1 //===-- ClangModulesDeclVendor.cpp ------------------------------*- C++ -*-===//
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 <mutex>
10 
11 #include "clang/Basic/TargetInfo.h"
12 #include "clang/Frontend/CompilerInstance.h"
13 #include "clang/Frontend/FrontendActions.h"
14 #include "clang/Lex/Preprocessor.h"
15 #include "clang/Lex/PreprocessorOptions.h"
16 #include "clang/Parse/Parser.h"
17 #include "clang/Sema/Lookup.h"
18 #include "clang/Serialization/ASTReader.h"
19 #include "llvm/Support/FileSystem.h"
20 #include "llvm/Support/Path.h"
21 #include "llvm/Support/Threading.h"
22 
23 #include "ClangHost.h"
24 #include "ClangModulesDeclVendor.h"
25 #include "ModuleDependencyCollector.h"
26 
27 #include "lldb/Core/ModuleList.h"
28 #include "lldb/Host/Host.h"
29 #include "lldb/Host/HostInfo.h"
30 #include "lldb/Symbol/ClangASTContext.h"
31 #include "lldb/Symbol/CompileUnit.h"
32 #include "lldb/Symbol/SourceModule.h"
33 #include "lldb/Target/Target.h"
34 #include "lldb/Utility/FileSpec.h"
35 #include "lldb/Utility/LLDBAssert.h"
36 #include "lldb/Utility/Log.h"
37 #include "lldb/Utility/Reproducer.h"
38 #include "lldb/Utility/StreamString.h"
39 
40 using namespace lldb_private;
41 
42 namespace {
43 // Any Clang compiler requires a consumer for diagnostics.  This one stores
44 // them as strings so we can provide them to the user in case a module failed
45 // to load.
46 class StoringDiagnosticConsumer : public clang::DiagnosticConsumer {
47 public:
48   StoringDiagnosticConsumer();
49 
50   void HandleDiagnostic(clang::DiagnosticsEngine::Level DiagLevel,
51                         const clang::Diagnostic &info) override;
52 
53   void ClearDiagnostics();
54 
55   void DumpDiagnostics(Stream &error_stream);
56 
57 private:
58   typedef std::pair<clang::DiagnosticsEngine::Level, std::string>
59       IDAndDiagnostic;
60   std::vector<IDAndDiagnostic> m_diagnostics;
61   Log *m_log;
62 };
63 
64 // The private implementation of our ClangModulesDeclVendor.  Contains all the
65 // Clang state required to load modules.
66 class ClangModulesDeclVendorImpl : public ClangModulesDeclVendor {
67 public:
68   ClangModulesDeclVendorImpl(
69       llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diagnostics_engine,
70       std::shared_ptr<clang::CompilerInvocation> compiler_invocation,
71       std::unique_ptr<clang::CompilerInstance> compiler_instance,
72       std::unique_ptr<clang::Parser> parser);
73 
74   ~ClangModulesDeclVendorImpl() override = default;
75 
76   bool AddModule(const SourceModule &module, ModuleVector *exported_modules,
77                  Stream &error_stream) override;
78 
79   bool AddModulesForCompileUnit(CompileUnit &cu, ModuleVector &exported_modules,
80                                 Stream &error_stream) override;
81 
82   uint32_t FindDecls(ConstString name, bool append, uint32_t max_matches,
83                      std::vector<clang::NamedDecl *> &decls) override;
84 
85   void ForEachMacro(const ModuleVector &modules,
86                     std::function<bool(const std::string &)> handler) override;
87 
88   clang::ExternalASTMerger::ImporterSource GetImporterSource() override;
89 private:
90   void
91   ReportModuleExportsHelper(std::set<ClangModulesDeclVendor::ModuleID> &exports,
92                             clang::Module *module);
93 
94   void ReportModuleExports(ModuleVector &exports, clang::Module *module);
95 
96   clang::ModuleLoadResult DoGetModule(clang::ModuleIdPath path,
97                                       bool make_visible);
98 
99   bool m_enabled = false;
100 
101   llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> m_diagnostics_engine;
102   std::shared_ptr<clang::CompilerInvocation> m_compiler_invocation;
103   std::unique_ptr<clang::CompilerInstance> m_compiler_instance;
104   std::unique_ptr<clang::Parser> m_parser;
105   size_t m_source_location_index =
106       0; // used to give name components fake SourceLocations
107 
108   typedef std::vector<ConstString> ImportedModule;
109   typedef std::map<ImportedModule, clang::Module *> ImportedModuleMap;
110   typedef std::set<ModuleID> ImportedModuleSet;
111   ImportedModuleMap m_imported_modules;
112   ImportedModuleSet m_user_imported_modules;
113   const clang::ExternalASTMerger::OriginMap m_origin_map;
114   // We assume that every ASTContext has an ClangASTContext, so we also store
115   // a custom ClangASTContext for our internal ASTContext.
