FormatString.cpp revision 8be066e6733364cd34f25c4f7b7344f72aa23369 
1// FormatString.cpp - Common stuff for handling printf/scanf formats -*- C++ -*-
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// Shared details for processing format strings of printf and scanf
11// (and friends).
12//
13//===----------------------------------------------------------------------===//
14
15#include "FormatStringParsing.h"
16#include "clang/Basic/LangOptions.h"
17#include "clang/Basic/TargetInfo.h"
18
19using clang::analyze_format_string::ArgType;
20using clang::analyze_format_string::FormatStringHandler;
21using clang::analyze_format_string::FormatSpecifier;
22using clang::analyze_format_string::LengthModifier;
23using clang::analyze_format_string::OptionalAmount;
24using clang::analyze_format_string::PositionContext;
25using clang::analyze_format_string::ConversionSpecifier;
26using namespace clang;
27
28// Key function to FormatStringHandler.
29FormatStringHandler::~FormatStringHandler() {}
30
31//===----------------------------------------------------------------------===//
32// Functions for parsing format strings components in both printf and
33// scanf format strings.
34//===----------------------------------------------------------------------===//
35
36OptionalAmount
37clang::analyze_format_string::ParseAmount(const char *&Beg, const char *E) {
38  const char *I = Beg;
39  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
40
41  unsigned accumulator = 0;
42  bool hasDigits = false;
43
44  for ( ; I != E; ++I) {
45    char c = *I;
46    if (c >= '0' && c <= '9') {
47      hasDigits = true;
48      accumulator = (accumulator * 10) + (c - '0');
49      continue;
50    }
51
52    if (hasDigits)
53      return OptionalAmount(OptionalAmount::Constant, accumulator, Beg, I - Beg,
54          false);
55
56    break;
57  }
58
59  return OptionalAmount();
60}
61
62OptionalAmount
63clang::analyze_format_string::ParseNonPositionAmount(const char *&Beg,
64                                                     const char *E,
65                                                     unsigned &argIndex) {
66  if (*Beg == '*') {
67    ++Beg;
68    return OptionalAmount(OptionalAmount::Arg, argIndex++, Beg, 0, false);
69  }
70
71  return ParseAmount(Beg, E);
72}
73
74OptionalAmount
75clang::analyze_format_string::ParsePositionAmount(FormatStringHandler &H,
76                                                  const char *Start,
77                                                  const char *&Beg,
78                                                  const char *E,
79                                                  PositionContext p) {
80  if (*Beg == '*') {
81    const char *I = Beg + 1;
82    const OptionalAmount &Amt = ParseAmount(I, E);
83
84    if (Amt.getHowSpecified() == OptionalAmount::NotSpecified) {
85      H.HandleInvalidPosition(Beg, I - Beg, p);
86      return OptionalAmount(false);
87    }
88
89    if (I == E) {
90      // No more characters left?
91      H.HandleIncompleteSpecifier(Start, E - Start);
92      return OptionalAmount(false);
93    }
94
95    assert(Amt.getHowSpecified() == OptionalAmount::Constant);
96
97    if (*I == '$') {
98      // Handle positional arguments
99
100      // Special case: '*0$', since this is an easy mistake.
101      if (Amt.getConstantAmount() == 0) {
102        H.HandleZeroPosition(Beg, I - Beg + 1);
103        return OptionalAmount(false);
104      }
105
106      const char *Tmp = Beg;
107      Beg = ++I;
108
109      return OptionalAmount(OptionalAmount::Arg, Amt.getConstantAmount() - 1,
110                            Tmp, 0, true);
111    }
112
113    H.HandleInvalidPosition(Beg, I - Beg, p);
114    return OptionalAmount(false);
115  }
116
117  return ParseAmount(Beg, E);
118}
119
120
121bool
122clang::analyze_format_string::ParseFieldWidth(FormatStringHandler &H,
123                                              FormatSpecifier &CS,
124                                              const char *Start,
125                                              const char *&Beg, const char *E,
126                                              unsigned *argIndex) {
127  // FIXME: Support negative field widths.
