1//===--- DependencyFile.cpp - Generate dependency file --------------------===//
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// This code generates dependency files.
10//
11//===----------------------------------------------------------------------===//
12
13#include "clang/Frontend/Utils.h"
14#include "clang/Basic/FileManager.h"
15#include "clang/Basic/SourceManager.h"
16#include "clang/Frontend/DependencyOutputOptions.h"
17#include "clang/Frontend/FrontendDiagnostic.h"
18#include "clang/Lex/DirectoryLookup.h"
19#include "clang/Lex/ModuleMap.h"
20#include "clang/Lex/PPCallbacks.h"
21#include "clang/Lex/Preprocessor.h"
22#include "clang/Serialization/ASTReader.h"
23#include "llvm/ADT/StringSet.h"
24#include "llvm/ADT/StringSwitch.h"
25#include "llvm/Support/FileSystem.h"
26#include "llvm/Support/Path.h"
27#include "llvm/Support/raw_ostream.h"
28
29using namespace clang;
30
31namespace {
32struct DepCollectorPPCallbacks : public PPCallbacks {
33  DependencyCollector &DepCollector;
34  SourceManager &SM;
35  DiagnosticsEngine &Diags;
36  DepCollectorPPCallbacks(DependencyCollector &L, SourceManager &SM,
37                          DiagnosticsEngine &Diags)
38      : DepCollector(L), SM(SM), Diags(Diags) {}
39
40  void FileChanged(SourceLocation Loc, FileChangeReason Reason,
41                   SrcMgr::CharacteristicKind FileType,
42                   FileID PrevFID) override {
43    if (Reason != PPCallbacks::EnterFile)
44      return;
45
46    // Dependency generation really does want to go all the way to the
47    // file entry for a source location to find out what is depended on.
48    // We do not want #line markers to affect dependency generation!
49    Optional<FileEntryRef> File =
50        SM.getFileEntryRefForID(SM.getFileID(SM.getExpansionLoc(Loc)));
51    if (!File)
52      return;
53
54    StringRef Filename =
55        llvm::sys::path::remove_leading_dotslash(File->getName());
56
57    DepCollector.maybeAddDependency(Filename, /*FromModule*/false,
58                                    isSystem(FileType),
59                                    /*IsModuleFile*/false, /*IsMissing*/false);
60  }
61
62  void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,
63                   SrcMgr::CharacteristicKind FileType) override {
64    StringRef Filename =
65        llvm::sys::path::remove_leading_dotslash(SkippedFile.getName());
66    DepCollector.maybeAddDependency(Filename, /*FromModule=*/false,
67                                    /*IsSystem=*/isSystem(FileType),
68                                    /*IsModuleFile=*/false,
69                                    /*IsMissing=*/false);
70  }
71
72  void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,
73                          StringRef FileName, bool IsAngled,
74                          CharSourceRange FilenameRange, const FileEntry *File,
75                          StringRef SearchPath, StringRef RelativePath,
76                          const Module *Imported,
77                          SrcMgr::CharacteristicKind FileType) override {
78    if (!File)
79      DepCollector.maybeAddDependency(FileName, /*FromModule*/false,
80                                     /*IsSystem*/false, /*IsModuleFile*/false,
81                                     /*IsMissing*/true);
82    // Files that actually exist are handled by FileChanged.
83  }
84
85  void HasInclude(SourceLocation Loc, StringRef SpelledFilename, bool IsAngled,
86                  Optional<FileEntryRef> File,
87                  SrcMgr::CharacteristicKind FileType) override {
88    if (!File)
89      return;
90    StringRef Filename =
91        llvm::sys::path::remove_leading_dotslash(File->getName());
92    DepCollector.maybeAddDependency(Filename, /*FromModule=*/false,
93                                    /*IsSystem=*/isSystem(FileType),
94                                    /*IsModuleFile=*/false,
95                                    /*IsMissing=*/false);
96  }
97
98  void EndOfMainFile() override { DepCollector.finishedMainFile(Diags); }
99};
100
101struct DepCollectorMMCallbacks : public ModuleMapCallbacks {
102  DependencyCollector &DepCollector;
103  DepCollectorMMCallbacks(DependencyCollector &DC) : DepCollector(DC) {}
104
105  void moduleMapFileRead(SourceLocation Loc, const FileEntry &Entry,
106                         bool IsSystem) override {
107    StringRef Filename = Entry.getName();
108    DepCollector.maybeAddDependency(Filename, /*FromModule*/false,
109                                    /*IsSystem*/IsSystem,
110                                    /*IsModuleFile*/false,
111                                    /*IsMissing*/false);
112  }
113};
114
115struct DepCollectorASTListener : public ASTReaderListener {
116  DependencyCollector &DepCollector;
117  DepCollectorASTListener(DependencyCollector &L) : DepCollector(L) { }
118  bool needsInputFileVisitation() override { return true; }
119  bool needsSystemInputFileVisitation() override {
120    return DepCollector.needSystemDependencies();
