1 //===--- PrintPreprocessedOutput.cpp - Implement the -E mode --------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This code simply runs the preprocessor on the input file and prints out the
11 // result.  This is the traditional behavior of the -E option.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/Frontend/Utils.h"
16 #include "clang/Basic/Diagnostic.h"
17 #include "clang/Basic/SourceManager.h"
18 #include "clang/Frontend/PreprocessorOutputOptions.h"
19 #include "clang/Lex/MacroInfo.h"
20 #include "clang/Lex/PPCallbacks.h"
21 #include "clang/Lex/Pragma.h"
22 #include "clang/Lex/Preprocessor.h"
23 #include "clang/Lex/TokenConcatenation.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/SmallString.h"
26 #include "llvm/ADT/StringRef.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include <cctype>
30 #include <cstdio>
31 using namespace clang;
32 
33 /// PrintMacroDefinition - Print a macro definition in a form that will be
34 /// properly accepted back as a definition.
35 static void PrintMacroDefinition(const IdentifierInfo &II, const MacroInfo &MI,
36                                  Preprocessor &PP, raw_ostream &OS) {
37   OS << "#define " << II.getName();
38 
39   if (MI.isFunctionLike()) {
40     OS << '(';
41     if (!MI.arg_empty()) {
42       MacroInfo::arg_iterator AI = MI.arg_begin(), E = MI.arg_end();
43       for (; AI+1 != E; ++AI) {
44         OS << (*AI)->getName();
45         OS << ',';
46       }
47 
48       // Last argument.
49       if ((*AI)->getName() == "__VA_ARGS__")
50         OS << "...";
51       else
52         OS << (*AI)->getName();
53     }
54 
55     if (MI.isGNUVarargs())
56       OS << "...";  // #define foo(x...)
57 
58     OS << ')';
59   }
60 
61   // GCC always emits a space, even if the macro body is empty.  However, do not
62   // want to emit two spaces if the first token has a leading space.
63   if (MI.tokens_empty() || !MI.tokens_begin()->hasLeadingSpace())
64     OS << ' ';
65 
66   SmallString<128> SpellingBuffer;
67   for (MacroInfo::tokens_iterator I = MI.tokens_begin(), E = MI.tokens_end();
68        I != E; ++I) {
69     if (I->hasLeadingSpace())
70       OS << ' ';
71 
72     OS << PP.getSpelling(*I, SpellingBuffer);
73   }
74 }
75 
76 //===----------------------------------------------------------------------===//
77 // Preprocessed token printer
78 //===----------------------------------------------------------------------===//
79 
80 namespace {
81 class PrintPPOutputPPCallbacks : public PPCallbacks {
82   Preprocessor &PP;
83   SourceManager &SM;
84   TokenConcatenation ConcatInfo;
85 public:
86   raw_ostream &OS;
87 private:
88   unsigned CurLine;
89 
90   bool EmittedTokensOnThisLine;
91   bool EmittedDirectiveOnThisLine;
92   SrcMgr::CharacteristicKind FileType;
93   SmallString<512> CurFilename;
94   bool Initialized;
95   bool DisableLineMarkers;
96   bool DumpDefines;
97   bool UseLineDirective;
98   bool IsFirstFileEntered;
99 public:
100   PrintPPOutputPPCallbacks(Preprocessor &pp, raw_ostream &os,
101                            bool lineMarkers, bool defines)
102      : PP(pp), SM(PP.getSourceManager()),
103        ConcatInfo(PP), OS(os), DisableLineMarkers(lineMarkers),
104        DumpDefines(defines) {
105     CurLine = 0;
106     CurFilename += "<uninit>";
107     EmittedTokensOnThisLine = false;
108     EmittedDirectiveOnThisLine = false;
109     FileType = SrcMgr::C_User;
110     Initialized = false;
111     IsFirstFileEntered = false;
112 
113     // If we're in microsoft mode, use normal #line instead of line markers.
