1 // FormatString.cpp - Common stuff for handling printf/scanf formats -*- C++ -*-
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 // Shared details for processing format strings of printf and scanf
10 // (and friends).
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "FormatStringParsing.h"
15 #include "clang/Basic/LangOptions.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "llvm/Support/ConvertUTF.h"
18 #include <optional>
19 
20 using clang::analyze_format_string::ArgType;
21 using clang::analyze_format_string::FormatStringHandler;
22 using clang::analyze_format_string::FormatSpecifier;
23 using clang::analyze_format_string::LengthModifier;
24 using clang::analyze_format_string::OptionalAmount;
25 using clang::analyze_format_string::ConversionSpecifier;
26 using namespace clang;
27 
28 // Key function to FormatStringHandler.
29 FormatStringHandler::~FormatStringHandler() {}
30 
31 //===----------------------------------------------------------------------===//
32 // Functions for parsing format strings components in both printf and
33 // scanf format strings.
34 //===----------------------------------------------------------------------===//
35 
36 OptionalAmount
37 clang::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 
62 OptionalAmount
63 clang::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 
74 OptionalAmount
75 clang::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 
121 bool
122 clang::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 
143 bool
144 clang::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 
180 bool
181 clang::analyze_format_string::ParseVectorModifier(FormatStringHandler &H,
182                                                   FormatSpecifier &FS,
183                                                   const char *&I,
184                                                   const char *E,
185                                                   const LangOptions &LO) {
186   if (!LO.OpenCL)
187     return false;
188 
189   const char *Start = I;
190   if (*I == 'v') {
191     ++I;
192 
193     if (I == E) {
194       H.HandleIncompleteSpecifier(Start, E - Start);
195       return true;
196     }
197 
198     OptionalAmount NumElts = ParseAmount(I, E);
199     if (NumElts.getHowSpecified() != OptionalAmount::Constant) {
200       H.HandleIncompleteSpecifier(Start, E - Start);
201       return true;
202     }
203 
204     FS.setVectorNumElts(NumElts);
205   }
206 
207   return false;
208 }
209 
210 bool
211 clang::analyze_format_string::ParseLengthModifier(FormatSpecifier &FS,
212                                                   const char *&I,
213                                                   const char *E,
214                                                   const LangOptions &LO,
215                                                   bool IsScanf) {
216   LengthModifier::Kind lmKind = LengthModifier::None;
217   const char *lmPosition = I;
218   switch (*I) {
219     default:
220       return false;
221     case 'h':
222       ++I;
223       if (I != E && *I == 'h') {
224         ++I;
225         lmKind = LengthModifier::AsChar;
226       } else if (I != E && *I == 'l' && LO.OpenCL) {
227         ++I;
228         lmKind = LengthModifier::AsShortLong;
229       } else {
230         lmKind = LengthModifier::AsShort;
231       }
232       break;
233     case 'l':
234       ++I;
235       if (I != E && *I == 'l') {
236         ++I;
237         lmKind = LengthModifier::AsLongLong;
238       } else {
239         lmKind = LengthModifier::AsLong;
240       }
241       break;
242     case 'j': lmKind = LengthModifier::AsIntMax;     ++I; break;
243     case 'z': lmKind = LengthModifier::AsSizeT;      ++I; break;
244     case 't': lmKind = LengthModifier::AsPtrDiff;    ++I; break;
245     case 'L': lmKind = LengthModifier::AsLongDouble; ++I; break;
246     case 'q': lmKind = LengthModifier::AsQuad;       ++I; break;
247     case 'a':
248       if (IsScanf && !LO.C99 && !LO.CPlusPlus11) {
249         // For scanf in C90, look at the next character to see if this should
250         // be parsed as the GNU extension 'a' length modifier. If not, this
251         // will be parsed as a conversion specifier.
