idx].short_option;
79
80  switch (short_option) {
81  case 'l':
82    language = Language::GetLanguageTypeFromString(option_arg);
83    if (language == eLanguageTypeUnknown)
84      error.SetErrorStringWithFormat(
85          "unknown language type: '%s' for expression",
86          option_arg.str().c_str());
87    break;
88
89  case 'a': {
90    bool success;
91    bool result;
92    result = OptionArgParser::ToBoolean(option_arg, true, &success);
93    if (!success)
94      error.SetErrorStringWithFormat(
95          "invalid all-threads value setting: \"%s\"",
96          option_arg.str().c_str());
97    else
98      try_all_threads = result;
99  } break;
100
101  case 'i': {
102    bool success;
103    bool tmp_value = OptionArgParser::ToBoolean(option_arg, true, &success);
104    if (success)
105      ignore_breakpoints = tmp_value;
106    else
107      error.SetErrorStringWithFormat(
108          "could not convert \"%s\" to a boolean value.",
109          option_arg.str().c_str());
110    break;
111  }
112
113  case 'j': {
114    bool success;
115    bool tmp_value = OptionArgParser::ToBoolean(option_arg, true, &success);
116    if (success)
117      allow_jit = tmp_value;
118    else
119      error.SetErrorStringWithFormat(
120          "could not convert \"%s\" to a boolean value.",
121          option_arg.str().c_str());
122    break;
123  }
124
125  case 't':
126    if (option_arg.getAsInteger(0, timeout)) {
127      timeout = 0;
128      error.SetErrorStringWithFormat("invalid timeout setting \"%s\"",
129                                     option_arg.str().c_str());
130    }
131    break;
132
133  case 'u': {
134    bool success;
135    bool tmp_value = OptionArgParser::ToBoolean(option_arg, true, &success);
136    if (success)
137      unwind_on_error = tmp_value;
138    else
139      error.SetErrorStringWithFormat(
140          "could not convert \"%s\" to a boolean value.",
141          option_arg.str().c_str());
142    break;
143  }
144
145  case 'v':
146    if (option_arg.empty()) {
147      m_verbosity = eLanguageRuntimeDescriptionDisplayVerbosityFull;
148      break;
149    }
150    m_verbosity = (LanguageRuntimeDescriptionDisplayVerbosity)
151        OptionArgParser::ToOptionEnum(
152            option_arg, GetDefinitions()[option_idx].enum_values, 0, error);
153    if (!error.Success())
154      error.SetErrorStringWithFormat(
155          "unrecognized value for description-verbosity '%s'",
156          option_arg.str().c_str());
157    break;
158
159  case 'g':
160    debug = true;
161    unwind_on_error = false;
162    ignore_breakpoints = false;
163    break;
164
165  case 'p':
166    top_level = true;
167    break;
168
169  case 'X': {
170    bool success;
171    bool tmp_value = OptionArgParser::ToBoolean(option_arg, true, &success);
172    if (success)
173      auto_apply_fixits = tmp_value ? eLazyBoolYes : eLazyBoolNo;
174    else
175      error.SetErrorStringWithFormat(
176          "could not convert \"%s\" to a boolean value.",
177          option_arg.str().c_str());
178    break;
179  }
180
181  default:
182    error.SetErrorStringWithFormat("invalid short option character '%c'",
183                                   short_option);
184    break;
185  }
186
187  return error;
188}
189
190void CommandObjectExpression::CommandOptions::OptionParsingStarting(
191    ExecutionContext *execution_context) {
192  auto process_sp =
193      execution_context ? execution_context->GetProcessSP() : ProcessSP();
194  if (process_sp) {
195    ignore_breakpoints = process_sp->GetIgnoreBreakpointsInExpressions();
196    unwind_on_error = process_sp->GetUnwindOnErrorInExpressions();
197  } else {
198    ignore_breakpoints = true;
199    unwind_on_error = true;
200  }
201
202  show_summary = true;
203  try_all_threads = true;
204  timeout = 0;
205  debug = false;
206  language = eLanguageTypeUnknown;
207  m_verbosity = eLanguageRuntimeDescriptionDisplayVerbosityCompact;
208  auto_apply_fixits = eLazyBoolCalculate;
209  top_level = false;
210  allow_jit = true;
211}
212
213llvm::ArrayRef<OptionDefinition>
214CommandObjectExpression::CommandOptions::GetDefinitions() {
215  return llvm::makeArrayRef(g_expression_options);
216}
217
218CommandObjectExpression::CommandObjectExpression(
219    CommandInterpreter &interpreter)
220    : CommandObjectRaw(
221          interpreter, "expression", "Evaluate an expression on the current "
222                                     "thread.  Displays any returned value "
223                                     "with LLDB's default formatting.",