128  if (argIndex) {
129    CS.setFieldWidth(ParseNonPositionAmount(Beg, E, *argIndex));
130  }
131  else {
132    const OptionalAmount Amt =
133      ParsePositionAmount(H, Start, Beg, E,
134                          analyze_format_string::FieldWidthPos);
135
136    if (Amt.isInvalid())
137      return true;
138    CS.setFieldWidth(Amt);
139  }
140  return false;
141}
142
143bool
144clang::analyze_format_string::ParseArgPosition(FormatStringHandler &H,
145                                               FormatSpecifier &FS,
146                                               const char *Start,
147                                               const char *&Beg,
148                                               const char *E) {
149  const char *I = Beg;
150
151  const OptionalAmount &Amt = ParseAmount(I, E);
152
153  if (I == E) {
154    // No more characters left?
155    H.HandleIncompleteSpecifier(Start, E - Start);
156    return true;
157  }
158
159  if (Amt.getHowSpecified() == OptionalAmount::Constant && *(I++) == '$') {
160    // Warn that positional arguments are non-standard.
161    H.HandlePosition(Start, I - Start);
162
163    // Special case: '%0$', since this is an easy mistake.
164    if (Amt.getConstantAmount() == 0) {
165      H.HandleZeroPosition(Start, I - Start);
166      return true;
167    }
168
169    FS.setArgIndex(Amt.getConstantAmount() - 1);
170    FS.setUsesPositionalArg();
171    // Update the caller's pointer if we decided to consume
172    // these characters.
173    Beg = I;
174    return false;
175  }
176
177  return false;
178}
179
180bool
181clang::analyze_format_string::ParseLengthModifier(FormatSpecifier &FS,
182                                                  const char *&I,
183                                                  const char *E,
184                                                  const LangOptions &LO,
185                                                  bool IsScanf) {
186  LengthModifier::Kind lmKind = LengthModifier::None;
187  const char *lmPosition = I;
188  switch (*I) {
189    default:
190      return false;
191    case 'h':
192      ++I;
193      lmKind = (I != E && *I == 'h') ? (++I, LengthModifier::AsChar)
194                                     : LengthModifier::AsShort;
195      break;
196    case 'l':
197      ++I;
198      lmKind = (I != E && *I == 'l') ? (++I, LengthModifier::AsLongLong)
199                                     : LengthModifier::AsLong;
200      break;
201    case 'j': lmKind = LengthModifier::AsIntMax;     ++I; break;
202    case 'z': lmKind = LengthModifier::AsSizeT;      ++I; break;
203    case 't': lmKind = LengthModifier::AsPtrDiff;    ++I; break;
204    case 'L': lmKind = LengthModifier::AsLongDouble; ++I; break;
205    case 'q': lmKind = LengthModifier::AsQuad;       ++I; break;
206    case 'a':
207      if (IsScanf && !LO.C99 && !LO.CPlusPlus0x) {
208        // For scanf in C90, look at the next character to see if this should
209        // be parsed as the GNU extension 'a' length modifier. If not, this
210        // will be parsed as a conversion specifier.
211        ++I;
212        if (I != E && (*I == 's' || *I == 'S' || *I == '[')) {
213          lmKind = LengthModifier::AsAllocate;
214          break;
215        }
216        --I;
217      }
218      return false;
219    case 'm':
220      if (IsScanf) {
221        lmKind = LengthModifier::AsMAllocate;
222        ++I;
223        break;
224      }
225      return false;
226  }
227  LengthModifier lm(lmPosition, lmKind);
228  FS.setLengthModifier(lm);
229  return true;
230}
231
232//===----------------------------------------------------------------------===//
233// Methods on ArgType.
234//===----------------------------------------------------------------------===//
235
236bool ArgType::matchesType(ASTContext &C, QualType argTy) const {
237  if (Ptr) {
238    // It has to be a pointer.
239    const PointerType *PT = argTy->getAs<PointerType>();
240    if (!PT)
241      return false;
242
243    // We cannot write through a const qualified pointer.
