xref: /llvm-project/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp (revision b852fb1ec5fa15f0b913cc4988cbd09239b19904)
1 //===-- ClangUserExpression.cpp -------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include <cstdio>
10 #include <sys/types.h>
11 
12 #include <cstdlib>
13 #include <map>
14 #include <string>
15 
16 #include "ClangUserExpression.h"
17 
18 #include "ASTResultSynthesizer.h"
19 #include "ClangASTMetadata.h"
20 #include "ClangDiagnostic.h"
21 #include "ClangExpressionDeclMap.h"
22 #include "ClangExpressionParser.h"
23 #include "ClangModulesDeclVendor.h"
24 #include "ClangPersistentVariables.h"
25 #include "CppModuleConfiguration.h"
26 
27 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
28 #include "lldb/Core/Debugger.h"
29 #include "lldb/Core/Module.h"
30 #include "lldb/Expression/ExpressionSourceCode.h"
31 #include "lldb/Expression/IRExecutionUnit.h"
32 #include "lldb/Expression/IRInterpreter.h"
33 #include "lldb/Expression/Materializer.h"
34 #include "lldb/Host/HostInfo.h"
35 #include "lldb/Symbol/Block.h"
36 #include "lldb/Symbol/CompileUnit.h"
37 #include "lldb/Symbol/Function.h"
38 #include "lldb/Symbol/ObjectFile.h"
39 #include "lldb/Symbol/SymbolFile.h"
40 #include "lldb/Symbol/SymbolVendor.h"
41 #include "lldb/Symbol/Type.h"
42 #include "lldb/Symbol/VariableList.h"
43 #include "lldb/Target/ExecutionContext.h"
44 #include "lldb/Target/Process.h"
45 #include "lldb/Target/StackFrame.h"
46 #include "lldb/Target/Target.h"
47 #include "lldb/Target/ThreadPlan.h"
48 #include "lldb/Target/ThreadPlanCallUserExpression.h"
49 #include "lldb/Utility/ConstString.h"
50 #include "lldb/Utility/LLDBLog.h"
51 #include "lldb/Utility/Log.h"
52 #include "lldb/Utility/StreamString.h"
53 #include "lldb/ValueObject/ValueObjectConstResult.h"
54 
55 #include "clang/AST/DeclCXX.h"
56 #include "clang/AST/DeclObjC.h"
57 
58 #include "llvm/ADT/ScopeExit.h"
59 #include "llvm/BinaryFormat/Dwarf.h"
60 
61 using namespace lldb_private;
62 
63 char ClangUserExpression::ID;
64 
65 ClangUserExpression::ClangUserExpression(
66     ExecutionContextScope &exe_scope, llvm::StringRef expr,
67     llvm::StringRef prefix, SourceLanguage language, ResultType desired_type,
68     const EvaluateExpressionOptions &options, ValueObject *ctx_obj)
69     : LLVMUserExpression(exe_scope, expr, prefix, language, desired_type,
70                          options),
71       m_type_system_helper(*m_target_wp.lock(), options.GetExecutionPolicy() ==
72                                                     eExecutionPolicyTopLevel),
73       m_result_delegate(exe_scope.CalculateTarget()), m_ctx_obj(ctx_obj) {
74   switch (m_language.name) {
75   case llvm::dwarf::DW_LNAME_C_plus_plus:
76     m_allow_cxx = true;
77     break;
78   case llvm::dwarf::DW_LNAME_ObjC:
79     m_allow_objc = true;
80     break;
81   case llvm::dwarf::DW_LNAME_ObjC_plus_plus:
82   default:
83     m_allow_cxx = true;
84     m_allow_objc = true;
85     break;
86   }
87 }
88 
89 ClangUserExpression::~ClangUserExpression() = default;
90 
91 void ClangUserExpression::ScanContext(ExecutionContext &exe_ctx, Status &err) {
92   Log *log = GetLog(LLDBLog::Expressions);
93 
94   LLDB_LOGF(log, "ClangUserExpression::ScanContext()");
95 
96   m_target = exe_ctx.GetTargetPtr();
97 
98   if (!(m_allow_cxx || m_allow_objc)) {
99     LLDB_LOGF(log, "  [CUE::SC] Settings inhibit C++ and Objective-C");
100     return;
101   }
102 
103   StackFrame *frame = exe_ctx.GetFramePtr();
104   if (frame == nullptr) {
105     LLDB_LOGF(log, "  [CUE::SC] Null stack frame");
106     return;
107   }
108 
109   SymbolContext sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
110                                                   lldb::eSymbolContextBlock);
111 
112   if (!sym_ctx.function) {
113     LLDB_LOGF(log, "  [CUE::SC] Null function");
114     return;
115   }
116 
117   // Find the block that defines the function represented by "sym_ctx"
118   Block *function_block = sym_ctx.GetFunctionBlock();