224          "", eCommandProcessMustBePaused | eCommandTryTargetAPILock),
225      IOHandlerDelegate(IOHandlerDelegate::Completion::Expression),
226      m_option_group(), m_format_options(eFormatDefault),
227      m_repl_option(LLDB_OPT_SET_1, false, "repl", 'r', "Drop into REPL", false,
228                    true),
229      m_command_options(), m_expr_line_count(0), m_expr_lines() {
230  SetHelpLong(
231      R"(
232Single and multi-line expressions:
233
234)"
235      "    The expression provided on the command line must be a complete expression \
236with no newlines.  To evaluate a multi-line expression, \
237hit a return after an empty expression, and lldb will enter the multi-line expression editor. \
238Hit return on an empty line to end the multi-line expression."
239
240      R"(
241
242Timeouts:
243
244)"
245      "    If the expression can be evaluated statically (without running code) then it will be.  \
246Otherwise, by default the expression will run on the current thread with a short timeout: \
247currently .25 seconds.  If it doesn't return in that time, the evaluation will be interrupted \
248and resumed with all threads running.  You can use the -a option to disable retrying on all \
249threads.  You can use the -t option to set a shorter timeout."
250      R"(
251
252User defined variables:
253
254)"
255      "    You can define your own variables for convenience or to be used in subsequent expressions.  \
256You define them the same way you would define variables in C.  If the first character of \
257your user defined variable is a $, then the variable's value will be available in future \
258expressions, otherwise it will just be available in the current expression."
259      R"(
260
261Continuing evaluation after a breakpoint:
262
263)"
264      "    If the \"-i false\" option is used, and execution is interrupted by a breakpoint hit, once \
265you are done with your investigation, you can either remove the expression execution frames \
266from the stack with \"thread return -x\" or if you are still interested in the expression result \
267you can issue the \"continue\" command and the expression evaluation will complete and the \
268expression result will be available using the \"thread.completed-expression\" key in the thread \
269format."
270
271      R"(
272
273Examples:
274
275    expr my_struct->a = my_array[3]
276    expr -f bin -- (index * 8) + 5
277    expr unsigned int $foo = 5
278    expr char c[] = \"foo\"; c[0])");
279
280  CommandArgumentEntry arg;
281  CommandArgumentData expression_arg;
282
283  // Define the first (and only) variant of this arg.
284  expression_arg.arg_type = eArgTypeExpression;
285  expression_arg.arg_repetition = eArgRepeatPlain;
286
287  // There is only one variant this argument could be; put it into the argument
288  // entry.
289  arg.push_back(expression_arg);
290
291  // Push the data for the first argument into the m_arguments vector.
292  m_arguments.push_back(arg);
293
294  // Add the "--format" and "--gdb-format"
295  m_option_group.Append(&m_format_options,
296                        OptionGroupFormat::OPTION_GROUP_FORMAT |
297                            OptionGroupFormat::OPTION_GROUP_GDB_FMT,
298                        LLDB_OPT_SET_1);
299  m_option_group.Append(&m_command_options);
300  m_option_group.Append(&m_varobj_options, LLDB_OPT_SET_ALL,
301                        LLDB_OPT_SET_1 | LLDB_OPT_SET_2);
302  m_option_group.Append(&m_repl_option, LLDB_OPT_SET_ALL, LLDB_OPT_SET_3);
303  m_option_group.Finalize();
304}
305
306CommandObjectExpression::~CommandObjectExpression() = default;
307
308Options *CommandObjectExpression::GetOptions() { return &m_option_group; }
309
310static lldb_private::Status
311CanBeUsedForElementCountPrinting(ValueObject &valobj) {
312  CompilerType type(valobj.GetCompilerType());
313  CompilerType pointee;
314  if (!type.IsPointerType(&pointee))
315    return Status("as it does not refer to a pointer");
316  if (pointee.IsVoidType())
317    return Status("as it refers to a pointer to void");
318  return Status();
319}
320
321bool CommandObjectExpression::EvaluateExpression(llvm::StringRef expr,
322                                                 Stream *output_stream,
323                                                 Stream *error_stream,
324                                                 CommandReturnObject *result) {
325  // Don't use m_exe_ctx as this might be called asynchronously after the
326  // command object DoExecute has finished when doing multi-line expression
327  // that use an input reader...