116   std::unique_ptr<ClangASTContext> m_ast_context;
117 };
118 } // anonymous namespace
119 
120 StoringDiagnosticConsumer::StoringDiagnosticConsumer() {
121   m_log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS);
122 }
123 
124 void StoringDiagnosticConsumer::HandleDiagnostic(
125     clang::DiagnosticsEngine::Level DiagLevel, const clang::Diagnostic &info) {
126   llvm::SmallVector<char, 256> diagnostic_string;
127 
128   info.FormatDiagnostic(diagnostic_string);
129 
130   m_diagnostics.push_back(
131       IDAndDiagnostic(DiagLevel, std::string(diagnostic_string.data(),
132                                              diagnostic_string.size())));
133 }
134 
135 void StoringDiagnosticConsumer::ClearDiagnostics() { m_diagnostics.clear(); }
136 
137 void StoringDiagnosticConsumer::DumpDiagnostics(Stream &error_stream) {
138   for (IDAndDiagnostic &diag : m_diagnostics) {
139     switch (diag.first) {
140     default:
141       error_stream.PutCString(diag.second);
142       error_stream.PutChar('\n');
143       break;
144     case clang::DiagnosticsEngine::Level::Ignored:
145       break;
146     }
147   }
148 }
149 
150 ClangModulesDeclVendor::ClangModulesDeclVendor() {}
151 
152 ClangModulesDeclVendor::~ClangModulesDeclVendor() {}
153 
154 ClangModulesDeclVendorImpl::ClangModulesDeclVendorImpl(
155     llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diagnostics_engine,
156     std::shared_ptr<clang::CompilerInvocation> compiler_invocation,
157     std::unique_ptr<clang::CompilerInstance> compiler_instance,
158     std::unique_ptr<clang::Parser> parser)
159     : m_diagnostics_engine(std::move(diagnostics_engine)),
160       m_compiler_invocation(std::move(compiler_invocation)),
161       m_compiler_instance(std::move(compiler_instance)),
162       m_parser(std::move(parser)), m_origin_map() {
163 
164   // Initialize our ClangASTContext.
165   auto target_opts = m_compiler_invocation->getTargetOpts();
166   m_ast_context.reset(new ClangASTContext(target_opts.Triple.c_str()));
167   m_ast_context->setASTContext(&m_compiler_instance->getASTContext());
168 }
169 
170 void ClangModulesDeclVendorImpl::ReportModuleExportsHelper(
171     std::set<ClangModulesDeclVendor::ModuleID> &exports,
172     clang::Module *module) {
173   if (exports.count(reinterpret_cast<ClangModulesDeclVendor::ModuleID>(module)))
174     return;
175 
176   exports.insert(reinterpret_cast<ClangModulesDeclVendor::ModuleID>(module));
177 
178   llvm::SmallVector<clang::Module *, 2> sub_exports;
179 
180   module->getExportedModules(sub_exports);
181 
182   for (clang::Module *module : sub_exports) {
183     ReportModuleExportsHelper(exports, module);
184   }
185 }
186 
187 void ClangModulesDeclVendorImpl::ReportModuleExports(
188     ClangModulesDeclVendor::ModuleVector &exports, clang::Module *module) {
189   std::set<ClangModulesDeclVendor::ModuleID> exports_set;
190 
191   ReportModuleExportsHelper(exports_set, module);
192 
193   for (ModuleID module : exports_set) {
194     exports.push_back(module);
195   }
196 }
197 
198 bool ClangModulesDeclVendorImpl::AddModule(const SourceModule &module,
199                                            ModuleVector *exported_modules,
200                                            Stream &error_stream) {
201   // Fail early.