119 
120   if (!function_block) {
121     LLDB_LOGF(log, "  [CUE::SC] Null function block");
122     return;
123   }
124 
125   CompilerDeclContext decl_context = function_block->GetDeclContext();
126 
127   if (!decl_context) {
128     LLDB_LOGF(log, "  [CUE::SC] Null decl context");
129     return;
130   }
131 
132   if (m_ctx_obj) {
133     switch (m_ctx_obj->GetObjectRuntimeLanguage()) {
134     case lldb::eLanguageTypeC:
135     case lldb::eLanguageTypeC89:
136     case lldb::eLanguageTypeC99:
137     case lldb::eLanguageTypeC11:
138     case lldb::eLanguageTypeC_plus_plus:
139     case lldb::eLanguageTypeC_plus_plus_03:
140     case lldb::eLanguageTypeC_plus_plus_11:
141     case lldb::eLanguageTypeC_plus_plus_14:
142       m_in_cplusplus_method = true;
143       break;
144     case lldb::eLanguageTypeObjC:
145     case lldb::eLanguageTypeObjC_plus_plus:
146       m_in_objectivec_method = true;
147       break;
148     default:
149       break;
150     }
151     m_needs_object_ptr = true;
152   } else if (clang::CXXMethodDecl *method_decl =
153           TypeSystemClang::DeclContextGetAsCXXMethodDecl(decl_context)) {
154     if (m_allow_cxx && method_decl->isInstance()) {
155       if (m_enforce_valid_object) {
156         lldb::VariableListSP variable_list_sp(
157             function_block->GetBlockVariableList(true));
158 
159         const char *thisErrorString = "Stopped in a C++ method, but 'this' "
160                                       "isn't available; pretending we are in a "
161                                       "generic context";
162 
163         if (!variable_list_sp) {
164           err = Status::FromErrorString(thisErrorString);
165           return;
166         }
167 
168         lldb::VariableSP this_var_sp(
169             variable_list_sp->FindVariable(ConstString("this")));
170 
171         if (!this_var_sp || !this_var_sp->IsInScope(frame) ||
172             !this_var_sp->LocationIsValidForFrame(frame)) {
173           err = Status::FromErrorString(thisErrorString);
174           return;
175         }
176       }
177 
178       m_in_cplusplus_method = true;
179       m_needs_object_ptr = true;
180     }
181   } else if (clang::ObjCMethodDecl *method_decl =
182                  TypeSystemClang::DeclContextGetAsObjCMethodDecl(
183                      decl_context)) {
184     if (m_allow_objc) {
185       if (m_enforce_valid_object) {
186         lldb::VariableListSP variable_list_sp(
187             function_block->GetBlockVariableList(true));
188 
189         const char *selfErrorString = "Stopped in an Objective-C method, but "
190                                       "'self' isn't available; pretending we "
191                                       "are in a generic context";
192 
193         if (!variable_list_sp) {
194           err = Status::FromErrorString(selfErrorString);
195           return;
196         }
197 
198         lldb::VariableSP self_variable_sp =
199             variable_list_sp->FindVariable(ConstString("self"));
200 
201         if (!self_variable_sp || !self_variable_sp->IsInScope(frame) ||
202             !self_variable_sp->LocationIsValidForFrame(frame)) {
203           err = Status::FromErrorString(selfErrorString);
204           return;
205         }
206       }
207 
208       m_in_objectivec_method = true;
209       m_needs_object_ptr = true;
210 
211       if (!method_decl->isInstanceMethod())
212         m_in_static_method = true;
213     }
214   } else if (clang::FunctionDecl *function_decl =
215                  TypeSystemClang::DeclContextGetAsFunctionDecl(decl_context)) {
216     // We might also have a function that said in the debug information that it
217     // captured an object pointer.  The best way to deal with getting to the
218     // ivars at present is by pretending that this is a method of a class in
219     // whatever runtime the debug info says the object pointer belongs to.  Do
220     // that here.
