PrintfFormatString.cpp revision 16b6f68e2012abb1b36c44dd9412e09e09488e20 
1//== PrintfFormatString.cpp - Analysis of printf format strings --*- 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// Handling of format string in printf and friends.  The structure of format
11// strings for fprintf() are described in C99 7.19.6.1.
12//
13//===----------------------------------------------------------------------===//
14
15#include "clang/Analysis/Analyses/FormatString.h"
16#include "FormatStringParsing.h"
17
18using clang::analyze_format_string::ArgTypeResult;
19using clang::analyze_format_string::FormatStringHandler;
20using clang::analyze_format_string::LengthModifier;
21using clang::analyze_format_string::OptionalAmount;
22using clang::analyze_format_string::ConversionSpecifier;
23using clang::analyze_printf::PrintfSpecifier;
24
25using namespace clang;
26
27typedef clang::analyze_format_string::SpecifierResult<PrintfSpecifier>
28        PrintfSpecifierResult;
29
30//===----------------------------------------------------------------------===//
31// Methods for parsing format strings.
32//===----------------------------------------------------------------------===//
33
34using analyze_format_string::ParseNonPositionAmount;
35
36static bool ParsePrecision(FormatStringHandler &H, PrintfSpecifier &FS,
37                           const char *Start, const char *&Beg, const char *E,
38                           unsigned *argIndex) {
39  if (argIndex) {
40    FS.setPrecision(ParseNonPositionAmount(Beg, E, *argIndex));
41  }
42  else {
43    const OptionalAmount Amt = ParsePositionAmount(H, Start, Beg, E,
44                                           analyze_format_string::PrecisionPos);
45    if (Amt.isInvalid())
46      return true;
47    FS.setPrecision(Amt);
48  }
49  return false;
50}
51
52static PrintfSpecifierResult ParsePrintfSpecifier(FormatStringHandler &H,
53                                                  const char *&Beg,
54                                                  const char *E,
55                                                  unsigned &argIndex) {
56
57  using namespace clang::analyze_format_string;
58  using namespace clang::analyze_printf;
59
60  const char *I = Beg;
61  const char *Start = 0;
62  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
63
64  // Look for a '%' character that indicates the start of a format specifier.
65  for ( ; I != E ; ++I) {
66    char c = *I;
67    if (c == '\0') {
68      // Detect spurious null characters, which are likely errors.
69      H.HandleNullChar(I);
70      return true;
71    }
72    if (c == '%') {
73      Start = I++;  // Record the start of the format specifier.
74      break;
75    }
76  }
77
78  // No format specifier found?
79  if (!Start)
80    return false;
81
82  if (I == E) {
83    // No more characters left?
84    H.HandleIncompleteSpecifier(Start, E - Start);
85    return true;
86  }
87
88  PrintfSpecifier FS;
89  if (ParseArgPosition(H, FS, Start, I, E))
90    return true;
91
92  if (I == E) {
93    // No more characters left?
94    H.HandleIncompleteSpecifier(Start, E - Start);
95    return true;
96  }
97
98  // Look for flags (if any).
99  bool hasMore = true;
100  for ( ; I != E; ++I) {
101    switch (*I) {
102      default: hasMore = false; break;
103      case '-': FS.setIsLeftJustified(I); break;
104      case '+': FS.setHasPlusPrefix(I); break;
105      case ' ': FS.setHasSpacePrefix(I); break;
106      case '#': FS.setHasAlternativeForm(I); break;
107      case '0': FS.setHasLeadingZeros(I); break;
108    }
109    if (!hasMore)
110      break;
111  }
112
113  if (I == E) {
114    // No more characters left?
115    H.HandleIncompleteSpecifier(Start, E - Start);
116    return true;
117  }
118
119  // Look for the field width (if any).
120  if (ParseFieldWidth(H, FS, Start, I, E,
121                      FS.usesPositionalArg() ? 0 : &argIndex))
122    return true;
123
124  if (I == E) {
125    // No more characters left?
126    H.HandleIncompleteSpecifier(Start, E - Start);
127    return true;
128  }
129
130  // Look for the precision (if any).