121  }
122  void visitModuleFile(StringRef Filename,
123                       serialization::ModuleKind Kind) override {
124    DepCollector.maybeAddDependency(Filename, /*FromModule*/true,
125                                   /*IsSystem*/false, /*IsModuleFile*/true,
126                                   /*IsMissing*/false);
127  }
128  bool visitInputFile(StringRef Filename, bool IsSystem,
129                      bool IsOverridden, bool IsExplicitModule) override {
130    if (IsOverridden || IsExplicitModule)
131      return true;
132
133    DepCollector.maybeAddDependency(Filename, /*FromModule*/true, IsSystem,
134                                   /*IsModuleFile*/false, /*IsMissing*/false);
135    return true;
136  }
137};
138} // end anonymous namespace
139
140void DependencyCollector::maybeAddDependency(StringRef Filename, bool FromModule,
141                                            bool IsSystem, bool IsModuleFile,
142                                            bool IsMissing) {
143  if (sawDependency(Filename, FromModule, IsSystem, IsModuleFile, IsMissing))
144    addDependency(Filename);
145}
146
147bool DependencyCollector::addDependency(StringRef Filename) {
148  if (Seen.insert(Filename).second) {
149    Dependencies.push_back(Filename);
150    return true;
151  }
152  return false;
153}
154
155static bool isSpecialFilename(StringRef Filename) {
156  return llvm::StringSwitch<bool>(Filename)
157      .Case("<built-in>", true)
158      .Case("<stdin>", true)
159      .Default(false);
160}
161
162bool DependencyCollector::sawDependency(StringRef Filename, bool FromModule,
163                                       bool IsSystem, bool IsModuleFile,
164                                       bool IsMissing) {
165  return !isSpecialFilename(Filename) &&
166         (needSystemDependencies() || !IsSystem);
167}
168
169DependencyCollector::~DependencyCollector() { }
170void DependencyCollector::attachToPreprocessor(Preprocessor &PP) {
171  PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(
172      *this, PP.getSourceManager(), PP.getDiagnostics()));
173  PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
174      std::make_unique<DepCollectorMMCallbacks>(*this));
175}
176void DependencyCollector::attachToASTReader(ASTReader &R) {
177  R.addListener(std::make_unique<DepCollectorASTListener>(*this));
178}
179
180DependencyFileGenerator::DependencyFileGenerator(
181    const DependencyOutputOptions &Opts)
182    : OutputFile(Opts.OutputFile), Targets(Opts.Targets),
183      IncludeSystemHeaders(Opts.IncludeSystemHeaders),
184      PhonyTarget(Opts.UsePhonyTargets),
185      AddMissingHeaderDeps(Opts.AddMissingHeaderDeps), SeenMissingHeader(false),
186      IncludeModuleFiles(Opts.IncludeModuleFiles),
187      OutputFormat(Opts.OutputFormat), InputFileIndex(0) {
188  for (const auto &ExtraDep : Opts.ExtraDeps) {
189    if (addDependency(ExtraDep))
190      ++InputFileIndex;
191  }
192}
193
194void DependencyFileGenerator::attachToPreprocessor(Preprocessor &PP) {
195  // Disable the "file not found" diagnostic if the -MG option was given.
196  if (AddMissingHeaderDeps)
197    PP.SetSuppressIncludeNotFoundError(true);
198
199  DependencyCollector::attachToPreprocessor(PP);
200}
201
202bool DependencyFileGenerator::sawDependency(StringRef Filename, bool FromModule,
203                                            bool IsSystem, bool IsModuleFile,
204                                            bool IsMissing) {
205  if (IsMissing) {
206    // Handle the case of missing file from an inclusion directive.
207    if (AddMissingHeaderDeps)
208      return true;
209    SeenMissingHeader = true;
210    return false;
211  }
212  if (IsModuleFile && !IncludeModuleFiles)
213    return false;
214
215  if (isSpecialFilename(Filename))
216    return false;
217
218  if (IncludeSystemHeaders)
219    return true;
220
221  return !IsSystem;
222}
223
224void DependencyFileGenerator::finishedMainFile(DiagnosticsEngine &Diags) {
225  outputDependencyFile(Diags);
226}
227
228/// Print the filename, with escaping or quoting that accommodates the three
229/// most likely tools that use dependency files: GNU Make, BSD Make, and
230/// NMake/Jom.
231///
232/// BSD Make is the simplest case: It does no escaping at all.  This means
233/// characters that are normally delimiters, i.e. space and # (the comment
234/// character) simply aren't supported in filenames.
235///
236/// GNU Make does allow space and # in filenames, but to avoid being treated
237/// as a delimiter or comment, these must be escaped with a backslash. Because
238/// backslash is itself the escape character, if a backslash appears in a
239/// filename, it should be escaped as well.  (As a special case, $ is escaped
240/// as $$, which is the normal Make way to handle the $ character.)
241/// For compatibility with BSD Make and historical practice, if GNU Make
242/// un-escapes characters in a filename but doesn't find a match, it will
243/// retry with the unmodified original string.