221 
222     if (std::optional<ClangASTMetadata> metadata =
223             TypeSystemClang::DeclContextGetMetaData(decl_context,
224                                                     function_decl);
225         metadata && metadata->HasObjectPtr()) {
226       lldb::LanguageType language = metadata->GetObjectPtrLanguage();
227       if (language == lldb::eLanguageTypeC_plus_plus) {
228         if (m_enforce_valid_object) {
229           lldb::VariableListSP variable_list_sp(
230               function_block->GetBlockVariableList(true));
231 
232           const char *thisErrorString = "Stopped in a context claiming to "
233                                         "capture a C++ object pointer, but "
234                                         "'this' isn't available; pretending we "
235                                         "are in a generic context";
236 
237           if (!variable_list_sp) {
238             err = Status::FromErrorString(thisErrorString);
239             return;
240           }
241 
242           lldb::VariableSP this_var_sp(
243               variable_list_sp->FindVariable(ConstString("this")));
244 
245           if (!this_var_sp || !this_var_sp->IsInScope(frame) ||
246               !this_var_sp->LocationIsValidForFrame(frame)) {
247             err = Status::FromErrorString(thisErrorString);
248             return;
249           }
250         }
251 
252         m_in_cplusplus_method = true;
253         m_needs_object_ptr = true;
254       } else if (language == lldb::eLanguageTypeObjC) {
255         if (m_enforce_valid_object) {
256           lldb::VariableListSP variable_list_sp(
257               function_block->GetBlockVariableList(true));
258 
259           const char *selfErrorString =
260               "Stopped in a context claiming to capture an Objective-C object "
261               "pointer, but 'self' isn't available; pretending we are in a "
262               "generic context";
263 
264           if (!variable_list_sp) {
265             err = Status::FromErrorString(selfErrorString);
266             return;
267           }
268 
269           lldb::VariableSP self_variable_sp =
270               variable_list_sp->FindVariable(ConstString("self"));
271 
272           if (!self_variable_sp || !self_variable_sp->IsInScope(frame) ||
273               !self_variable_sp->LocationIsValidForFrame(frame)) {
274             err = Status::FromErrorString(selfErrorString);
275             return;
276           }
277 
278           Type *self_type = self_variable_sp->GetType();
279 
280           if (!self_type) {
281             err = Status::FromErrorString(selfErrorString);
282             return;
283           }
284 
285           CompilerType self_clang_type = self_type->GetForwardCompilerType();
286 
287           if (!self_clang_type) {
288             err = Status::FromErrorString(selfErrorString);
289             return;
290           }
291 
292           if (TypeSystemClang::IsObjCClassType(self_clang_type)) {
293             return;
294           } else if (TypeSystemClang::IsObjCObjectPointerType(
295                          self_clang_type)) {
296             m_in_objectivec_method = true;
297             m_needs_object_ptr = true;
298           } else {
299             err = Status::FromErrorString(selfErrorString);
300             return;
301           }
302         } else {
303           m_in_objectivec_method = true;
304           m_needs_object_ptr = true;
305         }
306       }
307     }
308   }
309 }
310 
311 // This is a really nasty hack, meant to fix Objective-C expressions of the
312 // form (int)[myArray count].  Right now, because the type information for
313 // count is not available, [myArray count] returns id, which can't be directly
314 // cast to int without causing a clang error.
315 static void ApplyObjcCastHack(std::string &expr) {
316   const std::string from = "(int)[";
317   const std::string to = "(int)(long long)[";
318 
319   size_t offset;
320 
321   while ((offset = expr.find(from)) != expr.npos)
322     expr.replace(offset, from.size(), to);
323 }
324 
325 bool ClangUserExpression::SetupPersistentState(DiagnosticManager &diagnostic_manager,
326                                  ExecutionContext &exe_ctx) {
327   if (Target *target = exe_ctx.GetTargetPtr()) {
328     if (PersistentExpressionState *persistent_state =
329             target->GetPersistentExpressionStateForLanguage(
330                 lldb::eLanguageTypeC)) {
331       m_clang_state = llvm::cast<ClangPersistentVariables>(persistent_state);
332       m_result_delegate.RegisterPersistentState(persistent_state);
333     } else {
334       diagnostic_manager.PutString(
335           lldb::eSeverityError, "couldn't start parsing (no persistent data)");
336       return false;
337     }
338   } else {
339     diagnostic_manager.PutString(lldb::eSeverityError,
340                                  "error: couldn't start parsing (no target)");
341     return false;
342   }
343   return true;
344 }
345 
346 static void SetupDeclVendor(ExecutionContext &exe_ctx, Target *target,
347                             DiagnosticManager &diagnostic_manager) {
348   if (!target->GetEnableAutoImportClangModules())
349     return;
350 
351   auto *persistent_state = llvm::cast<ClangPersistentVariables>(
352       target->GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
353   if (!persistent_state)
354     return;
355 
356   std::shared_ptr<ClangModulesDeclVendor> decl_vendor =
357       persistent_state->GetClangModulesDeclVendor();
358   if (!decl_vendor)
359     return;
360 
361   StackFrame *frame = exe_ctx.GetFramePtr();
362   if (!frame)
363     return;
364 
365   Block *block = frame->GetFrameBlock();
366   if (!block)
367     return;
368   SymbolContext sc;
369 
370   block->CalculateSymbolContext(&sc);
371 
372   if (!sc.comp_unit)
373     return;
374   StreamString error_stream;
375 
376   ClangModulesDeclVendor::ModuleVector modules_for_macros =
377       persistent_state->GetHandLoadedClangModules();
378   if (decl_vendor->AddModulesForCompileUnit(*sc.comp_unit, modules_for_macros,
379                                             error_stream))
380     return;
381 
382   // Failed to load some modules, so emit the error stream as a diagnostic.
383   if (!error_stream.Empty()) {
384     // The error stream already contains several Clang diagnostics that might
385     // be either errors or warnings, so just print them all as one remark
386     // diagnostic to prevent that the message starts with "error: error:".
