1 //===--- PrecompiledPreamble.h - Build precompiled preambles ----*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // Helper class to build precompiled preamble.
11 //===----------------------------------------------------------------------===//
13 #ifndef LLVM_CLANG_FRONTEND_PRECOMPILED_PREAMBLE_H
14 #define LLVM_CLANG_FRONTEND_PRECOMPILED_PREAMBLE_H
16 #include "clang/Lex/Lexer.h"
17 #include "clang/Lex/Preprocessor.h"
18 #include "llvm/ADT/IntrusiveRefCntPtr.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/Support/AlignOf.h"
21 #include "llvm/Support/MD5.h"
24 #include <system_error>
25 #include <type_traits>
29 class MemoryBufferRef;
36 class CompilerInstance;
37 class CompilerInvocation;
40 class PCHContainerOperations;
42 /// Runs lexer to compute suggested preamble bounds.
43 PreambleBounds ComputePreambleBounds(const LangOptions &LangOpts,
44 const llvm::MemoryBufferRef &Buffer,
47 class PreambleCallbacks;
49 /// A class holding a PCH and all information to check whether it is valid to
50 /// reuse the PCH for the subsequent runs. Use BuildPreamble to create PCH and
51 /// CanReusePreamble + AddImplicitPreamble to make use of it.
52 class PrecompiledPreamble {
54 struct PreambleFileHash;
57 /// Try to build PrecompiledPreamble for \p Invocation. See
58 /// BuildPreambleError for possible error codes.
60 /// \param Invocation Original CompilerInvocation with options to compile the
63 /// \param MainFileBuffer Buffer with the contents of the main file.
65 /// \param Bounds Bounds of the preamble, result of calling
66 /// ComputePreambleBounds.
68 /// \param Diagnostics Diagnostics engine to be used while building the
71 /// \param VFS An instance of vfs::FileSystem to be used for file
74 /// \param PCHContainerOps An instance of PCHContainerOperations.
76 /// \param StoreInMemory Store PCH in memory. If false, PCH will be stored in
79 /// \param Callbacks A set of callbacks to be executed when building
81 static llvm::ErrorOr<PrecompiledPreamble>
82 Build(const CompilerInvocation &Invocation,
83 const llvm::MemoryBuffer *MainFileBuffer, PreambleBounds Bounds,
84 DiagnosticsEngine &Diagnostics,
85 IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
86 std::shared_ptr<PCHContainerOperations> PCHContainerOps,
87 bool StoreInMemory, PreambleCallbacks &Callbacks);
89 PrecompiledPreamble(PrecompiledPreamble &&) = default;
90 PrecompiledPreamble &operator=(PrecompiledPreamble &&) = default;
92 /// PreambleBounds used to build the preamble.
93 PreambleBounds getBounds() const;
95 /// Returns the size, in bytes, that preamble takes on disk or in memory.
96 /// For on-disk preambles returns 0 if filesystem operations fail. Intended to
97 /// be used for logging and debugging purposes only.
98 std::size_t getSize() const;
100 /// Returned string is not null-terminated.
101 llvm::StringRef getContents() const {
102 return {PreambleBytes.data(), PreambleBytes.size()};
105 /// Check whether PrecompiledPreamble can be reused for the new contents(\p
106 /// MainFileBuffer) of the main file.
107 bool CanReuse(const CompilerInvocation &Invocation,
108 const llvm::MemoryBufferRef &MainFileBuffer,
109 PreambleBounds Bounds, llvm::vfs::FileSystem &VFS) const;
111 /// Changes options inside \p CI to use PCH from this preamble. Also remaps
112 /// main file to \p MainFileBuffer and updates \p VFS to ensure the preamble
114 /// Requires that CanReuse() is true.
115 /// For in-memory preambles, PrecompiledPreamble instance continues to own the
116 /// MemoryBuffer with the Preamble after this method returns. The caller is
117 /// responsible for making sure the PrecompiledPreamble instance outlives the
118 /// compiler run and the AST that will be using the PCH.
119 void AddImplicitPreamble(CompilerInvocation &CI,
120 IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
121 llvm::MemoryBuffer *MainFileBuffer) const;
123 /// Configure \p CI to use this preamble.
124 /// Like AddImplicitPreamble, but doesn't assume CanReuse() is true.
125 /// If this preamble does not match the file, it may parse differently.
126 void OverridePreamble(CompilerInvocation &CI,
127 IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
128 llvm::MemoryBuffer *MainFileBuffer) const;
131 PrecompiledPreamble(PCHStorage Storage, std::vector<char> PreambleBytes,
132 bool PreambleEndsAtStartOfLine,
133 llvm::StringMap<PreambleFileHash> FilesInPreamble,
134 llvm::StringSet<> MissingFiles);
136 /// A temp file that would be deleted on destructor call. If destructor is not
137 /// called for any reason, the file will be deleted at static objects'
139 /// An assertion will fire if two TempPCHFiles are created with the same name,
140 /// so it's not intended to be used outside preamble-handling.
143 // A main method used to construct TempPCHFile.
144 static llvm::ErrorOr<TempPCHFile> CreateNewPreamblePCHFile();
147 TempPCHFile(std::string FilePath);
150 TempPCHFile(TempPCHFile &&Other);
151 TempPCHFile &operator=(TempPCHFile &&Other);
153 TempPCHFile(const TempPCHFile &) = delete;
156 /// A path where temporary file is stored.