202 
203   if (m_compiler_instance->hadModuleLoaderFatalFailure()) {
204     error_stream.PutCString("error: Couldn't load a module because the module "
205                             "loader is in a fatal state.\n");
206     return false;
207   }
208 
209   // Check if we've already imported this module.
210 
211   std::vector<ConstString> imported_module;
212 
213   for (ConstString path_component : module.path) {
214     imported_module.push_back(path_component);
215   }
216 
217   {
218     ImportedModuleMap::iterator mi = m_imported_modules.find(imported_module);
219 
220     if (mi != m_imported_modules.end()) {
221       if (exported_modules) {
222         ReportModuleExports(*exported_modules, mi->second);
223       }
224       return true;
225     }
226   }
227 
228   clang::HeaderSearch &HS =
229     m_compiler_instance->getPreprocessor().getHeaderSearchInfo();
230 
231   if (module.search_path) {
232     auto path_begin = llvm::sys::path::begin(module.search_path.GetStringRef());
233     auto path_end = llvm::sys::path::end(module.search_path.GetStringRef());
234     auto sysroot_begin = llvm::sys::path::begin(module.sysroot.GetStringRef());
235     auto sysroot_end = llvm::sys::path::end(module.sysroot.GetStringRef());
236     // FIXME: Use C++14 std::equal(it, it, it, it) variant once it's available.
237     bool is_system_module = (std::distance(path_begin, path_end) >=
238                              std::distance(sysroot_begin, sysroot_end)) &&
239                             std::equal(sysroot_begin, sysroot_end, path_begin);
240     // No need to inject search paths to modules in the sysroot.
241     if (!is_system_module) {
242       auto error = [&]() {
243         error_stream.Printf("error: No module map file in %s\n",
244                             module.search_path.AsCString());
245         return false;
246       };
247 
248       bool is_system = true;
249       bool is_framework = false;
250       auto dir =
251           HS.getFileMgr().getDirectory(module.search_path.GetStringRef());
252       if (!dir)
253         return error();
254       auto *file = HS.lookupModuleMapFile(*dir, is_framework);
255       if (!file)
256         return error();
257       if (!HS.loadModuleMapFile(file, is_system))
258         return error();
259     }
260   }
261   if (!HS.lookupModule(module.path.front().GetStringRef())) {
262     error_stream.Printf("error: Header search couldn't locate module %s\n",
263                         module.path.front().AsCString());
264     return false;
265   }
266 
267   llvm::SmallVector<std::pair<clang::IdentifierInfo *, clang::SourceLocation>,
268                     4>
269       clang_path;
270 
271   {
272     clang::SourceManager &source_manager =
273         m_compiler_instance->getASTContext().getSourceManager();
274 
275     for (ConstString path_component : module.path) {
276       clang_path.push_back(std::make_pair(
277           &m_compiler_instance->getASTContext().Idents.get(
278               path_component.GetStringRef()),
279           source_manager.getLocForStartOfFile(source_manager.getMainFileID())
280               .getLocWithOffset(m_source_location_index++)));
281     }
282   }
283 
284   StoringDiagnosticConsumer *diagnostic_consumer =
285       static_cast<StoringDiagnosticConsumer *>(
286           m_compiler_instance->getDiagnostics().getClient());
287 
288   diagnostic_consumer->ClearDiagnostics();
289 
290   clang::Module *top_level_module = DoGetModule(clang_path.front(), false);
291 
292   if (!top_level_module) {
293     diagnostic_consumer->DumpDiagnostics(error_stream);
294     error_stream.Printf("error: Couldn't load top-level module %s\n",