387     diagnostic_manager.PutString(lldb::eSeverityInfo, error_stream.GetString());
388     return;
389   }
390 
391   diagnostic_manager.PutString(lldb::eSeverityError,
392                                "Unknown error while loading modules needed for "
393                                "current compilation unit.");
394 }
395 
396 ClangExpressionSourceCode::WrapKind ClangUserExpression::GetWrapKind() const {
397   assert(m_options.GetExecutionPolicy() != eExecutionPolicyTopLevel &&
398          "Top level expressions aren't wrapped.");
399   using Kind = ClangExpressionSourceCode::WrapKind;
400   if (m_in_cplusplus_method)
401     return Kind::CppMemberFunction;
402   else if (m_in_objectivec_method) {
403     if (m_in_static_method)
404       return Kind::ObjCStaticMethod;
405     return Kind::ObjCInstanceMethod;
406   }
407   // Not in any kind of 'special' function, so just wrap it in a normal C
408   // function.
409   return Kind::Function;
410 }
411 
412 void ClangUserExpression::CreateSourceCode(
413     DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
414     std::vector<std::string> modules_to_import, bool for_completion) {
415 
416   std::string prefix = m_expr_prefix;
417 
418   if (m_options.GetExecutionPolicy() == eExecutionPolicyTopLevel) {
419     m_transformed_text = m_expr_text;
420   } else {
421     m_source_code.reset(ClangExpressionSourceCode::CreateWrapped(
422         m_filename, prefix, m_expr_text, GetWrapKind()));
423 
424     if (!m_source_code->GetText(m_transformed_text, exe_ctx, !m_ctx_obj,
425                                 for_completion, modules_to_import)) {
426       diagnostic_manager.PutString(lldb::eSeverityError,
427                                    "couldn't construct expression body");
428       return;
429     }
430 
431     // Find and store the start position of the original code inside the
432     // transformed code. We need this later for the code completion.
433     std::size_t original_start;
434     std::size_t original_end;
435     bool found_bounds = m_source_code->GetOriginalBodyBounds(
436         m_transformed_text, original_start, original_end);
437     if (found_bounds)
438       m_user_expression_start_pos = original_start;
439   }
440 }
441 
442 static bool SupportsCxxModuleImport(lldb::LanguageType language) {
443   switch (language) {
444   case lldb::eLanguageTypeC_plus_plus:
445   case lldb::eLanguageTypeC_plus_plus_03:
446   case lldb::eLanguageTypeC_plus_plus_11:
447   case lldb::eLanguageTypeC_plus_plus_14:
448   case lldb::eLanguageTypeObjC_plus_plus:
449     return true;
450   default:
451     return false;
452   }
453 }
454 
455 /// Utility method that puts a message into the expression log and
456 /// returns an invalid module configuration.
457 static CppModuleConfiguration LogConfigError(const std::string &msg) {
458   Log *log = GetLog(LLDBLog::Expressions);
459   LLDB_LOG(log, "[C++ module config] {0}", msg);
460   return CppModuleConfiguration();
461 }
462 
463 CppModuleConfiguration GetModuleConfig(lldb::LanguageType language,
464                                        ExecutionContext &exe_ctx) {
465   Log *log = GetLog(LLDBLog::Expressions);
466 
467   // Don't do anything if this is not a C++ module configuration.
468   if (!SupportsCxxModuleImport(language))
469     return LogConfigError("Language doesn't support C++ modules");
470 
471   Target *target = exe_ctx.GetTargetPtr();
472   if (!target)
473     return LogConfigError("No target");
474 
475   StackFrame *frame = exe_ctx.GetFramePtr();
476   if (!frame)
477     return LogConfigError("No frame");
478 
479   Block *block = frame->GetFrameBlock();
480   if (!block)
481     return LogConfigError("No block");
482 
483   SymbolContext sc;
484   block->CalculateSymbolContext(&sc);
485   if (!sc.comp_unit)
486     return LogConfigError("Couldn't calculate symbol context");
487 
488   // Build a list of files we need to analyze to build the configuration.
489   FileSpecList files;
490   for (auto &f : sc.comp_unit->GetSupportFiles())
491     files.AppendIfUnique(f->Materialize());
492   // We also need to look at external modules in the case of -gmodules as they
493   // contain the support files for libc++ and the C library.
494   llvm::DenseSet<SymbolFile *> visited_symbol_files;
495   sc.comp_unit->ForEachExternalModule(
496       visited_symbol_files, [&files](Module &module) {
497         for (std::size_t i = 0; i < module.GetNumCompileUnits(); ++i) {
498           const SupportFileList &support_files =
499               module.GetCompileUnitAtIndex(i)->GetSupportFiles();
500           for (auto &f : support_files) {
501             files.AppendIfUnique(f->Materialize());
502           }
503         }
504         return false;
505       });
506 
507   LLDB_LOG(log, "[C++ module config] Found {0} support files to analyze",
508            files.GetSize());
509   if (log && log->GetVerbose()) {
510     for (auto &f : files)
511       LLDB_LOGV(log, "[C++ module config] Analyzing support file: {0}",
512                 f.GetPath());
513   }
514 
515   // Try to create a configuration from the files. If there is no valid
516   // configuration possible with the files, this just returns an invalid
517   // configuration.
