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 }
50 
51 static void PrintHeaderInfo(raw_ostream *OutputFile, StringRef Filename,
52                             bool ShowDepth, unsigned CurrentIncludeDepth,
53                             bool MSStyle) {
54   // Write to a temporary string to avoid unnecessary flushing on errs().
55   SmallString<512> Pathname(Filename);
56   if (!MSStyle)
57     Lexer::Stringify(Pathname);
58 
59   SmallString<256> Msg;
60   if (MSStyle)
61     Msg += "Note: including file:";
62 
63   if (ShowDepth) {
64     // The main source file is at depth 1, so skip one dot.
65     for (unsigned i = 1; i != CurrentIncludeDepth; ++i)
66       Msg += MSStyle ? ' ' : '.';
67 
68     if (!MSStyle)
69       Msg += ' ';
70   }
71   Msg += Pathname;
72   Msg += '\n';
73 
74   *OutputFile << Msg;
75   OutputFile->flush();
76 }
77 
78 void clang::AttachHeaderIncludeGen(Preprocessor &PP,
79                                    const DependencyOutputOptions &DepOpts,
80                                    bool ShowAllHeaders, StringRef OutputPath,
81                                    bool ShowDepth, bool MSStyle) {
82   raw_ostream *OutputFile = &llvm::errs();
83   bool OwnsOutputFile = false;
84 
85   // Choose output stream, when printing in cl.exe /showIncludes style.
86   if (MSStyle) {
87     switch (DepOpts.ShowIncludesDest) {
88     default:
89       llvm_unreachable("Invalid destination for /showIncludes output!");
90     case ShowIncludesDestination::Stderr:
91       OutputFile = &llvm::errs();
92       break;
93     case ShowIncludesDestination::Stdout:
94       OutputFile = &llvm::outs();
95       break;
96     }
97   }
98 
99   // Open the output file, if used.
100   if (!OutputPath.empty()) {
101     std::error_code EC;
102     llvm::raw_fd_ostream *OS = new llvm::raw_fd_ostream(
103         OutputPath.str(), EC,
104         llvm::sys::fs::OF_Append | llvm::sys::fs::OF_Text);
105     if (EC) {
106       PP.getDiagnostics().Report(clang::diag::warn_fe_cc_print_header_failure)
107           << EC.message();
108       delete OS;
109     } else {
110       OS->SetUnbuffered();
111       OutputFile = OS;
112       OwnsOutputFile = true;
113     }
114   }
115 
116   // Print header info for extra headers, pretending they were discovered by
117   // the regular preprocessor. The primary use case is to support proper
118   // generation of Make / Ninja file dependencies for implicit includes, such
119   // as sanitizer blacklists. It's only important for cl.exe compatibility,
120   // the GNU way to generate rules is -M / -MM / -MD / -MMD.
121   for (const auto &Header : DepOpts.ExtraDeps)
122     PrintHeaderInfo(OutputFile, Header, ShowDepth, 2, MSStyle);
123   PP.addPPCallbacks(std::make_unique<HeaderIncludesCallback>(
124       &PP, ShowAllHeaders, OutputFile, DepOpts, OwnsOutputFile, ShowDepth,
125       MSStyle));
126 }
127 
128 void HeaderIncludesCallback::FileChanged(SourceLocation Loc,
129                                          FileChangeReason Reason,
130                                        SrcMgr::CharacteristicKind NewFileType,
131                                        FileID PrevFID) {
132   // Unless we are exiting a #include, make sure to skip ahead to the line the
133   // #include directive was at.
134   PresumedLoc UserLoc = SM.getPresumedLoc(Loc);
135   if (UserLoc.isInvalid())
136     return;
137 
138   // Adjust the current include depth.
139   if (Reason == PPCallbacks::EnterFile) {
140     ++CurrentIncludeDepth;
141   } else if (Reason == PPCallbacks::ExitFile) {
142     if (CurrentIncludeDepth)
143       --CurrentIncludeDepth;
144 
145     // We track when we are done with the predefines by watching for the first
146     // place where we drop back to a nesting depth of 1.
147     if (CurrentIncludeDepth == 1 && !HasProcessedPredefines) {
148       if (!DepOpts.ShowIncludesPretendHeader.empty()) {
149         PrintHeaderInfo(OutputFile, DepOpts.ShowIncludesPretendHeader,
150                         ShowDepth, 2, MSStyle);
151       }
152       HasProcessedPredefines = true;
153     }
154 
155     return;
156   } else
157     return;
158 
159   // Show the header if we are (a) past the predefines, or (b) showing all
160   // headers and in the predefines at a depth past the initial file and command
161   // line buffers.
162   bool ShowHeader = (HasProcessedPredefines ||
163                      (ShowAllHeaders && CurrentIncludeDepth > 2));
164   unsigned IncludeDepth = CurrentIncludeDepth;
165   if (!HasProcessedPredefines)
166     --IncludeDepth; // Ignore indent from <built-in>.
167   else if (!DepOpts.ShowIncludesPretendHeader.empty())
168     ++IncludeDepth; // Pretend inclusion by ShowIncludesPretendHeader.
169 
170   // Dump the header include information we are past the predefines buffer or
171   // are showing all headers and this isn't the magic implicit <command line>
172   // header.
173   // FIXME: Identify headers in a more robust way than comparing their name to
174   // "<command line>" and "<built-in>" in a bunch of places.
175   if (ShowHeader && Reason == PPCallbacks::EnterFile &&
176       UserLoc.getFilename() != StringRef("<command line>")) {
177     PrintHeaderInfo(OutputFile, UserLoc.getFilename(), ShowDepth, IncludeDepth,
178                     MSStyle);
179   }
180 }
181