252         ++I;
253         if (I != E && (*I == 's' || *I == 'S' || *I == '[')) {
254           lmKind = LengthModifier::AsAllocate;
255           break;
256         }
257         --I;
258       }
259       return false;
260     case 'm':
261       if (IsScanf) {
262         lmKind = LengthModifier::AsMAllocate;
263         ++I;
264         break;
265       }
266       return false;
267     // printf: AsInt64, AsInt32, AsInt3264
268     // scanf:  AsInt64
269     case 'I':
270       if (I + 1 != E && I + 2 != E) {
271         if (I[1] == '6' && I[2] == '4') {
272           I += 3;
273           lmKind = LengthModifier::AsInt64;
274           break;
275         }
276         if (IsScanf)
277           return false;
278 
279         if (I[1] == '3' && I[2] == '2') {
280           I += 3;
281           lmKind = LengthModifier::AsInt32;
282           break;
283         }
284       }
285       ++I;
286       lmKind = LengthModifier::AsInt3264;
287       break;
288     case 'w':
289       lmKind = LengthModifier::AsWide; ++I; break;
290   }
291   LengthModifier lm(lmPosition, lmKind);
292   FS.setLengthModifier(lm);
293   return true;
294 }
295 
296 bool clang::analyze_format_string::ParseUTF8InvalidSpecifier(
297     const char *SpecifierBegin, const char *FmtStrEnd, unsigned &Len) {
298   if (SpecifierBegin + 1 >= FmtStrEnd)
299     return false;
300 
301   const llvm::UTF8 *SB =
302       reinterpret_cast<const llvm::UTF8 *>(SpecifierBegin + 1);
303   const llvm::UTF8 *SE = reinterpret_cast<const llvm::UTF8 *>(FmtStrEnd);
304   const char FirstByte = *SB;
305 
306   // If the invalid specifier is a multibyte UTF-8 string, return the
307   // total length accordingly so that the conversion specifier can be
308   // properly updated to reflect a complete UTF-8 specifier.
309   unsigned NumBytes = llvm::getNumBytesForUTF8(FirstByte);
310   if (NumBytes == 1)
311     return false;
312   if (SB + NumBytes > SE)
313     return false;
314 
315   Len = NumBytes + 1;
316   return true;
317 }
318 
319 //===----------------------------------------------------------------------===//
320 // Methods on ArgType.
321 //===----------------------------------------------------------------------===//
322 
323 clang::analyze_format_string::ArgType::MatchKind
324 ArgType::matchesType(ASTContext &C, QualType argTy) const {
325   // When using the format attribute in C++, you can receive a function or an
326   // array that will necessarily decay to a pointer when passed to the final
327   // format consumer. Apply decay before type comparison.
328   if (argTy->canDecayToPointerType())
329     argTy = C.getDecayedType(argTy);
330 
331   if (Ptr) {
332     // It has to be a pointer.
333     const PointerType *PT = argTy->getAs<PointerType>();
334     if (!PT)
335       return NoMatch;
336 
337     // We cannot write through a const qualified pointer.
338     if (PT->getPointeeType().isConstQualified())
339       return NoMatch;
340 
341     argTy = PT->getPointeeType();
342   }
343 
344   switch (K) {
345     case InvalidTy:
346       llvm_unreachable("ArgType must be valid");
347 
348     case UnknownTy:
349       return Match;
350 
351     case AnyCharTy: {
352       if (const auto *ETy = argTy->getAs<EnumType>()) {
353         // If the enum is incomplete we know nothing about the underlying type.
354         // Assume that it's 'int'.
355         if (!ETy->getDecl()->isComplete())
356           return NoMatch;
357         argTy = ETy->getDecl()->getIntegerType();
358       }
359 
360       if (const auto *BT = argTy->getAs<BuiltinType>()) {
361         // The types are perfectly matched?
362         switch (BT->getKind()) {
363         default:
364           break;
365         case BuiltinType::Char_S:
366         case BuiltinType::SChar:
367         case BuiltinType::UChar:
368         case BuiltinType::Char_U:
369         case BuiltinType::Bool:
370           return Match;
371         }
372         // "Partially matched" because of promotions?