518   return CppModuleConfiguration(files, target->GetArchitecture().GetTriple());
519 }
520 
521 bool ClangUserExpression::PrepareForParsing(
522     DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
523     bool for_completion) {
524   InstallContext(exe_ctx);
525 
526   if (!SetupPersistentState(diagnostic_manager, exe_ctx))
527     return false;
528 
529   Status err;
530   ScanContext(exe_ctx, err);
531 
532   if (!err.Success()) {
533     diagnostic_manager.PutString(lldb::eSeverityWarning, err.AsCString());
534   }
535 
536   ////////////////////////////////////
537   // Generate the expression
538   //
539 
540   ApplyObjcCastHack(m_expr_text);
541 
542   SetupDeclVendor(exe_ctx, m_target, diagnostic_manager);
543 
544   m_filename = m_clang_state->GetNextExprFileName();
545 
546   if (m_target->GetImportStdModule() == eImportStdModuleTrue)
547     SetupCppModuleImports(exe_ctx);
548 
549   CreateSourceCode(diagnostic_manager, exe_ctx, m_imported_cpp_modules,
550                    for_completion);
551   return true;
552 }
553 
554 bool ClangUserExpression::TryParse(
555     DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
556     lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
557     bool generate_debug_info) {
558   m_materializer_up = std::make_unique<Materializer>();
559 
560   ResetDeclMap(exe_ctx, m_result_delegate, keep_result_in_memory);
561 
562   auto on_exit = llvm::make_scope_exit([this]() { ResetDeclMap(); });
563 
564   if (!DeclMap()->WillParse(exe_ctx, GetMaterializer())) {
565     diagnostic_manager.PutString(
566         lldb::eSeverityError,
567         "current process state is unsuitable for expression parsing");
568     return false;
569   }
570 
571   if (m_options.GetExecutionPolicy() == eExecutionPolicyTopLevel) {
572     DeclMap()->SetLookupsEnabled(true);
573   }
574 
575   m_parser = std::make_unique<ClangExpressionParser>(
576       exe_ctx.GetBestExecutionContextScope(), *this, generate_debug_info,
577       m_include_directories, m_filename);
578 
579   unsigned num_errors = m_parser->Parse(diagnostic_manager);
580 
581   // Check here for FixItHints.  If there are any try to apply the fixits and
582   // set the fixed text in m_fixed_text before returning an error.
583   if (num_errors) {
584     if (diagnostic_manager.HasFixIts()) {
585       if (m_parser->RewriteExpression(diagnostic_manager)) {
586         size_t fixed_start;
587         size_t fixed_end;
588         m_fixed_text = diagnostic_manager.GetFixedExpression();
589         // Retrieve the original expression in case we don't have a top level
590         // expression (which has no surrounding source code).
591         if (m_source_code && m_source_code->GetOriginalBodyBounds(
592                                  m_fixed_text, fixed_start, fixed_end))
593           m_fixed_text =
594               m_fixed_text.substr(fixed_start, fixed_end - fixed_start);
595       }
596     }
597     return false;
598   }
599 
600   //////////////////////////////////////////////////////////////////////////////
601   // Prepare the output of the parser for execution, evaluating it statically
602   // if possible
603   //
604 
605   {
606     Status jit_error = m_parser->PrepareForExecution(
607         m_jit_start_addr, m_jit_end_addr, m_execution_unit_sp, exe_ctx,
608         m_can_interpret, execution_policy);
609 
610     if (!jit_error.Success()) {
611       const char *error_cstr = jit_error.AsCString();
612       if (error_cstr && error_cstr[0])
613         diagnostic_manager.PutString(lldb::eSeverityError, error_cstr);
614       else
615         diagnostic_manager.PutString(lldb::eSeverityError,
616                                      "expression can't be interpreted or run");
617       return false;
618     }
619   }
620   return true;
621 }
622 
623 void ClangUserExpression::SetupCppModuleImports(ExecutionContext &exe_ctx) {
624   Log *log = GetLog(LLDBLog::Expressions);
625 
626   CppModuleConfiguration module_config =
627       GetModuleConfig(m_language.AsLanguageType(), exe_ctx);
628   m_imported_cpp_modules = module_config.GetImportedModules();
629   m_include_directories = module_config.GetIncludeDirs();
630 
631   LLDB_LOG(log, "List of imported modules in expression: {0}",
632            llvm::make_range(m_imported_cpp_modules.begin(),
633                             m_imported_cpp_modules.end()));
634   LLDB_LOG(log, "List of include directories gathered for modules: {0}",
635            llvm::make_range(m_include_directories.begin(),
636                             m_include_directories.end()));
637 }
638 
639 static bool shouldRetryWithCppModule(Target &target, ExecutionPolicy exe_policy) {
640   // Top-level expression don't yet support importing C++ modules.