114     UseLineDirective = PP.getLangOpts().MicrosoftExt;
115   }
116 
117   void setEmittedTokensOnThisLine() { EmittedTokensOnThisLine = true; }
118   bool hasEmittedTokensOnThisLine() const { return EmittedTokensOnThisLine; }
119 
120   void setEmittedDirectiveOnThisLine() { EmittedDirectiveOnThisLine = true; }
121   bool hasEmittedDirectiveOnThisLine() const {
122     return EmittedDirectiveOnThisLine;
123   }
124 
125   bool startNewLineIfNeeded(bool ShouldUpdateCurrentLine = true);
126 
127   virtual void FileChanged(SourceLocation Loc, FileChangeReason Reason,
128                            SrcMgr::CharacteristicKind FileType,
129                            FileID PrevFID);
130   virtual void Ident(SourceLocation Loc, const std::string &str);
131   virtual void PragmaComment(SourceLocation Loc, const IdentifierInfo *Kind,
132                              const std::string &Str);
133   virtual void PragmaMessage(SourceLocation Loc, StringRef Str);
134   virtual void PragmaDiagnosticPush(SourceLocation Loc,
135                                     StringRef Namespace);
136   virtual void PragmaDiagnosticPop(SourceLocation Loc,
137                                    StringRef Namespace);
138   virtual void PragmaDiagnostic(SourceLocation Loc, StringRef Namespace,
139                                 diag::Mapping Map, StringRef Str);
140 
141   bool HandleFirstTokOnLine(Token &Tok);
142 
143   /// Move to the line of the provided source location. This will
144   /// return true if the output stream required adjustment or if
145   /// the requested location is on the first line.
146   bool MoveToLine(SourceLocation Loc) {
147     PresumedLoc PLoc = SM.getPresumedLoc(Loc);
148     if (PLoc.isInvalid())
149       return false;
150     return MoveToLine(PLoc.getLine()) || (PLoc.getLine() == 1);
151   }
152   bool MoveToLine(unsigned LineNo);
153 
154   bool AvoidConcat(const Token &PrevPrevTok, const Token &PrevTok,
155                    const Token &Tok) {
156     return ConcatInfo.AvoidConcat(PrevPrevTok, PrevTok, Tok);
157   }
158   void WriteLineInfo(unsigned LineNo, const char *Extra=0, unsigned ExtraLen=0);
159   bool LineMarkersAreDisabled() const { return DisableLineMarkers; }
160   void HandleNewlinesInToken(const char *TokStr, unsigned Len);
161 
162   /// MacroDefined - This hook is called whenever a macro definition is seen.
163   void MacroDefined(const Token &MacroNameTok, const MacroInfo *MI);
164 
165   /// MacroUndefined - This hook is called whenever a macro #undef is seen.
166   void MacroUndefined(const Token &MacroNameTok, const MacroInfo *MI);
167 };
168 }  // end anonymous namespace
169 
170 void PrintPPOutputPPCallbacks::WriteLineInfo(unsigned LineNo,
171                                              const char *Extra,
172                                              unsigned ExtraLen) {
173   startNewLineIfNeeded(/*ShouldUpdateCurrentLine=*/false);
174 
175   // Emit #line directives or GNU line markers depending on what mode we're in.
176   if (UseLineDirective) {
177     OS << "#line" << ' ' << LineNo << ' ' << '"';
178     OS.write(CurFilename.data(), CurFilename.size());
179     OS << '"';
180   } else {
181     OS << '#' << ' ' << LineNo << ' ' << '"';
182     OS.write(CurFilename.data(), CurFilename.size());
183     OS << '"';
184 
185     if (ExtraLen)
186       OS.write(Extra, ExtraLen);
187 
188     if (FileType == SrcMgr::C_System)
189       OS.write(" 3", 2);
190     else if (FileType == SrcMgr::C_ExternCSystem)
191       OS.write(" 3 4", 4);
192   }
193   OS << '\n';
194 }
195 
196 /// MoveToLine - Move the output to the source line specified by the location
197 /// object.  We can do this by emitting some number of \n's, or be emitting a
198 /// #line directive.  This returns false if already at the specified line, true
199 /// if some newlines were emitted.
200 bool PrintPPOutputPPCallbacks::MoveToLine(unsigned LineNo) {
201   // If this line is "close enough" to the original line, just print newlines,
202   // otherwise print a #line directive.
203   if (LineNo-CurLine <= 8) {
204     if (LineNo-CurLine == 1)
205       OS << '\n';
206     else if (LineNo == CurLine)
207       return false;    // Spelling line moved, but expansion line didn't.
208     else {
209       const char *NewLines = "\n\n\n\n\n\n\n\n";
210       OS.write(NewLines, LineNo-CurLine);
211     }
212   } else if (!DisableLineMarkers) {
213     // Emit a #line or line marker.
214     WriteLineInfo(LineNo, 0, 0);
215   } else {
216     // Okay, we're in -P mode, which turns off line markers.  However, we still
217     // need to emit a newline between tokens on different lines.