295                         module.path.front().AsCString());
296     return false;
297   }
298 
299   clang::Module *submodule = top_level_module;
300 
301   for (auto &component : llvm::ArrayRef<ConstString>(module.path).drop_front()) {
302     submodule = submodule->findSubmodule(component.GetStringRef());
303     if (!submodule) {
304       diagnostic_consumer->DumpDiagnostics(error_stream);
305       error_stream.Printf("error: Couldn't load submodule %s\n",
306                           component.GetCString());
307       return false;
308     }
309   }
310 
311   clang::Module *requested_module = DoGetModule(clang_path, true);
312 
313   if (requested_module != nullptr) {
314     if (exported_modules) {
315       ReportModuleExports(*exported_modules, requested_module);
316     }
317 
318     m_imported_modules[imported_module] = requested_module;
319 
320     m_enabled = true;
321 
322     return true;
323   }
324 
325   return false;
326 }
327 
328 bool ClangModulesDeclVendor::LanguageSupportsClangModules(
329     lldb::LanguageType language) {
330   switch (language) {
331   default:
332     return false;
333   case lldb::LanguageType::eLanguageTypeC:
334   case lldb::LanguageType::eLanguageTypeC11:
335   case lldb::LanguageType::eLanguageTypeC89:
336   case lldb::LanguageType::eLanguageTypeC99:
337   case lldb::LanguageType::eLanguageTypeC_plus_plus:
338   case lldb::LanguageType::eLanguageTypeC_plus_plus_03:
339   case lldb::LanguageType::eLanguageTypeC_plus_plus_11:
340   case lldb::LanguageType::eLanguageTypeC_plus_plus_14:
341   case lldb::LanguageType::eLanguageTypeObjC:
342   case lldb::LanguageType::eLanguageTypeObjC_plus_plus:
343     return true;
344   }
345 }
346 
347 bool ClangModulesDeclVendorImpl::AddModulesForCompileUnit(
348     CompileUnit &cu, ClangModulesDeclVendor::ModuleVector &exported_modules,
349     Stream &error_stream) {
350   if (LanguageSupportsClangModules(cu.GetLanguage())) {
351     for (auto &imported_module : cu.GetImportedModules())
352       if (!AddModule(imported_module, &exported_modules, error_stream))
353         return false;
354   }
355   return true;
356 }
357 
358 // ClangImporter::lookupValue
359 
360 uint32_t
361 ClangModulesDeclVendorImpl::FindDecls(ConstString name, bool append,
362                                       uint32_t max_matches,
363                                       std::vector<clang::NamedDecl *> &decls) {
364   if (!m_enabled) {
365     return 0;
366   }
367 
368   if (!append)
369     decls.clear();
370 
371   clang::IdentifierInfo &ident =
372       m_compiler_instance->getASTContext().Idents.get(name.GetStringRef());
373 
374   clang::LookupResult lookup_result(
375       m_compiler_instance->getSema(), clang::DeclarationName(&ident),
376       clang::SourceLocation(), clang::Sema::LookupOrdinaryName);
377 
378   m_compiler_instance->getSema().LookupName(
379       lookup_result,
380       m_compiler_instance->getSema().getScopeForContext(
381           m_compiler_instance->getASTContext().getTranslationUnitDecl()));
382 
383   uint32_t num_matches = 0;
384 
385   for (clang::NamedDecl *named_decl : lookup_result) {
386     if (num_matches >= max_matches)
387       return num_matches;
388 
389     decls.push_back(named_decl);
390     ++num_matches;
391   }
392 
393   return num_matches;
394 }
395 
396 void ClangModulesDeclVendorImpl::ForEachMacro(
397     const ClangModulesDeclVendor::ModuleVector &modules,
398     std::function<bool(const std::string &)> handler) {
399   if (!m_enabled) {
400     return;
401   }
402 
403   typedef std::map<ModuleID, ssize_t> ModulePriorityMap;
404   ModulePriorityMap module_priorities;
405 
406   ssize_t priority = 0;
407 
408   for (ModuleID module : modules) {