641   if (exe_policy == ExecutionPolicy::eExecutionPolicyTopLevel)
642     return false;
643   return target.GetImportStdModule() == eImportStdModuleFallback;
644 }
645 
646 bool ClangUserExpression::Parse(DiagnosticManager &diagnostic_manager,
647                                 ExecutionContext &exe_ctx,
648                                 lldb_private::ExecutionPolicy execution_policy,
649                                 bool keep_result_in_memory,
650                                 bool generate_debug_info) {
651   Log *log = GetLog(LLDBLog::Expressions);
652 
653   if (!PrepareForParsing(diagnostic_manager, exe_ctx, /*for_completion*/ false))
654     return false;
655 
656   LLDB_LOGF(log, "Parsing the following code:\n%s", m_transformed_text.c_str());
657 
658   ////////////////////////////////////
659   // Set up the target and compiler
660   //
661 
662   Target *target = exe_ctx.GetTargetPtr();
663 
664   if (!target) {
665     diagnostic_manager.PutString(lldb::eSeverityError, "invalid target");
666     return false;
667   }
668 
669   //////////////////////////
670   // Parse the expression
671   //
672 
673   bool parse_success = TryParse(diagnostic_manager, exe_ctx, execution_policy,
674                                 keep_result_in_memory, generate_debug_info);
675   // If the expression failed to parse, check if retrying parsing with a loaded
676   // C++ module is possible.
677   if (!parse_success && shouldRetryWithCppModule(*target, execution_policy)) {
678     // Load the loaded C++ modules.
679     SetupCppModuleImports(exe_ctx);
680     // If we did load any modules, then retry parsing.
681     if (!m_imported_cpp_modules.empty()) {
682       // Create a dedicated diagnostic manager for the second parse attempt.
683       // These diagnostics are only returned to the caller if using the fallback
684       // actually succeeded in getting the expression to parse. This prevents
685       // that module-specific issues regress diagnostic quality with the
686       // fallback mode.
687       DiagnosticManager retry_manager;
688       // The module imports are injected into the source code wrapper,
689       // so recreate those.
690       CreateSourceCode(retry_manager, exe_ctx, m_imported_cpp_modules,
691                        /*for_completion*/ false);
692       parse_success = TryParse(retry_manager, exe_ctx, execution_policy,
693                                keep_result_in_memory, generate_debug_info);
694       // Return the parse diagnostics if we were successful.
695       if (parse_success)
696         diagnostic_manager = std::move(retry_manager);
697     }
698   }
699   if (!parse_success)
700     return false;
701 
702   if (m_execution_unit_sp) {
703     bool register_execution_unit = false;
704 
705     if (m_options.GetExecutionPolicy() == eExecutionPolicyTopLevel) {
706       register_execution_unit = true;
707     }
708 
709     // If there is more than one external function in the execution unit, it
710     // needs to keep living even if it's not top level, because the result
711     // could refer to that function.
712 
713     if (m_execution_unit_sp->GetJittedFunctions().size() > 1) {
714       register_execution_unit = true;
715     }
716 
717     if (register_execution_unit) {
718       if (auto *persistent_state =
719               exe_ctx.GetTargetPtr()->GetPersistentExpressionStateForLanguage(
720                   m_language.AsLanguageType()))
721         persistent_state->RegisterExecutionUnit(m_execution_unit_sp);
722     }
723   }
724 
725   if (generate_debug_info) {
726     lldb::ModuleSP jit_module_sp(m_execution_unit_sp->GetJITModule());
727 
728     if (jit_module_sp) {
729       ConstString const_func_name(FunctionName());
730       FileSpec jit_file;
731       jit_file.SetFilename(const_func_name);
732       jit_module_sp->SetFileSpecAndObjectName(jit_file, ConstString());
733       m_jit_module_wp = jit_module_sp;
734       target->GetImages().Append(jit_module_sp);
735     }
736   }
737 
738   Process *process = exe_ctx.GetProcessPtr();
739   if (process && m_jit_start_addr != LLDB_INVALID_ADDRESS)
740     m_jit_process_wp = lldb::ProcessWP(process->shared_from_this());
741   return true;
742 }
743 
744 /// Converts an absolute position inside a given code string into
745 /// a column/line pair.
746 ///
747 /// \param[in] abs_pos
748 ///     A absolute position in the code string that we want to convert
749 ///     to a column/line pair.
750 ///
751 /// \param[in] code
752 ///     A multi-line string usually representing source code.
753 ///
754 /// \param[out] line
755 ///     The line in the code that contains the given absolute position.
756 ///     The first line in the string is indexed as 1.