244    if (PT->getPointeeType().isConstQualified())
245      return false;
246
247    argTy = PT->getPointeeType();
248  }
249
250  switch (K) {
251    case InvalidTy:
252      llvm_unreachable("ArgType must be valid");
253
254    case UnknownTy:
255      return true;
256
257    case AnyCharTy: {
258      if (const EnumType *ETy = argTy->getAs<EnumType>())
259        argTy = ETy->getDecl()->getIntegerType();
260
261      if (const BuiltinType *BT = argTy->getAs<BuiltinType>())
262        switch (BT->getKind()) {
263          default:
264            break;
265          case BuiltinType::Char_S:
266          case BuiltinType::SChar:
267          case BuiltinType::UChar:
268          case BuiltinType::Char_U:
269            return true;
270        }
271      return false;
272    }
273
274    case SpecificTy: {
275      if (const EnumType *ETy = argTy->getAs<EnumType>())
276        argTy = ETy->getDecl()->getIntegerType();
277      argTy = C.getCanonicalType(argTy).getUnqualifiedType();
278
279      if (T == argTy)
280        return true;
281      // Check for "compatible types".
282      if (const BuiltinType *BT = argTy->getAs<BuiltinType>())
283        switch (BT->getKind()) {
284          default:
285            break;
286          case BuiltinType::Char_S:
287          case BuiltinType::SChar:
288          case BuiltinType::Char_U:
289          case BuiltinType::UChar:
290            return T == C.UnsignedCharTy || T == C.SignedCharTy;
291          case BuiltinType::Short:
292            return T == C.UnsignedShortTy;
293          case BuiltinType::UShort:
294            return T == C.ShortTy;
295          case BuiltinType::Int:
296            return T == C.UnsignedIntTy;
297          case BuiltinType::UInt:
298            return T == C.IntTy;
299          case BuiltinType::Long:
300            return T == C.UnsignedLongTy;
301          case BuiltinType::ULong:
302            return T == C.LongTy;
303          case BuiltinType::LongLong:
304            return T == C.UnsignedLongLongTy;
305          case BuiltinType::ULongLong:
306            return T == C.LongLongTy;
307        }
308      return false;
309    }
310
311    case CStrTy: {
312      const PointerType *PT = argTy->getAs<PointerType>();
313      if (!PT)
314        return false;
315      QualType pointeeTy = PT->getPointeeType();
316      if (const BuiltinType *BT = pointeeTy->getAs<BuiltinType>())
317        switch (BT->getKind()) {
318          case BuiltinType::Void:
319          case BuiltinType::Char_U:
320          case BuiltinType::UChar:
321          case BuiltinType::Char_S:
322          case BuiltinType::SChar:
323            return true;
324          default:
325            break;
326        }
327
328      return false;
329    }
330
331    case WCStrTy: {
332      const PointerType *PT = argTy->getAs<PointerType>();
333      if (!PT)
334        return false;
335      QualType pointeeTy =
336        C.getCanonicalType(PT->getPointeeType()).getUnqualifiedType();
337      return pointeeTy == C.getWCharType();
338    }
339
340    case WIntTy: {
341
342      QualType PromoArg =
343        argTy->isPromotableIntegerType()
344          ? C.getPromotedIntegerType(argTy) : argTy;
345
346      QualType WInt = C.getCanonicalType(C.getWIntType()).getUnqualifiedType();
347      PromoArg = C.getCanonicalType(PromoArg).getUnqualifiedType();
348
349      // If the promoted argument is the corresponding signed type of the
350      // wint_t type, then it should match.
351      if (PromoArg->hasSignedIntegerRepresentation() &&
352          C.getCorrespondingUnsignedType(PromoArg) == WInt)
353        return true;
354
355      return WInt == PromoArg;
356    }
357
358    case CPointerTy:
359      return argTy->isPointerType() || argTy->isObjCObjectPointerType() ||
360             argTy->isBlockPointerType() || argTy->isNullPtrType();
361
362    case ObjCPointerTy: {
363      if (argTy->getAs<ObjCObjectPointerType>() ||
364          argTy->getAs<BlockPointerType>())
365        return true;
366
367      // Handle implicit toll-free bridging.
368      if (const PointerType *PT = argTy->getAs<PointerType>()) {
369        // Things such as CFTypeRef are really just opaque pointers
370        // to C structs representing CF types that can often be bridged
371        // to Objective-C objects.  Since the compiler doesn't know which
372        // structs can be toll-free bridged, we just accept them all.