218     startNewLineIfNeeded(/*ShouldUpdateCurrentLine=*/false);
219   }
220 
221   CurLine = LineNo;
222   return true;
223 }
224 
225 bool
226 PrintPPOutputPPCallbacks::startNewLineIfNeeded(bool ShouldUpdateCurrentLine) {
227   if (EmittedTokensOnThisLine || EmittedDirectiveOnThisLine) {
228     OS << '\n';
229     EmittedTokensOnThisLine = false;
230     EmittedDirectiveOnThisLine = false;
231     if (ShouldUpdateCurrentLine)
232       ++CurLine;
233     return true;
234   }
235 
236   return false;
237 }
238 
239 /// FileChanged - Whenever the preprocessor enters or exits a #include file
240 /// it invokes this handler.  Update our conception of the current source
241 /// position.
242 void PrintPPOutputPPCallbacks::FileChanged(SourceLocation Loc,
243                                            FileChangeReason Reason,
244                                        SrcMgr::CharacteristicKind NewFileType,
245                                        FileID PrevFID) {
246   // Unless we are exiting a #include, make sure to skip ahead to the line the
247   // #include directive was at.
248   SourceManager &SourceMgr = SM;
249 
250   PresumedLoc UserLoc = SourceMgr.getPresumedLoc(Loc);
251   if (UserLoc.isInvalid())
252     return;
253 
254   unsigned NewLine = UserLoc.getLine();
255 
256   if (Reason == PPCallbacks::EnterFile) {
257     SourceLocation IncludeLoc = UserLoc.getIncludeLoc();
258     if (IncludeLoc.isValid())
259       MoveToLine(IncludeLoc);
260   } else if (Reason == PPCallbacks::SystemHeaderPragma) {
261     MoveToLine(NewLine);
262 
263     // TODO GCC emits the # directive for this directive on the line AFTER the
264     // directive and emits a bunch of spaces that aren't needed.  Emulate this
265     // strange behavior.
266   }
267 
268   CurLine = NewLine;
269 
270   CurFilename.clear();
271   CurFilename += UserLoc.getFilename();
272   Lexer::Stringify(CurFilename);
273   FileType = NewFileType;
274 
275   if (DisableLineMarkers) {
276     startNewLineIfNeeded(/*ShouldUpdateCurrentLine=*/false);
277     return;
278   }
279 
280   if (!Initialized) {
281     WriteLineInfo(CurLine);
282     Initialized = true;
283   }
284 
285   // Do not emit an enter marker for the main file (which we expect is the first
286   // entered file). This matches gcc, and improves compatibility with some tools
287   // which track the # line markers as a way to determine when the preprocessed
288   // output is in the context of the main file.
289   if (Reason == PPCallbacks::EnterFile && !IsFirstFileEntered) {
290     IsFirstFileEntered = true;
291     return;
292   }
293 
294   switch (Reason) {
295   case PPCallbacks::EnterFile:
296     WriteLineInfo(CurLine, " 1", 2);
297     break;
298   case PPCallbacks::ExitFile:
299     WriteLineInfo(CurLine, " 2", 2);
300     break;
301   case PPCallbacks::SystemHeaderPragma:
302   case PPCallbacks::RenameFile:
303     WriteLineInfo(CurLine);
304     break;
305   }
306 }
307 
308 /// Ident - Handle #ident directives when read by the preprocessor.
309 ///
310 void PrintPPOutputPPCallbacks::Ident(SourceLocation Loc, const std::string &S) {
311   MoveToLine(Loc);
312 
313   OS.write("#ident ", strlen("#ident "));
314   OS.write(&S[0], S.size());
315   EmittedTokensOnThisLine = true;
316 }
317 
318 /// MacroDefined - This hook is called whenever a macro definition is seen.
319 void PrintPPOutputPPCallbacks::MacroDefined(const Token &MacroNameTok,
320                                             const MacroInfo *MI) {
321   // Only print out macro definitions in -dD mode.
322   if (!DumpDefines ||
323       // Ignore __FILE__ etc.
324       MI->isBuiltinMacro()) return;
325 
326   MoveToLine(MI->getDefinitionLoc());
327   PrintMacroDefinition(*MacroNameTok.getIdentifierInfo(), *MI, PP, OS);
328   setEmittedDirectiveOnThisLine();
329 }
330 
331 void PrintPPOutputPPCallbacks::MacroUndefined(const Token &MacroNameTok,
332                                               const MacroInfo *MI) {
333   // Only print out macro definitions in -dD mode.