328  ExecutionContext exe_ctx(m_interpreter.GetExecutionContext());
329
330  Target *target = exe_ctx.GetTargetPtr();
331
332  if (!target)
333    target = GetDummyTarget();
334
335  if (target) {
336    lldb::ValueObjectSP result_valobj_sp;
337    bool keep_in_memory = true;
338    StackFrame *frame = exe_ctx.GetFramePtr();
339
340    EvaluateExpressionOptions options;
341    options.SetCoerceToId(m_varobj_options.use_objc);
342    options.SetUnwindOnError(m_command_options.unwind_on_error);
343    options.SetIgnoreBreakpoints(m_command_options.ignore_breakpoints);
344    options.SetKeepInMemory(keep_in_memory);
345    options.SetUseDynamic(m_varobj_options.use_dynamic);
346    options.SetTryAllThreads(m_command_options.try_all_threads);
347    options.SetDebug(m_command_options.debug);
348    options.SetLanguage(m_command_options.language);
349    options.SetExecutionPolicy(
350        m_command_options.allow_jit
351            ? EvaluateExpressionOptions::default_execution_policy
352            : lldb_private::eExecutionPolicyNever);
353
354    bool auto_apply_fixits;
355    if (m_command_options.auto_apply_fixits == eLazyBoolCalculate)
356      auto_apply_fixits = target->GetEnableAutoApplyFixIts();
357    else
358      auto_apply_fixits =
359          m_command_options.auto_apply_fixits == eLazyBoolYes ? true : false;
360
361    options.SetAutoApplyFixIts(auto_apply_fixits);
362
363    if (m_command_options.top_level)
364      options.SetExecutionPolicy(eExecutionPolicyTopLevel);
365
366    // If there is any chance we are going to stop and want to see what went
367    // wrong with our expression, we should generate debug info
368    if (!m_command_options.ignore_breakpoints ||
369        !m_command_options.unwind_on_error)
370      options.SetGenerateDebugInfo(true);
371
372    if (m_command_options.timeout > 0)
373      options.SetTimeout(std::chrono::microseconds(m_command_options.timeout));
374    else
375      options.SetTimeout(llvm::None);
376
377    ExpressionResults success = target->EvaluateExpression(
378        expr, frame, result_valobj_sp, options, &m_fixed_expression);
379
380    // We only tell you about the FixIt if we applied it.  The compiler errors
381    // will suggest the FixIt if it parsed.