373         if (!Ptr) {
374           switch (BT->getKind()) {
375           default:
376             break;
377           case BuiltinType::Int:
378           case BuiltinType::UInt:
379             return MatchPromotion;
380           case BuiltinType::Short:
381           case BuiltinType::UShort:
382           case BuiltinType::WChar_S:
383           case BuiltinType::WChar_U:
384             return NoMatchPromotionTypeConfusion;
385           }
386         }
387       }
388       return NoMatch;
389     }
390 
391     case SpecificTy: {
392       if (const EnumType *ETy = argTy->getAs<EnumType>()) {
393         // If the enum is incomplete we know nothing about the underlying type.
394         // Assume that it's 'int'.
395         if (!ETy->getDecl()->isComplete())
396           argTy = C.IntTy;
397         else
398           argTy = ETy->getDecl()->getIntegerType();
399       }
400       argTy = C.getCanonicalType(argTy).getUnqualifiedType();
401 
402       if (T == argTy)
403         return Match;
404       if (const auto *BT = argTy->getAs<BuiltinType>()) {
405         // Check if the only difference between them is signed vs unsigned
406         // if true, we consider they are compatible.
407         switch (BT->getKind()) {
408           default:
409             break;
410           case BuiltinType::Char_S:
411           case BuiltinType::SChar:
412           case BuiltinType::Char_U:
413           case BuiltinType::UChar:
414           case BuiltinType::Bool:
415             if (T == C.UnsignedShortTy || T == C.ShortTy)
416               return NoMatchTypeConfusion;
417             if (T == C.UnsignedCharTy || T == C.SignedCharTy)
418               return Match;
419             break;
420           case BuiltinType::Short:
421             if (T == C.UnsignedShortTy)
422               return Match;
423             break;
424           case BuiltinType::UShort:
425             if (T == C.ShortTy)
426               return Match;
427             break;
428           case BuiltinType::Int:
429             if (T == C.UnsignedIntTy)
430               return Match;
431             break;
432           case BuiltinType::UInt:
433             if (T == C.IntTy)
434               return Match;
435             break;
436           case BuiltinType::Long:
437             if (T == C.UnsignedLongTy)
438               return Match;
439             break;
440           case BuiltinType::ULong:
441             if (T == C.LongTy)
442               return Match;
443             break;
444           case BuiltinType::LongLong:
445             if (T == C.UnsignedLongLongTy)
446               return Match;
447             break;
448           case BuiltinType::ULongLong:
449             if (T == C.LongLongTy)
450               return Match;
451             break;
452           }
453           // "Partially matched" because of promotions?
454           if (!Ptr) {
455             switch (BT->getKind()) {
456             default:
457               break;
458             case BuiltinType::Int:
459             case BuiltinType::UInt:
460               if (T == C.SignedCharTy || T == C.UnsignedCharTy ||
461                   T == C.ShortTy || T == C.UnsignedShortTy || T == C.WCharTy ||
462                   T == C.WideCharTy)
463                 return MatchPromotion;
464               break;
465             case BuiltinType::Short:
466             case BuiltinType::UShort:
467               if (T == C.SignedCharTy || T == C.UnsignedCharTy)
468                 return NoMatchPromotionTypeConfusion;
469               break;
470             case BuiltinType::WChar_U:
471             case BuiltinType::WChar_S:
472               if (T != C.WCharTy && T != C.WideCharTy)
473                 return NoMatchPromotionTypeConfusion;
474             }
475           }
476       }
477       return NoMatch;
478     }
479 
480     case CStrTy: {
481       const PointerType *PT = argTy->getAs<PointerType>();
482       if (!PT)
483         return NoMatch;
484       QualType pointeeTy = PT->getPointeeType();
485       if (const BuiltinType *BT = pointeeTy->getAs<BuiltinType>())
486         switch (BT->getKind()) {
487           case BuiltinType::Char_U:
488           case BuiltinType::UChar:
489           case BuiltinType::Char_S:
490           case BuiltinType::SChar:
491             return Match;
492           default:
493             break;
494         }
495 
496       return NoMatch;
497     }
498 
499     case WCStrTy: {
500       const PointerType *PT = argTy->getAs<PointerType>();
501       if (!PT)
502         return NoMatch;
503       QualType pointeeTy =
504         C.getCanonicalType(PT->getPointeeType()).getUnqualifiedType();
505       return pointeeTy == C.getWideCharType() ? Match : NoMatch;
506     }
507 
508     case WIntTy: {
509       QualType WInt = C.getCanonicalType(C.getWIntType()).getUnqualifiedType();
510 
511       if (C.getCanonicalType(argTy).getUnqualifiedType() == WInt)
512         return Match;
513 
514       QualType PromoArg = C.isPromotableIntegerType(argTy)
515                               ? C.getPromotedIntegerType(argTy)
516                               : argTy;
517       PromoArg = C.getCanonicalType(PromoArg).getUnqualifiedType();
518 
519       // If the promoted argument is the corresponding signed type of the
520       // wint_t type, then it should match.