334   if (!DumpDefines) return;
335 
336   MoveToLine(MacroNameTok.getLocation());
337   OS << "#undef " << MacroNameTok.getIdentifierInfo()->getName();
338   setEmittedDirectiveOnThisLine();
339 }
340 
341 void PrintPPOutputPPCallbacks::PragmaComment(SourceLocation Loc,
342                                              const IdentifierInfo *Kind,
343                                              const std::string &Str) {
344   startNewLineIfNeeded();
345   MoveToLine(Loc);
346   OS << "#pragma comment(" << Kind->getName();
347 
348   if (!Str.empty()) {
349     OS << ", \"";
350 
351     for (unsigned i = 0, e = Str.size(); i != e; ++i) {
352       unsigned char Char = Str[i];
353       if (isprint(Char) && Char != '\\' && Char != '"')
354         OS << (char)Char;
355       else  // Output anything hard as an octal escape.
356         OS << '\\'
357            << (char)('0'+ ((Char >> 6) & 7))
358            << (char)('0'+ ((Char >> 3) & 7))
359            << (char)('0'+ ((Char >> 0) & 7));
360     }
361     OS << '"';
362   }
363 
364   OS << ')';
365   setEmittedDirectiveOnThisLine();
366 }
367 
368 void PrintPPOutputPPCallbacks::PragmaMessage(SourceLocation Loc,
369                                              StringRef Str) {
370   startNewLineIfNeeded();
371   MoveToLine(Loc);
372   OS << "#pragma message(";
373 
374   OS << '"';
375 
376   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
377     unsigned char Char = Str[i];
378     if (isprint(Char) && Char != '\\' && Char != '"')
379       OS << (char)Char;
380     else  // Output anything hard as an octal escape.
381       OS << '\\'
382          << (char)('0'+ ((Char >> 6) & 7))
383          << (char)('0'+ ((Char >> 3) & 7))
384          << (char)('0'+ ((Char >> 0) & 7));
385   }
386   OS << '"';
387 
388   OS << ')';
389   setEmittedDirectiveOnThisLine();
390 }
391 
392 void PrintPPOutputPPCallbacks::
393 PragmaDiagnosticPush(SourceLocation Loc, StringRef Namespace) {
394   startNewLineIfNeeded();
395   MoveToLine(Loc);
396   OS << "#pragma " << Namespace << " diagnostic push";
397   setEmittedDirectiveOnThisLine();
398 }
399 
400 void PrintPPOutputPPCallbacks::
401 PragmaDiagnosticPop(SourceLocation Loc, StringRef Namespace) {
402   startNewLineIfNeeded();
403   MoveToLine(Loc);
404   OS << "#pragma " << Namespace << " diagnostic pop";
405   setEmittedDirectiveOnThisLine();
406 }
407 
408 void PrintPPOutputPPCallbacks::
409 PragmaDiagnostic(SourceLocation Loc, StringRef Namespace,
410                  diag::Mapping Map, StringRef Str) {
411   startNewLineIfNeeded();
412   MoveToLine(Loc);
413   OS << "#pragma " << Namespace << " diagnostic ";
414   switch (Map) {
415   case diag::MAP_WARNING:
416     OS << "warning";
417     break;
418   case diag::MAP_ERROR:
419     OS << "error";
420     break;
421   case diag::MAP_IGNORE:
422     OS << "ignored";
423     break;
424   case diag::MAP_FATAL:
425     OS << "fatal";
426     break;
427   }
428   OS << " \"" << Str << '"';
429   setEmittedDirectiveOnThisLine();
430 }
431 
432 /// HandleFirstTokOnLine - When emitting a preprocessed file in -E mode, this
433 /// is called for the first token on each new line.  If this really is the start
434 /// of a new logical line, handle it and return true, otherwise return false.
435 /// This may not be the start of a logical line because the "start of line"
436 /// marker is set for spelling lines, not expansion ones.
437 bool PrintPPOutputPPCallbacks::HandleFirstTokOnLine(Token &Tok) {
438   // Figure out what line we went to and insert the appropriate number of
439   // newline characters.
440   if (!MoveToLine(Tok.getLocation()))
441     return false;
442 
443   // Print out space characters so that the first token on a line is
444   // indented for easy reading.
445   unsigned ColNo = SM.getExpansionColumnNumber(Tok.getLocation());
446 
447   // This hack prevents stuff like:
448   // #define HASH #
449   // HASH define foo bar
450   // From having the # character end up at column 1, which makes it so it
451   // is not handled as a #define next time through the preprocessor if in
452   // -fpreprocessed mode.