757 ///
758 /// \param[out] column
759 ///     The column in the line that contains the absolute position.
760 ///     The first character in a line is indexed as 0.
761 static void AbsPosToLineColumnPos(size_t abs_pos, llvm::StringRef code,
762                                   unsigned &line, unsigned &column) {
763   // Reset to code position to beginning of the file.
764   line = 0;
765   column = 0;
766 
767   assert(abs_pos <= code.size() && "Absolute position outside code string?");
768 
769   // We have to walk up to the position and count lines/columns.
770   for (std::size_t i = 0; i < abs_pos; ++i) {
771     // If we hit a line break, we go back to column 0 and enter a new line.
772     // We only handle \n because that's what we internally use to make new
773     // lines for our temporary code strings.
774     if (code[i] == '\n') {
775       ++line;
776       column = 0;
777       continue;
778     }
779     ++column;
780   }
781 }
782 
783 bool ClangUserExpression::Complete(ExecutionContext &exe_ctx,
784                                    CompletionRequest &request,
785                                    unsigned complete_pos) {
786   Log *log = GetLog(LLDBLog::Expressions);
787 
788   // We don't want any visible feedback when completing an expression. Mostly
789   // because the results we get from an incomplete invocation are probably not
790   // correct.
791   DiagnosticManager diagnostic_manager;
792 
793   if (!PrepareForParsing(diagnostic_manager, exe_ctx, /*for_completion*/ true))
794     return false;
795 
796   LLDB_LOGF(log, "Parsing the following code:\n%s", m_transformed_text.c_str());
797 
798   //////////////////////////
799   // Parse the expression
800   //
801 
802   m_materializer_up = std::make_unique<Materializer>();
803 
804   ResetDeclMap(exe_ctx, m_result_delegate, /*keep result in memory*/ true);
805 
806   auto on_exit = llvm::make_scope_exit([this]() { ResetDeclMap(); });
807 
808   if (!DeclMap()->WillParse(exe_ctx, GetMaterializer())) {
809     diagnostic_manager.PutString(
810         lldb::eSeverityError,
811         "current process state is unsuitable for expression parsing");
812 
813     return false;
814   }
815 
816   if (m_options.GetExecutionPolicy() == eExecutionPolicyTopLevel) {
817     DeclMap()->SetLookupsEnabled(true);
818   }
819 
820   ClangExpressionParser parser(exe_ctx.GetBestExecutionContextScope(), *this,
821                                false);
822 
823   // We have to find the source code location where the user text is inside
824   // the transformed expression code. When creating the transformed text, we
825   // already stored the absolute position in the m_transformed_text string. The
826   // only thing left to do is to transform it into the line:column format that
827   // Clang expects.
828 
829   // The line and column of the user expression inside the transformed source
830   // code.
831   unsigned user_expr_line, user_expr_column;
832   if (m_user_expression_start_pos)
833     AbsPosToLineColumnPos(*m_user_expression_start_pos, m_transformed_text,
834                           user_expr_line, user_expr_column);
835   else
836     return false;
837 
838   // The actual column where we have to complete is the start column of the
839   // user expression + the offset inside the user code that we were given.
840   const unsigned completion_column = user_expr_column + complete_pos;
841   parser.Complete(request, user_expr_line, completion_column, complete_pos);
842 
843   return true;
844 }
845 
846 lldb::addr_t ClangUserExpression::GetCppObjectPointer(
847     lldb::StackFrameSP frame_sp, llvm::StringRef object_name, Status &err) {
848   auto valobj_sp =
849       GetObjectPointerValueObject(std::move(frame_sp), object_name, err);
850 
851   // We're inside a C++ class method. This could potentially be an unnamed
852   // lambda structure. If the lambda captured a "this", that should be
853   // the object pointer.