409     module_priorities[module] = priority++;
410   }
411 
412   if (m_compiler_instance->getPreprocessor().getExternalSource()) {
413     m_compiler_instance->getPreprocessor()
414         .getExternalSource()
415         ->ReadDefinedMacros();
416   }
417 
418   for (clang::Preprocessor::macro_iterator
419            mi = m_compiler_instance->getPreprocessor().macro_begin(),
420            me = m_compiler_instance->getPreprocessor().macro_end();
421        mi != me; ++mi) {
422     const clang::IdentifierInfo *ii = nullptr;
423 
424     {
425       if (clang::IdentifierInfoLookup *lookup =
426               m_compiler_instance->getPreprocessor()
427                   .getIdentifierTable()
428                   .getExternalIdentifierLookup()) {
429         lookup->get(mi->first->getName());
430       }
431       if (!ii) {
432         ii = mi->first;
433       }
434     }
435 
436     ssize_t found_priority = -1;
437     clang::MacroInfo *macro_info = nullptr;
438 
439     for (clang::ModuleMacro *module_macro :
440          m_compiler_instance->getPreprocessor().getLeafModuleMacros(ii)) {
441       clang::Module *module = module_macro->getOwningModule();
442 
443       {
444         ModulePriorityMap::iterator pi =
445             module_priorities.find(reinterpret_cast<ModuleID>(module));
446 
447         if (pi != module_priorities.end() && pi->second > found_priority) {
448           macro_info = module_macro->getMacroInfo();
449           found_priority = pi->second;
450         }
451       }
452 
453       clang::Module *top_level_module = module->getTopLevelModule();
454 
455       if (top_level_module != module) {
456         ModulePriorityMap::iterator pi = module_priorities.find(
457             reinterpret_cast<ModuleID>(top_level_module));
458 
459         if ((pi != module_priorities.end()) && pi->second > found_priority) {
460           macro_info = module_macro->getMacroInfo();
461           found_priority = pi->second;
462         }
463       }
464     }
465 
466     if (macro_info) {
467       std::string macro_expansion = "#define ";
468       macro_expansion.append(mi->first->getName().str());
469 
470       {
471         if (macro_info->isFunctionLike()) {
472           macro_expansion.append("(");
473 
474           bool first_arg = true;
475 
476           for (auto pi = macro_info->param_begin(),
477                     pe = macro_info->param_end();
478                pi != pe; ++pi) {
479             if (!first_arg) {
480               macro_expansion.append(", ");
481             } else {
482               first_arg = false;
483             }
484 
485             macro_expansion.append((*pi)->getName().str());
486           }
487 
488           if (macro_info->isC99Varargs()) {
489             if (first_arg) {
490               macro_expansion.append("...");
491             } else {
492               macro_expansion.append(", ...");
493             }
494           } else if (macro_info->isGNUVarargs()) {
495             macro_expansion.append("...");
496           }
497 
498           macro_expansion.append(")");
499         }
500 
501         macro_expansion.append(" ");
502 
503         bool first_token = true;
504 
505         for (clang::MacroInfo::tokens_iterator ti = macro_info->tokens_begin(),
506                                                te = macro_info->tokens_end();
507              ti != te; ++ti) {
508           if (!first_token) {
509             macro_expansion.append(" ");
510           } else {
511             first_token = false;
512           }
513 
514           if (ti->isLiteral()) {
515             if (const char *literal_data = ti->getLiteralData()) {
