1 //===-- CanonicalIncludes.h - remap #include header -------------*- 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 // At indexing time, we decide which file to #included for a symbol. 10 // Usually this is the file with the canonical decl, but there are exceptions: 11 // - private headers may have pragmas pointing to the matching public header. 12 // (These are "IWYU" pragmas, named after the include-what-you-use tool). 13 // - the standard library is implemented in many files, without any pragmas. 14 // We have a lookup table for common standard library implementations. 15 // libstdc++ puts char_traits in bits/char_traits.h, but we #include <string>. 16 // 17 //===----------------------------------------------------------------------===// 18 19 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_CANONICALINCLUDES_H 20 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_CANONICALINCLUDES_H 21 22 #include "clang/Basic/FileEntry.h" 23 #include "clang/Lex/Preprocessor.h" 24 #include "llvm/ADT/StringMap.h" 25 #include "llvm/ADT/StringRef.h" 26 #include "llvm/Support/FileSystem/UniqueID.h" 27 #include <mutex> 28 #include <string> 29 #include <vector> 30 31 namespace clang { 32 namespace clangd { 33 34 /// Maps a definition location onto an #include file, based on a set of filename 35 /// rules. 36 /// Only const methods (i.e. mapHeader) in this class are thread safe. 37 class CanonicalIncludes { 38 public: 39 /// Adds a file-to-string mapping from \p ID to \p CanonicalPath. 40 void addMapping(FileEntryRef Header, llvm::StringRef CanonicalPath); 41 42 /// Returns the overridden include for symbol with \p QualifiedName, or "". 43 llvm::StringRef mapSymbol(llvm::StringRef QualifiedName) const; 44 45 /// Returns the overridden include for for files in \p Header, or "". 46 llvm::StringRef mapHeader(FileEntryRef Header) const; 47 48 /// Adds mapping for system headers and some special symbols (e.g. STL symbols 49 /// in <iosfwd> need to be mapped individually). Approximately, the following 50 /// system headers are handled: 51 /// - C++ standard library e.g. bits/basic_string.h$ -> <string> 52 /// - Posix library e.g. bits/pthreadtypes.h$ -> <pthread.h> 53 /// - Compiler extensions, e.g. include/avx512bwintrin.h$ -> <immintrin.h> 54 /// The mapping is hardcoded and hand-maintained, so it might not cover all 55 /// headers. 56 void addSystemHeadersMapping(const LangOptions &Language); 57 58 private: 59 /// A map from the private header to a canonical include path. 60 llvm::DenseMap<llvm::sys::fs::UniqueID, std::string> FullPathMapping; 61 /// A map from a suffix (one or components of a path) to a canonical path. 62 /// Used only for mapping standard headers. 63 const llvm::StringMap<llvm::StringRef> *StdSuffixHeaderMapping = nullptr; 64 /// A map from fully qualified symbol names to header names. 65 /// Used only for mapping standard symbols. 66 const llvm::StringMap<llvm::StringRef> *StdSymbolMapping = nullptr; 67 }; 68 69 /// Returns a CommentHandler that parses pragma comment on include files to 70 /// determine when we should include a different header from the header that 71 /// directly defines a symbol. Mappinps are registered with \p Includes. 72 /// 73 /// Currently it only supports IWYU private pragma: 74 /// https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/IWYUPragmas.md#iwyu-pragma-private 75 /// 76 /// We ignore other pragmas: 77 /// - keep: this is common but irrelevant: we do not currently remove includes 78 /// - export: this is common and potentially interesting, there are three cases: 79 /// * Points to a public header (common): we can suppress include2 if you 80 /// already have include1. Only marginally useful. 81 /// * Points to a private header annotated with `private` (somewhat commmon): 82 /// Not incrementally useful as we support private. 83 /// * Points to a private header without pragmas (rare). This is a reversed 84 /// private pragma, and is valuable but too rare to be worthwhile. 85 /// - no_include: this is about as common as private, but only affects the 86 /// current file, so the value is smaller. We could add support. 87 /// - friend: this is less common than private, has implementation difficulties, 88 /// and affects behavior in a limited scope. 89 /// - associated: extremely rare 90 std::unique_ptr<CommentHandler> 91 collectIWYUHeaderMaps(CanonicalIncludes *Includes); 92 93 } // namespace clangd 94 } // namespace clang 95 96 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_CANONICALINCLUDES_H 97