854   if (auto thisChildSP = valobj_sp->GetChildMemberWithName("this")) {
855     valobj_sp = thisChildSP;
856   }
857 
858   if (!err.Success() || !valobj_sp.get())
859     return LLDB_INVALID_ADDRESS;
860 
861   lldb::addr_t ret = valobj_sp->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
862 
863   if (ret == LLDB_INVALID_ADDRESS) {
864     err = Status::FromErrorStringWithFormatv(
865         "Couldn't load '{0}' because its value couldn't be evaluated",
866         object_name);
867     return LLDB_INVALID_ADDRESS;
868   }
869 
870   return ret;
871 }
872 
873 bool ClangUserExpression::AddArguments(ExecutionContext &exe_ctx,
874                                        std::vector<lldb::addr_t> &args,
875                                        lldb::addr_t struct_address,
876                                        DiagnosticManager &diagnostic_manager) {
877   lldb::addr_t object_ptr = LLDB_INVALID_ADDRESS;
878   lldb::addr_t cmd_ptr = LLDB_INVALID_ADDRESS;
879 
880   if (m_needs_object_ptr) {
881     lldb::StackFrameSP frame_sp = exe_ctx.GetFrameSP();
882     if (!frame_sp)
883       return true;
884 
885     if (!m_in_cplusplus_method && !m_in_objectivec_method) {
886       diagnostic_manager.PutString(
887           lldb::eSeverityError,
888           "need object pointer but don't know the language");
889       return false;
890     }
891 
892     static constexpr llvm::StringLiteral g_cplusplus_object_name("this");
893     static constexpr llvm::StringLiteral g_objc_object_name("self");
894     llvm::StringRef object_name =
895         m_in_cplusplus_method ? g_cplusplus_object_name : g_objc_object_name;
896 
897     Status object_ptr_error;
898 
899     if (m_ctx_obj) {
900       AddressType address_type;
901       object_ptr = m_ctx_obj->GetAddressOf(false, &address_type);
902       if (object_ptr == LLDB_INVALID_ADDRESS ||
903           address_type != eAddressTypeLoad)
904         object_ptr_error = Status::FromErrorString("Can't get context object's "
905                                                    "debuggee address");
906     } else {
907       if (m_in_cplusplus_method) {
908         object_ptr =
909             GetCppObjectPointer(frame_sp, object_name, object_ptr_error);
910       } else {
911         object_ptr = GetObjectPointer(frame_sp, object_name, object_ptr_error);
912       }
913     }
914 
915     if (!object_ptr_error.Success()) {
916       exe_ctx.GetTargetRef().GetDebugger().GetAsyncOutputStream()->Format(
917           "warning: `{0}' is not accessible (substituting 0). {1}\n",
918           object_name, object_ptr_error.AsCString());
919       object_ptr = 0;
920     }
921 
922     if (m_in_objectivec_method) {
923       static constexpr llvm::StringLiteral cmd_name("_cmd");
924 
925       cmd_ptr = GetObjectPointer(frame_sp, cmd_name, object_ptr_error);
926 
927       if (!object_ptr_error.Success()) {
928         diagnostic_manager.Printf(
929             lldb::eSeverityWarning,
930             "couldn't get cmd pointer (substituting NULL): %s",
931             object_ptr_error.AsCString());
932         cmd_ptr = 0;
933       }
934     }
935 
936     args.push_back(object_ptr);
937 
938     if (m_in_objectivec_method)
939       args.push_back(cmd_ptr);
940 
941     args.push_back(struct_address);
942   } else {
943     args.push_back(struct_address);
944   }
945   return true;
946 }
947 
948 lldb::ExpressionVariableSP ClangUserExpression::GetResultAfterDematerialization(
949     ExecutionContextScope *exe_scope) {
950   return m_result_delegate.GetVariable();
951 }
952 
953 char ClangUserExpression::ClangUserExpressionHelper::ID;
954 
955 void ClangUserExpression::ClangUserExpressionHelper::ResetDeclMap(
956     ExecutionContext &exe_ctx,
957     Materializer::PersistentVariableDelegate &delegate,
958     bool keep_result_in_memory,
959     ValueObject *ctx_obj) {
960   std::shared_ptr<ClangASTImporter> ast_importer;
961   auto *state = exe_ctx.GetTargetSP()->GetPersistentExpressionStateForLanguage(
962       lldb::eLanguageTypeC);
963   if (state) {
964     auto *persistent_vars = llvm::cast<ClangPersistentVariables>(state);
965     ast_importer = persistent_vars->GetClangASTImporter();
966   }
967   m_expr_decl_map_up = std::make_unique<ClangExpressionDeclMap>(
968       keep_result_in_memory, &delegate, exe_ctx.GetTargetSP(), ast_importer,
969       ctx_obj);
970 }
971 
972 clang::ASTConsumer *
973 ClangUserExpression::ClangUserExpressionHelper::ASTTransformer(
974     clang::ASTConsumer *passthrough) {
975   m_result_synthesizer_up = std::make_unique<ASTResultSynthesizer>(
976       passthrough, m_top_level, m_target);
977 
978   return m_result_synthesizer_up.get();
979 }
980 
981 void ClangUserExpression::ClangUserExpressionHelper::CommitPersistentDecls() {
982   if (m_result_synthesizer_up) {
983     m_result_synthesizer_up->CommitPersistentDecls();
984   }
985 }
986 
987 ConstString ClangUserExpression::ResultDelegate::GetName() {
988   return m_persistent_state->GetNextPersistentVariableName(false);
989 }
990 
991 void ClangUserExpression::ResultDelegate::DidDematerialize(
992     lldb::ExpressionVariableSP &variable) {
993   m_variable = variable;
994 }
995 
996 void ClangUserExpression::ResultDelegate::RegisterPersistentState(
997     PersistentExpressionState *persistent_state) {
998   m_persistent_state = persistent_state;
999 }
1000 
1001 lldb::ExpressionVariableSP &ClangUserExpression::ResultDelegate::GetVariable() {
1002   return m_variable;
1003 }
1004