382    if (error_stream && !m_fixed_expression.empty() &&
383        target->GetEnableNotifyAboutFixIts()) {
384      if (success == eExpressionCompleted)
385        error_stream->Printf(
386            "  Fix-it applied, fixed expression was: \n    %s\n",
387            m_fixed_expression.c_str());
388    }
389
390    if (result_valobj_sp) {
391      Format format = m_format_options.GetFormat();
392
393      if (result_valobj_sp->GetError().Success()) {
394        if (format != eFormatVoid) {
395          if (format != eFormatDefault)
396            result_valobj_sp->SetFormat(format);
397
398          if (m_varobj_options.elem_count > 0) {
399            Status error(CanBeUsedForElementCountPrinting(*result_valobj_sp));
400            if (error.Fail()) {
401              result->AppendErrorWithFormat(
402                  "expression cannot be used with --element-count %s\n",
403                  error.AsCString(""));
404              result->SetStatus(eReturnStatusFailed);
405              return false;
406            }
407          }
408
409          DumpValueObjectOptions options(m_varobj_options.GetAsDumpOptions(
410              m_command_options.m_verbosity, format));
411          options.SetVariableFormatDisplayLanguage(
412              result_valobj_sp->GetPreferredDisplayLanguage());
413
414          result_valobj_sp->Dump(*output_stream, options);
415
416          if (result)
417            result->SetStatus(eReturnStatusSuccessFinishResult);
418        }
419      } else {
420        if (result_valobj_sp->GetError().GetError() ==
421            UserExpression::kNoResult) {
422          if (format != eFormatVoid &&
423              m_interpreter.GetDebugger().GetNotifyVoid()) {
424            error_stream->PutCString("(void)\n");
425          }
426
427          if (result)
428            result->SetStatus(eReturnStatusSuccessFinishResult);
429        } else {
430          const char *error_cstr = result_valobj_sp->GetError().AsCString();
431          if (error_cstr && error_cstr[0]) {
432            const size_t error_cstr_len = strlen(error_cstr);
433            const bool ends_with_newline =
434                error_cstr[error_cstr_len - 1] == '\n';
435            if (strstr(error_cstr, "error:") != error_cstr)
436              error_stream->PutCString("error: ");
437            error_stream->Write(error_cstr, error_cstr_len);
438            if (!ends_with_newline)
439              error_stream->EOL();
440          } else {
441            error_stream->PutCString("error: unknown error\n");
442          }
443
444          if (result)
445            result->SetStatus(eReturnStatusFailed);
446        }
447      }
448    }
449  } else {
450    error_stream->Printf("error: invalid execution context for expression\n");
451    return false;
452  }
453
454  return true;
455}
456
457void CommandObjectExpression::IOHandlerInputComplete(IOHandler &io_handler,
458                                                     std::string &line) {
459  io_handler.SetIsDone(true);
460  //    StreamSP output_stream =
461  //    io_handler.GetDebugger().GetAsyncOutputStream();
462  //    StreamSP error_stream = io_handler.GetDebugger().GetAsyncErrorStream();
463  StreamFileSP output_sp(io_handler.GetOutputStreamFile());
464  StreamFileSP error_sp(io_handler.GetErrorStreamFile());
465
466  EvaluateExpression(line.c_str(), output_sp.get(), error_sp.get());
467  if (output_sp)
468    output_sp->Flush();
469  if (error_sp)
470    error_sp->Flush();
471}
472
473bool CommandObjectExpression::IOHandlerIsInputComplete(IOHandler &io_handler,
474                                                       StringList &lines) {
475  // An empty lines is used to indicate the end of input
476  const size_t num_lines = lines.GetSize();
477  if (num_lines > 0 && lines[num_lines - 1].empty()) {
478    // Remove the last empty line from "lines" so it doesn't appear in our
479    // resulting input and return true to indicate we are done getting lines
480    lines.PopBack();
481    return true;
482  }
483  return false;
484}
485
486void CommandObjectExpression::GetMultilineExpression() {
487  m_expr_lines.clear();
488  m_expr_line_count = 0;
489
490  Debugger &debugger = GetCommandInterpreter().GetDebugger();
491  bool color_prompt = debugger.GetUseColor();
492  const bool multiple_lines = true; // Get multiple lines
493  IOHandlerSP io_handler_sp(
494      new IOHandlerEditline(debugger, IOHandler::Type::Expression,
495                            "lldb-expr", // Name of input reader for history
496                            llvm::StringRef(), // No prompt
497                            llvm::StringRef(), // Continuation prompt
498                            multiple_lines, color_prompt,
499                            1, // Show line numbers starting at 1
500                            *this));
501
502  StreamFileSP output_sp(io_handler_sp->GetOutputStreamFile());
503  if (output_sp) {
504    output_sp->PutCString(
505        "Enter expressions, then terminate with an empty line to evaluate:\n");
506    output_sp->Flush();
507  }
508  debugger.PushIOHandler(io_handler_sp);
509}
510
511bool CommandObjectExpression::DoExecute(llvm::StringRef command,
512                                        CommandReturnObject &result) {
513  m_fixed_expression.clear();
514  auto exe_ctx = GetCommandInterpreter().GetExecutionContext();
515  m_option_group.NotifyOptionParsingStarting(&exe_ctx);
516
517  if (command.empty()) {
518    GetMultilineExpression();
519    return result.Succeeded();
520  }
521
522  OptionsWithRaw args(command);
523  llvm::StringRef expr = args.GetRawPart();
524
525  if (args.HasArgs()) {
526    if (!ParseOptionsAndNotify(args.GetArgs(), result, m_option_group, exe_ctx))
527      return false;
528
529    if (m_repl_option.GetOptionValue().GetCurrentValue()) {
530      Target *target = m_interpreter.GetExecutionContext().GetTargetPtr();
531      if (target) {
532        // Drop into REPL
533        m_expr_lines.clear();
534        m_expr_line_count = 0;
535
536        Debugger &debugger = target->GetDebugger();
537
538        // Check if the LLDB command interpreter is sitting on top of a REPL
539        // that launched it...