373        QualType pointee = PT->getPointeeType();
374        if (pointee->getAsStructureType() || pointee->isVoidType())
375          return true;
376      }
377      return false;
378    }
379  }
380
381  llvm_unreachable("Invalid ArgType Kind!");
382}
383
384QualType ArgType::getRepresentativeType(ASTContext &C) const {
385  QualType Res;
386  switch (K) {
387    case InvalidTy:
388      llvm_unreachable("No representative type for Invalid ArgType");
389    case UnknownTy:
390      llvm_unreachable("No representative type for Unknown ArgType");
391    case AnyCharTy:
392      Res = C.CharTy;
393      break;
394    case SpecificTy:
395      Res = T;
396      break;
397    case CStrTy:
398      Res = C.getPointerType(C.CharTy);
399      break;
400    case WCStrTy:
401      Res = C.getPointerType(C.getWCharType());
402      break;
403    case ObjCPointerTy:
404      Res = C.ObjCBuiltinIdTy;
405      break;
406    case CPointerTy:
407      Res = C.VoidPtrTy;
408      break;
409    case WIntTy: {
410      Res = C.getWIntType();
411      break;
412    }
413  }
414
415  if (Ptr)
416    Res = C.getPointerType(Res);
417  return Res;
418}
419
420std::string ArgType::getRepresentativeTypeName(ASTContext &C) const {
421  std::string S = getRepresentativeType(C).getAsString();
422
423  std::string Alias;
424  if (Name) {
425    // Use a specific name for this type, e.g. "size_t".
426    Alias = Name;
427    if (Ptr) {
428      // If ArgType is actually a pointer to T, append an asterisk.
429      Alias += (Alias[Alias.size()-1] == '*') ? "*" : " *";
430    }
431    // If Alias is the same as the underlying type, e.g. wchar_t, then drop it.
432    if (S == Alias)
433      Alias.clear();
434  }
435
436  if (!Alias.empty())
437    return std::string("'") + Alias + "' (aka '" + S + "')";
438  return std::string("'") + S + "'";
439}
440
441
442//===----------------------------------------------------------------------===//
443// Methods on OptionalAmount.
444//===----------------------------------------------------------------------===//
445
446ArgType
447analyze_format_string::OptionalAmount::getArgType(ASTContext &Ctx) const {
448  return Ctx.IntTy;
449}
450
451//===----------------------------------------------------------------------===//
452// Methods on LengthModifier.
453//===----------------------------------------------------------------------===//
454
455const char *
456analyze_format_string::LengthModifier::toString() const {
457  switch (kind) {
458  case AsChar:
459    return "hh";
460  case AsShort:
461    return "h";
462  case AsLong: // or AsWideChar
463    return "l";
464  case AsLongLong:
465    return "ll";
466  case AsQuad:
467    return "q";
468  case AsIntMax:
469    return "j";
470  case AsSizeT:
471    return "z";
472  case AsPtrDiff:
473    return "t";
474  case AsLongDouble:
475    return "L";
476  case AsAllocate:
477    return "a";
478  case AsMAllocate:
479    return "m";
480  case None:
481    return "";
482  }
483  return NULL;
484}
485
486//===----------------------------------------------------------------------===//
487// Methods on ConversionSpecifier.
488//===----------------------------------------------------------------------===//
489
490const char *ConversionSpecifier::toString() const {
491  switch (kind) {
492  case dArg: return "d";
493  case iArg: return "i";
494  case oArg: return "o";
495  case uArg: return "u";
496  case xArg: return "x";
497  case XArg: return "X";
498  case fArg: return "f";
499  case FArg: return "F";
500  case eArg: return "e";
501  case EArg: return "E";
502  case gArg: return "g";
503  case GArg: return "G";
504  case aArg: return "a";
505  case AArg: return "A";
506  case cArg: return "c";
507  case sArg: return "s";
508  case pArg: return "p";
509  case nArg: return "n";
510  case PercentArg:  return "%";
511  case ScanListArg: return "[";
512  case InvalidSpecifier: return NULL;
513
514  // MacOS X unicode extensions.
515  case CArg: return "C";
516  case SArg: return "S";
517
518  // Objective-C specific specifiers.
519  case ObjCObjArg: return "@";
520
521  // GlibC specific specifiers.
522  case PrintErrno: return "m";
523  }
524  return NULL;
525}
526
527//===----------------------------------------------------------------------===//
528// Methods on OptionalAmount.