453   if (ColNo <= 1 && Tok.is(tok::hash))
454     OS << ' ';
455 
456   // Otherwise, indent the appropriate number of spaces.
457   for (; ColNo > 1; --ColNo)
458     OS << ' ';
459 
460   return true;
461 }
462 
463 void PrintPPOutputPPCallbacks::HandleNewlinesInToken(const char *TokStr,
464                                                      unsigned Len) {
465   unsigned NumNewlines = 0;
466   for (; Len; --Len, ++TokStr) {
467     if (*TokStr != '\n' &&
468         *TokStr != '\r')
469       continue;
470 
471     ++NumNewlines;
472 
473     // If we have \n\r or \r\n, skip both and count as one line.
474     if (Len != 1 &&
475         (TokStr[1] == '\n' || TokStr[1] == '\r') &&
476         TokStr[0] != TokStr[1])
477       ++TokStr, --Len;
478   }
479 
480   if (NumNewlines == 0) return;
481 
482   CurLine += NumNewlines;
483 }
484 
485 
486 namespace {
487 struct UnknownPragmaHandler : public PragmaHandler {
488   const char *Prefix;
489   PrintPPOutputPPCallbacks *Callbacks;
490 
491   UnknownPragmaHandler(const char *prefix, PrintPPOutputPPCallbacks *callbacks)
492     : Prefix(prefix), Callbacks(callbacks) {}
493   virtual void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
494                             Token &PragmaTok) {
495     // Figure out what line we went to and insert the appropriate number of
496     // newline characters.
497     Callbacks->startNewLineIfNeeded();
498     Callbacks->MoveToLine(PragmaTok.getLocation());
499     Callbacks->OS.write(Prefix, strlen(Prefix));
500     // Read and print all of the pragma tokens.
501     while (PragmaTok.isNot(tok::eod)) {
502       if (PragmaTok.hasLeadingSpace())
503         Callbacks->OS << ' ';
504       std::string TokSpell = PP.getSpelling(PragmaTok);
505       Callbacks->OS.write(&TokSpell[0], TokSpell.size());
506       PP.LexUnexpandedToken(PragmaTok);
507     }
508     Callbacks->setEmittedDirectiveOnThisLine();
509   }
510 };
511 } // end anonymous namespace
512 
513 
514 static void PrintPreprocessedTokens(Preprocessor &PP, Token &Tok,
515                                     PrintPPOutputPPCallbacks *Callbacks,
516                                     raw_ostream &OS) {
517   char Buffer[256];
518   Token PrevPrevTok, PrevTok;
519   PrevPrevTok.startToken();
520   PrevTok.startToken();
521   while (1) {
522     if (Callbacks->hasEmittedDirectiveOnThisLine()) {
523       Callbacks->startNewLineIfNeeded();
524       Callbacks->MoveToLine(Tok.getLocation());
525     }
526 
527     // If this token is at the start of a line, emit newlines if needed.
528     if (Tok.isAtStartOfLine() && Callbacks->HandleFirstTokOnLine(Tok)) {
529       // done.
530     } else if (Tok.hasLeadingSpace() ||
531                // If we haven't emitted a token on this line yet, PrevTok isn't
532                // useful to look at and no concatenation could happen anyway.
533                (Callbacks->hasEmittedTokensOnThisLine() &&
534                 // Don't print "-" next to "-", it would form "--".
535                 Callbacks->AvoidConcat(PrevPrevTok, PrevTok, Tok))) {
536       OS << ' ';
537     }
538 
539     if (IdentifierInfo *II = Tok.getIdentifierInfo()) {
540       OS << II->getName();
541     } else if (Tok.isLiteral() && !Tok.needsCleaning() &&
542                Tok.getLiteralData()) {
543       OS.write(Tok.getLiteralData(), Tok.getLength());
544     } else if (Tok.getLength() < 256) {
545       const char *TokPtr = Buffer;
546       unsigned Len = PP.getSpelling(Tok, TokPtr);
547       OS.write(TokPtr, Len);
548 
549       // Tokens that can contain embedded newlines need to adjust our current
550       // line number.
551       if (Tok.getKind() == tok::comment)
552         Callbacks->HandleNewlinesInToken(TokPtr, Len);
553     } else {
554       std::string S = PP.getSpelling(Tok);
555       OS.write(&S[0], S.size());
556 
557       // Tokens that can contain embedded newlines need to adjust our current
558       // line number.
