1 //===-- HeaderIncludeGen.cpp - Generate Header Includes -------------------===//
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 "clang/Frontend/DependencyOutputOptions.h"
10 #include "clang/Frontend/Utils.h"
11 #include "clang/Basic/SourceManager.h"
12 #include "clang/Frontend/FrontendDiagnostic.h"
13 #include "clang/Lex/Preprocessor.h"
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/Support/raw_ostream.h"
16 using namespace clang;
17 
18 namespace {
19 class HeaderIncludesCallback : public PPCallbacks {
20   SourceManager &SM;
21   raw_ostream *OutputFile;
22   const DependencyOutputOptions &DepOpts;
23   unsigned CurrentIncludeDepth;
24   bool HasProcessedPredefines;
25   bool OwnsOutputFile;
26   bool ShowAllHeaders;
27   bool ShowDepth;
28   bool MSStyle;
29 
30 public:
31   HeaderIncludesCallback(const Preprocessor *PP, bool ShowAllHeaders_,
32                          raw_ostream *OutputFile_,
33                          const DependencyOutputOptions &DepOpts,
34                          bool OwnsOutputFile_, bool ShowDepth_, bool MSStyle_)
35       : SM(PP->getSourceManager()), OutputFile(OutputFile_), DepOpts(DepOpts),
36         CurrentIncludeDepth(0), HasProcessedPredefines(false),
37         OwnsOutputFile(OwnsOutputFile_), ShowAllHeaders(ShowAllHeaders_),
38         ShowDepth(ShowDepth_), MSStyle(MSStyle_) {}
39 
40   ~HeaderIncludesCallback() override {
41     if (OwnsOutputFile)
42       delete OutputFile;
43   }
44 
45   void FileChanged(SourceLocation Loc, FileChangeReason Reason,
46                    SrcMgr::CharacteristicKind FileType,
47                    FileID PrevFID) override;
48 
49   void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,
50                    SrcMgr::CharacteristicKind FileType) override;
51 };
52 }
53 
54 static void PrintHeaderInfo(raw_ostream *OutputFile, StringRef Filename,
55                             bool ShowDepth, unsigned CurrentIncludeDepth,
56                             bool MSStyle) {
57   // Write to a temporary string to avoid unnecessary flushing on errs().
58   SmallString<512> Pathname(Filename);
59   if (!MSStyle)
60     Lexer::Stringify(Pathname);
61 
62   SmallString<256> Msg;
63   if (MSStyle)
64     Msg += "Note: including file:";
65 
66   if (ShowDepth) {
67     // The main source file is at depth 1, so skip one dot.
68     for (unsigned i = 1; i != CurrentIncludeDepth; ++i)
69       Msg += MSStyle ? ' ' : '.';
70 
71     if (!MSStyle)
72       Msg += ' ';
73   }
74   Msg += Pathname;
75   Msg += '\n';
76 
77   *OutputFile << Msg;
78   OutputFile->flush();
79 }
80 
81 void clang::AttachHeaderIncludeGen(Preprocessor &PP,
82                                    const DependencyOutputOptions &DepOpts,
83                                    bool ShowAllHeaders, StringRef OutputPath,
84                                    bool ShowDepth, bool MSStyle) {
85   raw_ostream *OutputFile = &llvm::errs();
86   bool OwnsOutputFile = false;
87 
88   // Choose output stream, when printing in cl.exe /showIncludes style.
89   if (MSStyle) {
90     switch (DepOpts.ShowIncludesDest) {
91     default:
92       llvm_unreachable("Invalid destination for /showIncludes output!");
93     case ShowIncludesDestination::Stderr:
94       OutputFile = &llvm::errs();
95       break;
96     case ShowIncludesDestination::Stdout:
97       OutputFile = &llvm::outs();
98       break;
99     }
100   }
101 
102   // Open the output file, if used.