516               std::string token_str(literal_data, ti->getLength());
517               macro_expansion.append(token_str);
518             } else {
519               bool invalid = false;
520               const char *literal_source =
521                   m_compiler_instance->getSourceManager().getCharacterData(
522                       ti->getLocation(), &invalid);
523 
524               if (invalid) {
525                 lldbassert(0 && "Unhandled token kind");
526                 macro_expansion.append("<unknown literal value>");
527               } else {
528                 macro_expansion.append(
529                     std::string(literal_source, ti->getLength()));
530               }
531             }
532           } else if (const char *punctuator_spelling =
533                          clang::tok::getPunctuatorSpelling(ti->getKind())) {
534             macro_expansion.append(punctuator_spelling);
535           } else if (const char *keyword_spelling =
536                          clang::tok::getKeywordSpelling(ti->getKind())) {
537             macro_expansion.append(keyword_spelling);
538           } else {
539             switch (ti->getKind()) {
540             case clang::tok::TokenKind::identifier:
541               macro_expansion.append(ti->getIdentifierInfo()->getName().str());
542               break;
543             case clang::tok::TokenKind::raw_identifier:
544               macro_expansion.append(ti->getRawIdentifier().str());
545               break;
546             default:
547               macro_expansion.append(ti->getName());
548               break;
549             }
550           }
551         }
552 
553         if (handler(macro_expansion)) {
554           return;
555         }
556       }
557     }
558   }
559 }
560 
561 clang::ModuleLoadResult
562 ClangModulesDeclVendorImpl::DoGetModule(clang::ModuleIdPath path,
563                                         bool make_visible) {
564   clang::Module::NameVisibilityKind visibility =
565       make_visible ? clang::Module::AllVisible : clang::Module::Hidden;
566 
567   const bool is_inclusion_directive = false;
568 
569   return m_compiler_instance->loadModule(path.front().second, path, visibility,
570                                          is_inclusion_directive);
571 }
572 
573 clang::ExternalASTMerger::ImporterSource
574 ClangModulesDeclVendorImpl::GetImporterSource() {
575   return {m_compiler_instance->getASTContext(),
576           m_compiler_instance->getFileManager(), m_origin_map};
577 }
578 
579 static const char *ModuleImportBufferName = "LLDBModulesMemoryBuffer";
580 
581 lldb_private::ClangModulesDeclVendor *
582 ClangModulesDeclVendor::Create(Target &target) {
583   // FIXME we should insure programmatically that the expression parser's
584   // compiler and the modules runtime's
585   // compiler are both initialized in the same way – preferably by the same
586   // code.
587 
588   if (!target.GetPlatform()->SupportsModules())
589     return nullptr;
590 
591   const ArchSpec &arch = target.GetArchitecture();
592 
593   std::vector<std::string> compiler_invocation_arguments = {
594       "clang",
595       "-fmodules",
596       "-fimplicit-module-maps",
597       "-fcxx-modules",
598       "-fsyntax-only",
599       "-femit-all-decls",
600       "-target",
601       arch.GetTriple().str(),
602       "-fmodules-validate-system-headers",
603       "-Werror=non-modular-include-in-framework-module"};
604 
605   target.GetPlatform()->AddClangModuleCompilationOptions(
606       &target, compiler_invocation_arguments);
607 
608   compiler_invocation_arguments.push_back(ModuleImportBufferName);
609 
610   // Add additional search paths with { "-I", path } or { "-F", path } here.