521       if (PromoArg->hasSignedIntegerRepresentation() &&
522           C.getCorrespondingUnsignedType(PromoArg) == WInt)
523         return Match;
524 
525       return WInt == PromoArg ? Match : NoMatch;
526     }
527 
528     case CPointerTy:
529       if (argTy->isVoidPointerType()) {
530         return Match;
531       } if (argTy->isPointerType() || argTy->isObjCObjectPointerType() ||
532             argTy->isBlockPointerType() || argTy->isNullPtrType()) {
533         return NoMatchPedantic;
534       } else {
535         return NoMatch;
536       }
537 
538     case ObjCPointerTy: {
539       if (argTy->getAs<ObjCObjectPointerType>() ||
540           argTy->getAs<BlockPointerType>())
541         return Match;
542 
543       // Handle implicit toll-free bridging.
544       if (const PointerType *PT = argTy->getAs<PointerType>()) {
545         // Things such as CFTypeRef are really just opaque pointers
546         // to C structs representing CF types that can often be bridged
547         // to Objective-C objects.  Since the compiler doesn't know which
548         // structs can be toll-free bridged, we just accept them all.
549         QualType pointee = PT->getPointeeType();
550         if (pointee->getAsStructureType() || pointee->isVoidType())
551           return Match;
552       }
553       return NoMatch;
554     }
555   }
556 
557   llvm_unreachable("Invalid ArgType Kind!");
558 }
559 
560 ArgType ArgType::makeVectorType(ASTContext &C, unsigned NumElts) const {
561   // Check for valid vector element types.
562   if (T.isNull())
563     return ArgType::Invalid();
564 
565   QualType Vec = C.getExtVectorType(T, NumElts);
566   return ArgType(Vec, Name);
567 }
568 
569 QualType ArgType::getRepresentativeType(ASTContext &C) const {
570   QualType Res;
571   switch (K) {
572     case InvalidTy:
573       llvm_unreachable("No representative type for Invalid ArgType");
574     case UnknownTy:
575       llvm_unreachable("No representative type for Unknown ArgType");
576     case AnyCharTy:
577       Res = C.CharTy;
578       break;
579     case SpecificTy:
580       Res = T;
581       break;
582     case CStrTy:
583       Res = C.getPointerType(C.CharTy);
584       break;
585     case WCStrTy:
586       Res = C.getPointerType(C.getWideCharType());
587       break;
588     case ObjCPointerTy:
589       Res = C.ObjCBuiltinIdTy;
590       break;
591     case CPointerTy:
592       Res = C.VoidPtrTy;
593       break;
594     case WIntTy: {
595       Res = C.getWIntType();
596       break;
597     }
598   }
599 
600   if (Ptr)
601     Res = C.getPointerType(Res);
602   return Res;
603 }
604 
605 std::string ArgType::getRepresentativeTypeName(ASTContext &C) const {
606   std::string S = getRepresentativeType(C).getAsString(C.getPrintingPolicy());
607 
608   std::string Alias;
609   if (Name) {
610     // Use a specific name for this type, e.g. "size_t".
611     Alias = Name;
612     if (Ptr) {
613       // If ArgType is actually a pointer to T, append an asterisk.