157 llvm::StringRef getFilePath() const;
160 void RemoveFileIfPresent();
163 llvm::Optional<std::string> FilePath;
166 class InMemoryPreamble {
173 enum class Kind { Empty, InMemory, TempFile };
175 PCHStorage() = default;
176 PCHStorage(TempPCHFile File);
177 PCHStorage(InMemoryPreamble Memory);
179 PCHStorage(const PCHStorage &) = delete;
180 PCHStorage &operator=(const PCHStorage &) = delete;
182 PCHStorage(PCHStorage &&Other);
183 PCHStorage &operator=(PCHStorage &&Other);
187 Kind getKind() const;
189 TempPCHFile &asFile();
190 const TempPCHFile &asFile() const;
192 InMemoryPreamble &asMemory();
193 const InMemoryPreamble &asMemory() const;
200 Kind StorageKind = Kind::Empty;
201 llvm::AlignedCharArrayUnion<TempPCHFile, InMemoryPreamble> Storage = {};
204 /// Data used to determine if a file used in the preamble has been changed.
205 struct PreambleFileHash {
206 /// All files have size set.
209 /// Modification time is set for files that are on disk. For memory
210 /// buffers it is zero.
213 /// Memory buffers have MD5 instead of modification time. We don't
214 /// compute MD5 for on-disk files because we hope that modification time is
215 /// enough to tell if the file was changed.
216 llvm::MD5::MD5Result MD5 = {};
218 static PreambleFileHash createForFile(off_t Size, time_t ModTime);
219 static PreambleFileHash
220 createForMemoryBuffer(const llvm::MemoryBufferRef &Buffer);
222 friend bool operator==(const PreambleFileHash &LHS,
223 const PreambleFileHash &RHS) {
224 return LHS.Size == RHS.Size && LHS.ModTime == RHS.ModTime &&
227 friend bool operator!=(const PreambleFileHash &LHS,
228 const PreambleFileHash &RHS) {
229 return !(LHS == RHS);
233 /// Helper function to set up PCH for the preamble into \p CI and \p VFS to
234 /// with the specified \p Bounds.
235 void configurePreamble(PreambleBounds Bounds, CompilerInvocation &CI,
236 IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
237 llvm::MemoryBuffer *MainFileBuffer) const;
239 /// Sets up the PreprocessorOptions and changes VFS, so that PCH stored in \p
240 /// Storage is accessible to clang. This method is an implementation detail of
241 /// AddImplicitPreamble.
243 setupPreambleStorage(const PCHStorage &Storage,
244 PreprocessorOptions &PreprocessorOpts,
245 IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS);
247 /// Manages the memory buffer or temporary file that stores the PCH.
249 /// Keeps track of the files that were used when computing the
250 /// preamble, with both their buffer size and their modification time.
252 /// If any of the files have changed from one compile to the next,
253 /// the preamble must be thrown away.
254 llvm::StringMap<PreambleFileHash> FilesInPreamble;
255 /// Files that were not found during preamble building. If any of these now
256 /// exist then the preamble should not be reused.
258 /// Storing *all* the missing files that could invalidate the preamble would
259 /// make it too expensive to revalidate (when the include path has many
260 /// entries, each #include will miss half of them on average).
261 /// Instead, we track only files that could have satisfied an #include that
262 /// was ultimately not found.
263 llvm::StringSet<> MissingFiles;
264 /// The contents of the file that was used to precompile the preamble. Only
265 /// contains first PreambleBounds::Size bytes. Used to compare if the relevant
266 /// part of the file has not changed, so that preamble can be reused.
267 std::vector<char> PreambleBytes;
268 /// See PreambleBounds::PreambleEndsAtStartOfLine
269 bool PreambleEndsAtStartOfLine;
272 /// A set of callbacks to gather useful information while building a preamble.
273 class PreambleCallbacks {
275 virtual ~PreambleCallbacks() = default;
277 /// Called before FrontendAction::BeginSourceFile.
278 /// Can be used to store references to various CompilerInstance fields
279 /// (e.g. SourceManager) that may be interesting to the consumers of other
281 virtual void BeforeExecute(CompilerInstance &CI);
282 /// Called after FrontendAction::Execute(), but before
283 /// FrontendAction::EndSourceFile(). Can be used to transfer ownership of
284 /// various CompilerInstance fields before they are destroyed.
285 virtual void AfterExecute(CompilerInstance &CI);
286 /// Called after PCH has been emitted. \p Writer may be used to retrieve
287 /// information about AST, serialized in PCH.
288 virtual void AfterPCHEmitted(ASTWriter &Writer);
289 /// Called for each TopLevelDecl.
290 /// NOTE: To allow more flexibility a custom ASTConsumer could probably be
291 /// used instead, but having only this method allows a simpler API.
292 virtual void HandleTopLevelDecl(DeclGroupRef DG);
293 /// Creates wrapper class for PPCallbacks so we can also process information
294 /// about includes that are inside of a preamble
295 virtual std::unique_ptr<PPCallbacks> createPPCallbacks();
296 /// The returned CommentHandler will be added to the preprocessor if not null.
297 virtual CommentHandler *getCommentHandler();
298 /// Determines which function bodies are parsed, by default skips everything.
299 /// Only used if FrontendOpts::SkipFunctionBodies is true.
300 /// See ASTConsumer::shouldSkipFunctionBody.
301 virtual bool shouldSkipFunctionBody(Decl *D) { return true; }
304 enum class BuildPreambleError {
305 CouldntCreateTempFile = 1,
306 CouldntCreateTargetInfo,
307 BeginSourceFileFailed,
312 class BuildPreambleErrorCategory final : public std::error_category {
314 const char *name() const noexcept override;
315 std::string message(int condition) const override;
318 std::error_code make_error_code(BuildPreambleError Error);
323 struct is_error_code_enum<clang::BuildPreambleError> : std::true_type {};