540        if (debugger.CheckTopIOHandlerTypes(IOHandler::Type::CommandInterpreter,
541                                            IOHandler::Type::REPL)) {
542          // the LLDB command interpreter is sitting on top of a REPL that
543          // launched it, so just say the command interpreter is done and
544          // fall back to the existing REPL
545          m_interpreter.GetIOHandler(false)->SetIsDone(true);
546        } else {
547          // We are launching the REPL on top of the current LLDB command
548          // interpreter, so just push one
549          bool initialize = false;
550          Status repl_error;
551          REPLSP repl_sp(target->GetREPL(repl_error, m_command_options.language,
552                                         nullptr, false));
553
554          if (!repl_sp) {
555            initialize = true;
556            repl_sp = target->GetREPL(repl_error, m_command_options.language,
557                                      nullptr, true);
558            if (!repl_error.Success()) {
559              result.SetError(repl_error);
560              return result.Succeeded();
561            }
562          }
563
564          if (repl_sp) {
565            if (initialize) {
566              repl_sp->SetCommandOptions(m_command_options);
567              repl_sp->SetFormatOptions(m_format_options);
568              repl_sp->SetValueObjectDisplayOptions(m_varobj_options);
569            }
570
571            IOHandlerSP io_handler_sp(repl_sp->GetIOHandler());
572
573            io_handler_sp->SetIsDone(false);
574
575            debugger.PushIOHandler(io_handler_sp);
576          } else {
577            repl_error.SetErrorStringWithFormat(
578                "Couldn't create a REPL for %s",
579                Language::GetNameForLanguageType(m_command_options.language));
580            result.SetError(repl_error);
581            return result.Succeeded();
582          }
583        }
584      }
585    }
586    // No expression following options
587    else if (expr.empty()) {
588      GetMultilineExpression();
589      return result.Succeeded();
590    }
591  }
592
593  Target *target = GetSelectedOrDummyTarget();
594  if (EvaluateExpression(expr, &(result.GetOutputStream()),
595                         &(result.GetErrorStream()), &result)) {
596
597    if (!m_fixed_expression.empty() && target->GetEnableNotifyAboutFixIts()) {
598      CommandHistory &history = m_interpreter.GetCommandHistory();
599      // FIXME: Can we figure out what the user actually typed (e.g. some alias
600      // for expr???)
601      // If we can it would be nice to show that.
602      std::string fixed_command("expression ");
603      if (args.HasArgs()) {
604        // Add in any options that might have been in the original command:
605        fixed_command.append(args.GetArgStringWithDelimiter());
606        fixed_command.append(m_fixed_expression);
607      } else
608        fixed_command.append(m_fixed_expression);
609      history.AppendString(fixed_command);
610    }
611    // Increment statistics to record this expression evaluation success.
612    target->IncrementStats(StatisticKind::ExpressionSuccessful);
613    return true;
614  }
615
616  // Increment statistics to record this expression evaluation failure.
617  target->IncrementStats(StatisticKind::ExpressionFailure);
618  result.SetStatus(eReturnStatusFailed);
619  return false;
620}
621