529//===----------------------------------------------------------------------===//
530
531void OptionalAmount::toString(raw_ostream &os) const {
532  switch (hs) {
533  case Invalid:
534  case NotSpecified:
535    return;
536  case Arg:
537    if (UsesDotPrefix)
538        os << ".";
539    if (usesPositionalArg())
540      os << "*" << getPositionalArgIndex() << "$";
541    else
542      os << "*";
543    break;
544  case Constant:
545    if (UsesDotPrefix)
546        os << ".";
547    os << amt;
548    break;
549  }
550}
551
552bool FormatSpecifier::hasValidLengthModifier(const TargetInfo &Target) const {
553  switch (LM.getKind()) {
554    case LengthModifier::None:
555      return true;
556
557    // Handle most integer flags
558    case LengthModifier::AsChar:
559    case LengthModifier::AsShort:
560    case LengthModifier::AsLongLong:
561    case LengthModifier::AsQuad:
562    case LengthModifier::AsIntMax:
563    case LengthModifier::AsSizeT:
564    case LengthModifier::AsPtrDiff:
565      switch (CS.getKind()) {
566        case ConversionSpecifier::dArg:
567        case ConversionSpecifier::iArg:
568        case ConversionSpecifier::oArg:
569        case ConversionSpecifier::uArg:
570        case ConversionSpecifier::xArg:
571        case ConversionSpecifier::XArg:
572        case ConversionSpecifier::nArg:
573          return true;
574        default:
575          return false;
576      }
577
578    // Handle 'l' flag
579    case LengthModifier::AsLong:
580      switch (CS.getKind()) {
581        case ConversionSpecifier::dArg:
582        case ConversionSpecifier::iArg:
583        case ConversionSpecifier::oArg:
584        case ConversionSpecifier::uArg:
585        case ConversionSpecifier::xArg:
586        case ConversionSpecifier::XArg:
587        case ConversionSpecifier::aArg:
588        case ConversionSpecifier::AArg:
589        case ConversionSpecifier::fArg:
590        case ConversionSpecifier::FArg:
591        case ConversionSpecifier::eArg:
592        case ConversionSpecifier::EArg:
593        case ConversionSpecifier::gArg:
594        case ConversionSpecifier::GArg:
595        case ConversionSpecifier::nArg:
596        case ConversionSpecifier::cArg:
597        case ConversionSpecifier::sArg:
598        case ConversionSpecifier::ScanListArg:
599          return true;
600        default:
601          return false;
602      }
603
604    case LengthModifier::AsLongDouble:
605      switch (CS.getKind()) {
606        case ConversionSpecifier::aArg:
607        case ConversionSpecifier::AArg:
608        case ConversionSpecifier::fArg:
609        case ConversionSpecifier::FArg:
610        case ConversionSpecifier::eArg:
611        case ConversionSpecifier::EArg:
612        case ConversionSpecifier::gArg:
613        case ConversionSpecifier::GArg:
614          return true;
615        // GNU libc extension.
616        case ConversionSpecifier::dArg:
617        case ConversionSpecifier::iArg:
618        case ConversionSpecifier::oArg:
619        case ConversionSpecifier::uArg:
620        case ConversionSpecifier::xArg:
621        case ConversionSpecifier::XArg:
622          return !Target.getTriple().isOSDarwin() &&
623                 !Target.getTriple().isOSWindows();
624        default:
625          return false;
626      }
627
628    case LengthModifier::AsAllocate:
629      switch (CS.getKind()) {
630        case ConversionSpecifier::sArg:
631        case ConversionSpecifier::SArg:
632        case ConversionSpecifier::ScanListArg:
633          return true;
634        default:
635          return false;
636      }
637
638    case LengthModifier::AsMAllocate:
639      switch (CS.getKind()) {
640        case ConversionSpecifier::cArg:
641        case ConversionSpecifier::CArg:
642        case ConversionSpecifier::sArg:
643        case ConversionSpecifier::SArg:
644        case ConversionSpecifier::ScanListArg:
645          return true;
646        default:
647          return false;
648      }
649  }
650  llvm_unreachable("Invalid LengthModifier Kind!");
651}
652
653bool FormatSpecifier::hasStandardLengthModifier() const {