614       Alias += (Alias[Alias.size()-1] == '*') ? "*" : " *";
615     }
616     // If Alias is the same as the underlying type, e.g. wchar_t, then drop it.
617     if (S == Alias)
618       Alias.clear();
619   }
620 
621   if (!Alias.empty())
622     return std::string("'") + Alias + "' (aka '" + S + "')";
623   return std::string("'") + S + "'";
624 }
625 
626 
627 //===----------------------------------------------------------------------===//
628 // Methods on OptionalAmount.
629 //===----------------------------------------------------------------------===//
630 
631 ArgType
632 analyze_format_string::OptionalAmount::getArgType(ASTContext &Ctx) const {
633   return Ctx.IntTy;
634 }
635 
636 //===----------------------------------------------------------------------===//
637 // Methods on LengthModifier.
638 //===----------------------------------------------------------------------===//
639 
640 const char *
641 analyze_format_string::LengthModifier::toString() const {
642   switch (kind) {
643   case AsChar:
644     return "hh";
645   case AsShort:
646     return "h";
647   case AsShortLong:
648     return "hl";
649   case AsLong: // or AsWideChar
650     return "l";
651   case AsLongLong:
652     return "ll";
653   case AsQuad:
654     return "q";
655   case AsIntMax:
656     return "j";
657   case AsSizeT:
658     return "z";
659   case AsPtrDiff:
660     return "t";
661   case AsInt32:
662     return "I32";
663   case AsInt3264:
664     return "I";
665   case AsInt64:
666     return "I64";
667   case AsLongDouble:
668     return "L";
669   case AsAllocate:
670     return "a";
671   case AsMAllocate:
672     return "m";
673   case AsWide:
674     return "w";
675   case None:
676     return "";
677   }
678   return nullptr;
679 }
680 
681 //===----------------------------------------------------------------------===//
682 // Methods on ConversionSpecifier.
683 //===----------------------------------------------------------------------===//
684 
685 const char *ConversionSpecifier::toString() const {
686   switch (kind) {
687   case bArg: return "b";
688   case BArg: return "B";
689   case dArg: return "d";
690   case DArg: return "D";
691   case iArg: return "i";
692   case oArg: return "o";
693   case OArg: return "O";
694   case uArg: return "u";
695   case UArg: return "U";
696   case xArg: return "x";
697   case XArg: return "X";
698   case fArg: return "f";
699   case FArg: return "F";
700   case eArg: return "e";
701   case EArg: return "E";
702   case gArg: return "g";
703   case GArg: return "G";
704   case aArg: return "a";
705   case AArg: return "A";
706   case cArg: return "c";
707   case sArg: return "s";
708   case pArg: return "p";
709   case PArg:
710     return "P";
711   case nArg: return "n";
712   case PercentArg:  return "%";
713   case ScanListArg: return "[";
714   case InvalidSpecifier: return nullptr;
715 
716   // POSIX unicode extensions.
717   case CArg: return "C";
718   case SArg: return "S";
719 
720   // Objective-C specific specifiers.
721   case ObjCObjArg: return "@";
722 
723   // FreeBSD kernel specific specifiers.
724   case FreeBSDbArg: return "b";
725   case FreeBSDDArg: return "D";
726   case FreeBSDrArg: return "r";
727   case FreeBSDyArg: return "y";
728 
729   // GlibC specific specifiers.
730   case PrintErrno: return "m";
731 
732   // MS specific specifiers.
733   case ZArg: return "Z";
734   }
735   return nullptr;
736 }
737 
738 std::optional<ConversionSpecifier>
739 ConversionSpecifier::getStandardSpecifier() const {
740   ConversionSpecifier::Kind NewKind;
741 
742   switch (getKind()) {
743   default:
744     return std::nullopt;
745   case DArg:
746     NewKind = dArg;
747     break;
748   case UArg:
749     NewKind = uArg;
750     break;
751   case OArg:
752     NewKind = oArg;
753     break;
754   }
755 
756   ConversionSpecifier FixedCS(*this);
757   FixedCS.setKind(NewKind);
758   return FixedCS;
759 }
760 
761 //===----------------------------------------------------------------------===//
762 // Methods on OptionalAmount.