103   if (!OutputPath.empty()) {
104     std::error_code EC;
105     llvm::raw_fd_ostream *OS = new llvm::raw_fd_ostream(
106         OutputPath.str(), EC,
107         llvm::sys::fs::OF_Append | llvm::sys::fs::OF_TextWithCRLF);
108     if (EC) {
109       PP.getDiagnostics().Report(clang::diag::warn_fe_cc_print_header_failure)
110           << EC.message();
111       delete OS;
112     } else {
113       OS->SetUnbuffered();
114       OutputFile = OS;
115       OwnsOutputFile = true;
116     }
117   }
118 
119   // Print header info for extra headers, pretending they were discovered by
120   // the regular preprocessor. The primary use case is to support proper
121   // generation of Make / Ninja file dependencies for implicit includes, such
122   // as sanitizer ignorelists. It's only important for cl.exe compatibility,
123   // the GNU way to generate rules is -M / -MM / -MD / -MMD.
124   for (const auto &Header : DepOpts.ExtraDeps)
125     PrintHeaderInfo(OutputFile, Header.first, ShowDepth, 2, MSStyle);
126   PP.addPPCallbacks(std::make_unique<HeaderIncludesCallback>(
127       &PP, ShowAllHeaders, OutputFile, DepOpts, OwnsOutputFile, ShowDepth,
128       MSStyle));
129 }
130 
131 void HeaderIncludesCallback::FileChanged(SourceLocation Loc,
132                                          FileChangeReason Reason,
133                                          SrcMgr::CharacteristicKind NewFileType,
134                                          FileID PrevFID) {
135   // Unless we are exiting a #include, make sure to skip ahead to the line the
136   // #include directive was at.
137   PresumedLoc UserLoc = SM.getPresumedLoc(Loc);
138   if (UserLoc.isInvalid())
139     return;
140 
141   // Adjust the current include depth.
142   if (Reason == PPCallbacks::EnterFile) {
143     ++CurrentIncludeDepth;
144   } else if (Reason == PPCallbacks::ExitFile) {
145     if (CurrentIncludeDepth)
146       --CurrentIncludeDepth;
147 
148     // We track when we are done with the predefines by watching for the first
149     // place where we drop back to a nesting depth of 1.
150     if (CurrentIncludeDepth == 1 && !HasProcessedPredefines) {
151       if (!DepOpts.ShowIncludesPretendHeader.empty()) {
152         PrintHeaderInfo(OutputFile, DepOpts.ShowIncludesPretendHeader,
153                         ShowDepth, 2, MSStyle);
154       }
155       HasProcessedPredefines = true;
156     }
157 
158     return;
159   } else
160     return;
161 
162   // Show the header if we are (a) past the predefines, or (b) showing all
163   // headers and in the predefines at a depth past the initial file and command
164   // line buffers.
165   bool ShowHeader = (HasProcessedPredefines ||
166                      (ShowAllHeaders && CurrentIncludeDepth > 2));
167   unsigned IncludeDepth = CurrentIncludeDepth;
168   if (!HasProcessedPredefines)
169     --IncludeDepth; // Ignore indent from <built-in>.
170   else if (!DepOpts.ShowIncludesPretendHeader.empty())
171     ++IncludeDepth; // Pretend inclusion by ShowIncludesPretendHeader.
172 
173   if (!DepOpts.IncludeSystemHeaders && isSystem(NewFileType))
174     ShowHeader = false;
175 
176   // Dump the header include information we are past the predefines buffer or
177   // are showing all headers and this isn't the magic implicit <command line>
178   // header.
179   // FIXME: Identify headers in a more robust way than comparing their name to
180   // "<command line>" and "<built-in>" in a bunch of places.
181   if (ShowHeader && Reason == PPCallbacks::EnterFile &&
182       UserLoc.getFilename() != StringRef("<command line>")) {
183     PrintHeaderInfo(OutputFile, UserLoc.getFilename(), ShowDepth, IncludeDepth,
184                     MSStyle);
185   }
186 }
187 
188 void HeaderIncludesCallback::FileSkipped(const FileEntryRef &SkippedFile, const
189                                          Token &FilenameTok,
190                                          SrcMgr::CharacteristicKind FileType) {
191   if (!DepOpts.ShowSkippedHeaderIncludes)
192     return;
193 
194   if (!DepOpts.IncludeSystemHeaders && isSystem(FileType))
195     return;
196 
197   PrintHeaderInfo(OutputFile, SkippedFile.getName(), ShowDepth,
198                   CurrentIncludeDepth + 1, MSStyle);
199 }
200