244///
245/// GCC tries to accommodate both Make formats by escaping any space or #
246/// characters in the original filename, but not escaping backslashes.  The
247/// apparent intent is so that filenames with backslashes will be handled
248/// correctly by BSD Make, and by GNU Make in its fallback mode of using the
249/// unmodified original string; filenames with # or space characters aren't
250/// supported by BSD Make at all, but will be handled correctly by GNU Make
251/// due to the escaping.
252///
253/// A corner case that GCC gets only partly right is when the original filename
254/// has a backslash immediately followed by space or #.  GNU Make would expect
255/// this backslash to be escaped; however GCC escapes the original backslash
256/// only when followed by space, not #.  It will therefore take a dependency
257/// from a directive such as
258///     #include "a\ b\#c.h"
259/// and emit it as
260///     a\\\ b\\#c.h
261/// which GNU Make will interpret as
262///     a\ b\
263/// followed by a comment. Failing to find this file, it will fall back to the
264/// original string, which probably doesn't exist either; in any case it won't
265/// find
266///     a\ b\#c.h
267/// which is the actual filename specified by the include directive.
268///
269/// Clang does what GCC does, rather than what GNU Make expects.
270///
271/// NMake/Jom has a different set of scary characters, but wraps filespecs in
272/// double-quotes to avoid misinterpreting them; see
273/// https://msdn.microsoft.com/en-us/library/dd9y37ha.aspx for NMake info,
274/// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
275/// for Windows file-naming info.
276static void PrintFilename(raw_ostream &OS, StringRef Filename,
277                          DependencyOutputFormat OutputFormat) {
278  // Convert filename to platform native path
279  llvm::SmallString<256> NativePath;
280  llvm::sys::path::native(Filename.str(), NativePath);
281
282  if (OutputFormat == DependencyOutputFormat::NMake) {
283    // Add quotes if needed. These are the characters listed as "special" to
284    // NMake, that are legal in a Windows filespec, and that could cause
285    // misinterpretation of the dependency string.
286    if (NativePath.find_first_of(" #${}^!") != StringRef::npos)
287      OS << '\"' << NativePath << '\"';
288    else
289      OS << NativePath;
290    return;
291  }
292  assert(OutputFormat == DependencyOutputFormat::Make);
293  for (unsigned i = 0, e = NativePath.size(); i != e; ++i) {
294    if (NativePath[i] == '#') // Handle '#' the broken gcc way.
295      OS << '\\';
296    else if (NativePath[i] == ' ') { // Handle space correctly.
297      OS << '\\';
298      unsigned j = i;
299      while (j > 0 && NativePath[--j] == '\\')
300        OS << '\\';
301    } else if (NativePath[i] == '$') // $ is escaped by $$.
302      OS << '$';
303    OS << NativePath[i];
304  }
305}
306
307void DependencyFileGenerator::outputDependencyFile(DiagnosticsEngine &Diags) {
308  if (SeenMissingHeader) {
309    llvm::sys::fs::remove(OutputFile);
310    return;
311  }
312
313  std::error_code EC;
314  llvm::raw_fd_ostream OS(OutputFile, EC, llvm::sys::fs::OF_Text);
315  if (EC) {
316    Diags.Report(diag::err_fe_error_opening) << OutputFile << EC.message();
317    return;
318  }
319
320  outputDependencyFile(OS);
321}
322
323void DependencyFileGenerator::outputDependencyFile(llvm::raw_ostream &OS) {
324  // Write out the dependency targets, trying to avoid overly long
325  // lines when possible. We try our best to emit exactly the same
326  // dependency file as GCC (4.2), assuming the included files are the
327  // same.
328  const unsigned MaxColumns = 75;
329  unsigned Columns = 0;
330
331  for (StringRef Target : Targets) {
332    unsigned N = Target.size();
333    if (Columns == 0) {
334      Columns += N;
335    } else if (Columns + N + 2 > MaxColumns) {
336      Columns = N + 2;
337      OS << " \\\n  ";
338    } else {
339      Columns += N + 1;
340      OS << ' ';
341    }
342    // Targets already quoted as needed.
343    OS << Target;
344  }
345
346  OS << ':';
347  Columns += 1;
348
349  // Now add each dependency in the order it was seen, but avoiding
350  // duplicates.
351  ArrayRef<std::string> Files = getDependencies();
352  for (StringRef File : Files) {
353    // Start a new line if this would exceed the column limit. Make
354    // sure to leave space for a trailing " \" in case we need to
355    // break the line on the next iteration.
356    unsigned N = File.size();
357    if (Columns + (N + 1) + 2 > MaxColumns) {
358      OS << " \\\n ";
359      Columns = 2;
360    }
361    OS << ' ';
362    PrintFilename(OS, File, OutputFormat);
363    Columns += N + 1;
364  }
365  OS << '\n';
366
367  // Create phony targets if requested.
368  if (PhonyTarget && !Files.empty()) {
369    unsigned Index = 0;
370    for (auto I = Files.begin(), E = Files.end(); I != E; ++I) {
371      if (Index++ == InputFileIndex)
372        continue;
373      OS << '\n';
374      PrintFilename(OS, *I, OutputFormat);
375      OS << ":\n";
376    }
377  }
378}
379