763 //===----------------------------------------------------------------------===//
764 
765 void OptionalAmount::toString(raw_ostream &os) const {
766   switch (hs) {
767   case Invalid:
768   case NotSpecified:
769     return;
770   case Arg:
771     if (UsesDotPrefix)
772         os << ".";
773     if (usesPositionalArg())
774       os << "*" << getPositionalArgIndex() << "$";
775     else
776       os << "*";
777     break;
778   case Constant:
779     if (UsesDotPrefix)
780         os << ".";
781     os << amt;
782     break;
783   }
784 }
785 
786 bool FormatSpecifier::hasValidLengthModifier(const TargetInfo &Target,
787                                              const LangOptions &LO) const {
788   switch (LM.getKind()) {
789     case LengthModifier::None:
790       return true;
791 
792     // Handle most integer flags
793     case LengthModifier::AsShort:
794       // Length modifier only applies to FP vectors.
795       if (LO.OpenCL && CS.isDoubleArg())
796         return !VectorNumElts.isInvalid();
797 
798       if (Target.getTriple().isOSMSVCRT()) {
799         switch (CS.getKind()) {
800           case ConversionSpecifier::cArg:
801           case ConversionSpecifier::CArg:
802           case ConversionSpecifier::sArg:
803           case ConversionSpecifier::SArg:
804           case ConversionSpecifier::ZArg:
805             return true;
806           default:
807             break;
808         }
809       }
810       [[fallthrough]];
811     case LengthModifier::AsChar:
812     case LengthModifier::AsLongLong:
813     case LengthModifier::AsQuad:
814     case LengthModifier::AsIntMax:
815     case LengthModifier::AsSizeT:
816     case LengthModifier::AsPtrDiff:
817       switch (CS.getKind()) {
818         case ConversionSpecifier::bArg:
819         case ConversionSpecifier::BArg:
820         case ConversionSpecifier::dArg:
821         case ConversionSpecifier::DArg:
822         case ConversionSpecifier::iArg:
823         case ConversionSpecifier::oArg:
824         case ConversionSpecifier::OArg:
825         case ConversionSpecifier::uArg:
826         case ConversionSpecifier::UArg:
827         case ConversionSpecifier::xArg:
828         case ConversionSpecifier::XArg:
829         case ConversionSpecifier::nArg:
830           return true;
831         case ConversionSpecifier::FreeBSDrArg:
832         case ConversionSpecifier::FreeBSDyArg:
833           return Target.getTriple().isOSFreeBSD() || Target.getTriple().isPS();
834         default:
835           return false;
836       }
837 
838     case LengthModifier::AsShortLong:
839       return LO.OpenCL && !VectorNumElts.isInvalid();
840 
841     // Handle 'l' flag
842     case LengthModifier::AsLong: // or AsWideChar
843       if (CS.isDoubleArg()) {
844         // Invalid for OpenCL FP scalars.
845         if (LO.OpenCL && VectorNumElts.isInvalid())
846           return false;
847         return true;
848       }
849 
850       switch (CS.getKind()) {
851         case ConversionSpecifier::dArg:
852         case ConversionSpecifier::DArg:
853         case ConversionSpecifier::iArg:
854         case ConversionSpecifier::oArg:
855         case ConversionSpecifier::OArg:
856         case ConversionSpecifier::uArg:
857         case ConversionSpecifier::UArg:
858         case ConversionSpecifier::xArg:
859         case ConversionSpecifier::XArg:
860         case ConversionSpecifier::nArg:
861         case ConversionSpecifier::cArg:
862         case ConversionSpecifier::sArg:
863         case ConversionSpecifier::ScanListArg:
864         case ConversionSpecifier::ZArg:
865           return true;
866         case ConversionSpecifier::FreeBSDrArg:
867         case ConversionSpecifier::FreeBSDyArg:
868           return Target.getTriple().isOSFreeBSD() || Target.getTriple().isPS();
869         default:
870           return false;
871       }
872 
873     case LengthModifier::AsLongDouble:
874       switch (CS.getKind()) {
875         case ConversionSpecifier::aArg:
876         case ConversionSpecifier::AArg:
877         case ConversionSpecifier::fArg:
878         case ConversionSpecifier::FArg:
879         case ConversionSpecifier::eArg:
880         case ConversionSpecifier::EArg:
881         case ConversionSpecifier::gArg:
882         case ConversionSpecifier::GArg:
883           return true;
884         // GNU libc extension.