611 
612   {
613     llvm::SmallString<128> path;
614     auto props = ModuleList::GetGlobalModuleListProperties();
615     props.GetClangModulesCachePath().GetPath(path);
616     std::string module_cache_argument("-fmodules-cache-path=");
617     module_cache_argument.append(path.str());
618     compiler_invocation_arguments.push_back(module_cache_argument);
619   }
620 
621   FileSpecList module_search_paths = target.GetClangModuleSearchPaths();
622 
623   for (size_t spi = 0, spe = module_search_paths.GetSize(); spi < spe; ++spi) {
624     const FileSpec &search_path = module_search_paths.GetFileSpecAtIndex(spi);
625 
626     std::string search_path_argument = "-I";
627     search_path_argument.append(search_path.GetPath());
628 
629     compiler_invocation_arguments.push_back(search_path_argument);
630   }
631 
632   {
633     FileSpec clang_resource_dir = GetClangResourceDir();
634 
635     if (FileSystem::Instance().IsDirectory(clang_resource_dir.GetPath())) {
636       compiler_invocation_arguments.push_back("-resource-dir");
637       compiler_invocation_arguments.push_back(clang_resource_dir.GetPath());
638     }
639   }
640 
641   llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diagnostics_engine =
642       clang::CompilerInstance::createDiagnostics(new clang::DiagnosticOptions,
643                                                  new StoringDiagnosticConsumer);
644 
645   std::vector<const char *> compiler_invocation_argument_cstrs;
646   compiler_invocation_argument_cstrs.reserve(
647       compiler_invocation_arguments.size());
648   for (const std::string &arg : compiler_invocation_arguments)
649     compiler_invocation_argument_cstrs.push_back(arg.c_str());
650 
651   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
652   LLDB_LOG(log, "ClangModulesDeclVendor's compiler flags {0:$[ ]}",
653            llvm::make_range(compiler_invocation_arguments.begin(),
654                             compiler_invocation_arguments.end()));
655 
656   std::shared_ptr<clang::CompilerInvocation> invocation =
657       clang::createInvocationFromCommandLine(compiler_invocation_argument_cstrs,
658                                              diagnostics_engine);
659 
660   if (!invocation)
661     return nullptr;
662 
663   std::unique_ptr<llvm::MemoryBuffer> source_buffer =
664       llvm::MemoryBuffer::getMemBuffer(
665           "extern int __lldb __attribute__((unavailable));",
666           ModuleImportBufferName);
667 
668   invocation->getPreprocessorOpts().addRemappedFile(ModuleImportBufferName,
669                                                     source_buffer.release());
670 
671   std::unique_ptr<clang::CompilerInstance> instance(
672       new clang::CompilerInstance);
673 
674   // When capturing a reproducer, hook up the file collector with clang to
675   // collector modules and headers.
676   if (repro::Generator *g = repro::Reproducer::Instance().GetGenerator()) {
677     repro::FileProvider &fp = g->GetOrCreate<repro::FileProvider>();
678     instance->setModuleDepCollector(
679         std::make_shared<ModuleDependencyCollectorAdaptor>(
680             fp.GetFileCollector()));
681     clang::DependencyOutputOptions &opts = instance->getDependencyOutputOpts();
682     opts.IncludeSystemHeaders = true;
683     opts.IncludeModuleFiles = true;
684   }
685 
686   // Make sure clang uses the same VFS as LLDB.
687   instance->createFileManager(FileSystem::Instance().GetVirtualFileSystem());
688   instance->setDiagnostics(diagnostics_engine.get());
689   instance->setInvocation(invocation);
690 
691   std::unique_ptr<clang::FrontendAction> action(new clang::SyntaxOnlyAction);
692 
693   instance->setTarget(clang::TargetInfo::CreateTargetInfo(
694       *diagnostics_engine, instance->getInvocation().TargetOpts));
695 
696   if (!instance->hasTarget())
697     return nullptr;
698 
699   instance->getTarget().adjust(instance->getLangOpts());
700 
701   if (!action->BeginSourceFile(*instance,
702                                instance->getFrontendOpts().Inputs[0]))
703     return nullptr;
704 
705   instance->getPreprocessor().enableIncrementalProcessing();
706 
707   instance->createModuleManager();
708 
709   instance->createSema(action->getTranslationUnitKind(), nullptr);
710 
711   const bool skipFunctionBodies = false;
712   std::unique_ptr<clang::Parser> parser(new clang::Parser(
713       instance->getPreprocessor(), instance->getSema(), skipFunctionBodies));
714 
715   instance->getPreprocessor().EnterMainSourceFile();
716   parser->Initialize();
717 
718   clang::Parser::DeclGroupPtrTy parsed;
719 
720   while (!parser->ParseTopLevelDecl(parsed))
721     ;
722 
723   return new ClangModulesDeclVendorImpl(std::move(diagnostics_engine),
724                                         std::move(invocation),
725                                         std::move(instance), std::move(parser));
726 }
727