654  switch (LM.getKind()) {
655    case LengthModifier::None:
656    case LengthModifier::AsChar:
657    case LengthModifier::AsShort:
658    case LengthModifier::AsLong:
659    case LengthModifier::AsLongLong:
660    case LengthModifier::AsIntMax:
661    case LengthModifier::AsSizeT:
662    case LengthModifier::AsPtrDiff:
663    case LengthModifier::AsLongDouble:
664      return true;
665    case LengthModifier::AsAllocate:
666    case LengthModifier::AsMAllocate:
667    case LengthModifier::AsQuad:
668      return false;
669  }
670  llvm_unreachable("Invalid LengthModifier Kind!");
671}
672
673bool FormatSpecifier::hasStandardConversionSpecifier(const LangOptions &LangOpt) const {
674  switch (CS.getKind()) {
675    case ConversionSpecifier::cArg:
676    case ConversionSpecifier::dArg:
677    case ConversionSpecifier::iArg:
678    case ConversionSpecifier::oArg:
679    case ConversionSpecifier::uArg:
680    case ConversionSpecifier::xArg:
681    case ConversionSpecifier::XArg:
682    case ConversionSpecifier::fArg:
683    case ConversionSpecifier::FArg:
684    case ConversionSpecifier::eArg:
685    case ConversionSpecifier::EArg:
686    case ConversionSpecifier::gArg:
687    case ConversionSpecifier::GArg:
688    case ConversionSpecifier::aArg:
689    case ConversionSpecifier::AArg:
690    case ConversionSpecifier::sArg:
691    case ConversionSpecifier::pArg:
692    case ConversionSpecifier::nArg:
693    case ConversionSpecifier::ObjCObjArg:
694    case ConversionSpecifier::ScanListArg:
695    case ConversionSpecifier::PercentArg:
696      return true;
697    case ConversionSpecifier::CArg:
698    case ConversionSpecifier::SArg:
699      return LangOpt.ObjC1 || LangOpt.ObjC2;
700    case ConversionSpecifier::InvalidSpecifier:
701    case ConversionSpecifier::PrintErrno:
702      return false;
703  }
704  llvm_unreachable("Invalid ConversionSpecifier Kind!");
705}
706
707bool FormatSpecifier::hasStandardLengthConversionCombination() const {
708  if (LM.getKind() == LengthModifier::AsLongDouble) {
709    switch(CS.getKind()) {
710        case ConversionSpecifier::dArg:
711        case ConversionSpecifier::iArg:
712        case ConversionSpecifier::oArg:
713        case ConversionSpecifier::uArg:
714        case ConversionSpecifier::xArg:
715        case ConversionSpecifier::XArg:
716          return false;
717        default:
718          return true;
719    }
720  }
721  return true;
722}
723
724llvm::Optional<LengthModifier>
725FormatSpecifier::getCorrectedLengthModifier() const {
726  if (CS.isAnyIntArg() || CS.getKind() == ConversionSpecifier::nArg) {
727    if (LM.getKind() == LengthModifier::AsLongDouble ||
728        LM.getKind() == LengthModifier::AsQuad) {
729      LengthModifier FixedLM(LM);
730      FixedLM.setKind(LengthModifier::AsLongLong);
731      return FixedLM;
732    }
733  }
734
735  return llvm::Optional<LengthModifier>();
736}
737
738bool FormatSpecifier::namedTypeToLengthModifier(QualType QT,
739                                                LengthModifier &LM) {
740  assert(isa<TypedefType>(QT) && "Expected a TypedefType");
741  const TypedefNameDecl *Typedef = cast<TypedefType>(QT)->getDecl();
742
743  for (;;) {
744    const IdentifierInfo *Identifier = Typedef->getIdentifier();
745    if (Identifier->getName() == "size_t") {
746      LM.setKind(LengthModifier::AsSizeT);
747      return true;
748    } else if (Identifier->getName() == "ssize_t") {
749      // Not C99, but common in Unix.
750      LM.setKind(LengthModifier::AsSizeT);
751      return true;
752    } else if (Identifier->getName() == "intmax_t") {
753      LM.setKind(LengthModifier::AsIntMax);
754      return true;
755    } else if (Identifier->getName() == "uintmax_t") {
756      LM.setKind(LengthModifier::AsIntMax);
757      return true;
758    } else if (Identifier->getName() == "ptrdiff_t") {
759      LM.setKind(LengthModifier::AsPtrDiff);
760      return true;
761    }
762
763    QualType T = Typedef->getUnderlyingType();
764    if (!isa<TypedefType>(T))
765      break;
766
767    Typedef = cast<TypedefType>(T)->getDecl();
768  }
769  return false;
770}
771