885         case ConversionSpecifier::dArg:
886         case ConversionSpecifier::iArg:
887         case ConversionSpecifier::oArg:
888         case ConversionSpecifier::uArg:
889         case ConversionSpecifier::xArg:
890         case ConversionSpecifier::XArg:
891           return !Target.getTriple().isOSDarwin() &&
892                  !Target.getTriple().isOSWindows();
893         default:
894           return false;
895       }
896 
897     case LengthModifier::AsAllocate:
898       switch (CS.getKind()) {
899         case ConversionSpecifier::sArg:
900         case ConversionSpecifier::SArg:
901         case ConversionSpecifier::ScanListArg:
902           return true;
903         default:
904           return false;
905       }
906 
907     case LengthModifier::AsMAllocate:
908       switch (CS.getKind()) {
909         case ConversionSpecifier::cArg:
910         case ConversionSpecifier::CArg:
911         case ConversionSpecifier::sArg:
912         case ConversionSpecifier::SArg:
913         case ConversionSpecifier::ScanListArg:
914           return true;
915         default:
916           return false;
917       }
918     case LengthModifier::AsInt32:
919     case LengthModifier::AsInt3264:
920     case LengthModifier::AsInt64:
921       switch (CS.getKind()) {
922         case ConversionSpecifier::dArg:
923         case ConversionSpecifier::iArg:
924         case ConversionSpecifier::oArg:
925         case ConversionSpecifier::uArg:
926         case ConversionSpecifier::xArg:
927         case ConversionSpecifier::XArg:
928           return Target.getTriple().isOSMSVCRT();
929         default:
930           return false;
931       }
932     case LengthModifier::AsWide:
933       switch (CS.getKind()) {
934         case ConversionSpecifier::cArg:
935         case ConversionSpecifier::CArg:
936         case ConversionSpecifier::sArg:
937         case ConversionSpecifier::SArg:
938         case ConversionSpecifier::ZArg:
939           return Target.getTriple().isOSMSVCRT();
940         default:
941           return false;
942       }
943   }
944   llvm_unreachable("Invalid LengthModifier Kind!");
945 }
946 
947 bool FormatSpecifier::hasStandardLengthModifier() const {
948   switch (LM.getKind()) {
949     case LengthModifier::None:
950     case LengthModifier::AsChar:
951     case LengthModifier::AsShort:
952     case LengthModifier::AsLong:
953     case LengthModifier::AsLongLong:
954     case LengthModifier::AsIntMax:
955     case LengthModifier::AsSizeT:
956     case LengthModifier::AsPtrDiff:
957     case LengthModifier::AsLongDouble:
958       return true;
959     case LengthModifier::AsAllocate:
960     case LengthModifier::AsMAllocate:
961     case LengthModifier::AsQuad:
962     case LengthModifier::AsInt32:
963     case LengthModifier::AsInt3264:
964     case LengthModifier::AsInt64:
965     case LengthModifier::AsWide:
966     case LengthModifier::AsShortLong: // ???
