clang-tools 17.0.0git
CanonicalIncludes.h
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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
31namespace clang {
32namespace 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.
38public:
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 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
58private:
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 common):
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
90std::unique_ptr<CommentHandler>
92
93} // namespace clangd
94} // namespace clang
95
96#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_CANONICALINCLUDES_H
Maps a definition location onto an #include file, based on a set of filename rules.
void addMapping(FileEntryRef Header, llvm::StringRef CanonicalPath)
Adds a file-to-string mapping from ID to CanonicalPath.
void addSystemHeadersMapping(const LangOptions &Language)
Adds mapping for system headers and some special symbols (e.g.
llvm::StringRef mapHeader(FileEntryRef Header) const
Returns the overridden include for files in Header, or "".
llvm::StringRef mapSymbol(llvm::StringRef QualifiedName) const
Returns the overridden include for symbol with QualifiedName, or "".
std::unique_ptr< CommentHandler > collectIWYUHeaderMaps(CanonicalIncludes *Includes)
Returns a CommentHandler that parses pragma comment on include files to determine when we should incl...
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//