559       if (Tok.getKind() == tok::comment)
560         Callbacks->HandleNewlinesInToken(&S[0], S.size());
561     }
562     Callbacks->setEmittedTokensOnThisLine();
563 
564     if (Tok.is(tok::eof)) break;
565 
566     PrevPrevTok = PrevTok;
567     PrevTok = Tok;
568     PP.Lex(Tok);
569   }
570 }
571 
572 typedef std::pair<const IdentifierInfo *, MacroInfo *> id_macro_pair;
573 static int MacroIDCompare(const void* a, const void* b) {
574   const id_macro_pair *LHS = static_cast<const id_macro_pair*>(a);
575   const id_macro_pair *RHS = static_cast<const id_macro_pair*>(b);
576   return LHS->first->getName().compare(RHS->first->getName());
577 }
578 
579 static void DoPrintMacros(Preprocessor &PP, raw_ostream *OS) {
580   // Ignore unknown pragmas.
581   PP.AddPragmaHandler(new EmptyPragmaHandler());
582 
583   // -dM mode just scans and ignores all tokens in the files, then dumps out
584   // the macro table at the end.
585   PP.EnterMainSourceFile();
586 
587   Token Tok;
588   do PP.Lex(Tok);
589   while (Tok.isNot(tok::eof));
590 
591   SmallVector<id_macro_pair, 128> MacrosByID;
592   for (Preprocessor::macro_iterator I = PP.macro_begin(), E = PP.macro_end();
593        I != E; ++I) {
594     if (I->first->hasMacroDefinition())
595       MacrosByID.push_back(id_macro_pair(I->first, I->second));
596   }
597   llvm::array_pod_sort(MacrosByID.begin(), MacrosByID.end(), MacroIDCompare);
598 
599   for (unsigned i = 0, e = MacrosByID.size(); i != e; ++i) {
600     MacroInfo &MI = *MacrosByID[i].second;
601     // Ignore computed macros like __LINE__ and friends.
602     if (MI.isBuiltinMacro()) continue;
603 
604     PrintMacroDefinition(*MacrosByID[i].first, MI, PP, *OS);
605     *OS << '\n';
606   }
607 }
608 
609 /// DoPrintPreprocessedInput - This implements -E mode.
610 ///
611 void clang::DoPrintPreprocessedInput(Preprocessor &PP, raw_ostream *OS,
612                                      const PreprocessorOutputOptions &Opts) {
613   // Show macros with no output is handled specially.
614   if (!Opts.ShowCPP) {
615     assert(Opts.ShowMacros && "Not yet implemented!");
616     DoPrintMacros(PP, OS);
617     return;
618   }
619 
620   // Inform the preprocessor whether we want it to retain comments or not, due
621   // to -C or -CC.
622   PP.SetCommentRetentionState(Opts.ShowComments, Opts.ShowMacroComments);
623 
624   PrintPPOutputPPCallbacks *Callbacks =
625       new PrintPPOutputPPCallbacks(PP, *OS, !Opts.ShowLineMarkers,
626                                    Opts.ShowMacros);
627   PP.AddPragmaHandler(new UnknownPragmaHandler("#pragma", Callbacks));
628   PP.AddPragmaHandler("GCC", new UnknownPragmaHandler("#pragma GCC",Callbacks));
629   PP.AddPragmaHandler("clang",
630                       new UnknownPragmaHandler("#pragma clang", Callbacks));
631 
632   PP.addPPCallbacks(Callbacks);
633 
634   // After we have configured the preprocessor, enter the main file.
635   PP.EnterMainSourceFile();
636 
637   // Consume all of the tokens that come from the predefines buffer.  Those
638   // should not be emitted into the output and are guaranteed to be at the
639   // start.
640   const SourceManager &SourceMgr = PP.getSourceManager();
641   Token Tok;
642   do {
643     PP.Lex(Tok);
644     if (Tok.is(tok::eof) || !Tok.getLocation().isFileID())
645       break;
646 
647     PresumedLoc PLoc = SourceMgr.getPresumedLoc(Tok.getLocation());
648     if (PLoc.isInvalid())
649       break;
650 
651     if (strcmp(PLoc.getFilename(), "<built-in>"))
652       break;
653   } while (true);
654 
655   // Read all the preprocessed tokens, printing them out to the stream.
656   PrintPreprocessedTokens(PP, Tok, Callbacks, *OS);
657   *OS << '\n';
658 }
659