967       return false;
968   }
969   llvm_unreachable("Invalid LengthModifier Kind!");
970 }
971 
972 bool FormatSpecifier::hasStandardConversionSpecifier(
973     const LangOptions &LangOpt) const {
974   switch (CS.getKind()) {
975     case ConversionSpecifier::bArg:
976     case ConversionSpecifier::BArg:
977     case ConversionSpecifier::cArg:
978     case ConversionSpecifier::dArg:
979     case ConversionSpecifier::iArg:
980     case ConversionSpecifier::oArg:
981     case ConversionSpecifier::uArg:
982     case ConversionSpecifier::xArg:
983     case ConversionSpecifier::XArg:
984     case ConversionSpecifier::fArg:
985     case ConversionSpecifier::FArg:
986     case ConversionSpecifier::eArg:
987     case ConversionSpecifier::EArg:
988     case ConversionSpecifier::gArg:
989     case ConversionSpecifier::GArg:
990     case ConversionSpecifier::aArg:
991     case ConversionSpecifier::AArg:
992     case ConversionSpecifier::sArg:
993     case ConversionSpecifier::pArg:
994     case ConversionSpecifier::nArg:
995     case ConversionSpecifier::ObjCObjArg:
996     case ConversionSpecifier::ScanListArg:
997     case ConversionSpecifier::PercentArg:
998     case ConversionSpecifier::PArg:
999       return true;
1000     case ConversionSpecifier::CArg:
1001     case ConversionSpecifier::SArg:
1002       return LangOpt.ObjC;
1003     case ConversionSpecifier::InvalidSpecifier:
1004     case ConversionSpecifier::FreeBSDbArg:
1005     case ConversionSpecifier::FreeBSDDArg:
1006     case ConversionSpecifier::FreeBSDrArg:
1007     case ConversionSpecifier::FreeBSDyArg:
1008     case ConversionSpecifier::PrintErrno:
1009     case ConversionSpecifier::DArg:
1010     case ConversionSpecifier::OArg:
1011     case ConversionSpecifier::UArg:
1012     case ConversionSpecifier::ZArg:
1013       return false;
1014   }
1015   llvm_unreachable("Invalid ConversionSpecifier Kind!");
1016 }
1017 
1018 bool FormatSpecifier::hasStandardLengthConversionCombination() const {
1019   if (LM.getKind() == LengthModifier::AsLongDouble) {
1020     switch(CS.getKind()) {
1021         case ConversionSpecifier::dArg:
1022         case ConversionSpecifier::iArg:
1023         case ConversionSpecifier::oArg:
1024         case ConversionSpecifier::uArg:
1025         case ConversionSpecifier::xArg:
1026         case ConversionSpecifier::XArg:
1027           return false;
1028         default:
1029           return true;
1030     }
1031   }
1032   return true;
1033 }
1034 
1035 std::optional<LengthModifier>
1036 FormatSpecifier::getCorrectedLengthModifier() const {
1037   if (CS.isAnyIntArg() || CS.getKind() == ConversionSpecifier::nArg) {
1038     if (LM.getKind() == LengthModifier::AsLongDouble ||
1039         LM.getKind() == LengthModifier::AsQuad) {
1040       LengthModifier FixedLM(LM);
1041       FixedLM.setKind(LengthModifier::AsLongLong);
1042       return FixedLM;
1043     }
1044   }
1045 
1046   return std::nullopt;
1047 }
1048 
1049 bool FormatSpecifier::namedTypeToLengthModifier(QualType QT,
1050                                                 LengthModifier &LM) {
1051   for (/**/; const auto *TT = QT->getAs<TypedefType>();
1052        QT = TT->getDecl()->getUnderlyingType()) {
1053     const TypedefNameDecl *Typedef = TT->getDecl();
1054     const IdentifierInfo *Identifier = Typedef->getIdentifier();
1055     if (Identifier->getName() == "size_t") {
1056       LM.setKind(LengthModifier::AsSizeT);
1057       return true;
1058     } else if (Identifier->getName() == "ssize_t") {
1059       // Not C99, but common in Unix.
1060       LM.setKind(LengthModifier::AsSizeT);
1061       return true;
1062     } else if (Identifier->getName() == "intmax_t") {
1063       LM.setKind(LengthModifier::AsIntMax);
1064       return true;
1065     } else if (Identifier->getName() == "uintmax_t") {
1066       LM.setKind(LengthModifier::AsIntMax);
1067       return true;
1068     } else if (Identifier->getName() == "ptrdiff_t") {
1069       LM.setKind(LengthModifier::AsPtrDiff);
1070       return true;
1071     }
1072   }
1073   return false;
1074 }
1075