131  if (*I == '.') {
132    ++I;
133    if (I == E) {
134      H.HandleIncompleteSpecifier(Start, E - Start);
135      return true;
136    }
137
138    if (ParsePrecision(H, FS, Start, I, E,
139                       FS.usesPositionalArg() ? 0 : &argIndex))
140      return true;
141
142    if (I == E) {
143      // No more characters left?
144      H.HandleIncompleteSpecifier(Start, E - Start);
145      return true;
146    }
147  }
148
149  // Look for the length modifier.
150  if (ParseLengthModifier(FS, I, E) && I == E) {
151    // No more characters left?
152    H.HandleIncompleteSpecifier(Start, E - Start);
153    return true;
154  }
155
156  if (*I == '\0') {
157    // Detect spurious null characters, which are likely errors.
158    H.HandleNullChar(I);
159    return true;
160  }
161
162  // Finally, look for the conversion specifier.
163  const char *conversionPosition = I++;
164  ConversionSpecifier::Kind k = ConversionSpecifier::InvalidSpecifier;
165  switch (*conversionPosition) {
166    default:
167      break;
168    // C99: 7.19.6.1 (section 8).
169    case '%': k = ConversionSpecifier::PercentArg;   break;
170    case 'A': k = ConversionSpecifier::AArg; break;
171    case 'E': k = ConversionSpecifier::EArg; break;
172    case 'F': k = ConversionSpecifier::FArg; break;
173    case 'G': k = ConversionSpecifier::GArg; break;
174    case 'X': k = ConversionSpecifier::XArg; break;
175    case 'a': k = ConversionSpecifier::aArg; break;
176    case 'c': k = ConversionSpecifier::cArg; break;
177    case 'd': k = ConversionSpecifier::dArg; break;
178    case 'e': k = ConversionSpecifier::eArg; break;
179    case 'f': k = ConversionSpecifier::fArg; break;
180    case 'g': k = ConversionSpecifier::gArg; break;
181    case 'i': k = ConversionSpecifier::iArg; break;
182    case 'n': k = ConversionSpecifier::nArg; break;
183    case 'o': k = ConversionSpecifier::oArg; break;
184    case 'p': k = ConversionSpecifier::pArg;   break;
185    case 's': k = ConversionSpecifier::sArg;      break;
186    case 'u': k = ConversionSpecifier::uArg; break;
187    case 'x': k = ConversionSpecifier::xArg; break;
188    // Mac OS X (unicode) specific
189    case 'C': k = ConversionSpecifier::CArg; break;
190    case 'S': k = ConversionSpecifier::SArg; break;
191    // Objective-C.
192    case '@': k = ConversionSpecifier::ObjCObjArg; break;
193    // Glibc specific.
194    case 'm': k = ConversionSpecifier::PrintErrno; break;
195  }
196  PrintfConversionSpecifier CS(conversionPosition, k);
197  FS.setConversionSpecifier(CS);
198  if (CS.consumesDataArgument() && !FS.usesPositionalArg())
199    FS.setArgIndex(argIndex++);
200
201  if (k == ConversionSpecifier::InvalidSpecifier) {
202    // Assume the conversion takes one argument.
203    return !H.HandleInvalidPrintfConversionSpecifier(FS, Beg, I - Beg);
204  }
205  return PrintfSpecifierResult(Start, FS);
206}
207
208bool clang::analyze_format_string::ParsePrintfString(FormatStringHandler &H,
209                                                     const char *I,
210                                                     const char *E) {
211
212  unsigned argIndex = 0;
213
214  // Keep looking for a format specifier until we have exhausted the string.
215  while (I != E) {
216    const PrintfSpecifierResult &FSR = ParsePrintfSpecifier(H, I, E, argIndex);
217    // Did a fail-stop error of any kind occur when parsing the specifier?
218    // If so, don't do any more processing.
219    if (FSR.shouldStop())
220      return true;;
221    // Did we exhaust the string or encounter an error that
222    // we can recover from?
223    if (!FSR.hasValue())
224      continue;
225    // We have a format specifier.  Pass it to the callback.
226    if (!H.HandlePrintfSpecifier(FSR.getValue(), FSR.getStart(),
227                                 I - FSR.getStart()))
228      return true;
229  }
230  assert(I == E && "Format string not exhausted");
231  return false;
232}
233
234//===----------------------------------------------------------------------===//
235// Methods on ConversionSpecifier.
236//===----------------------------------------------------------------------===//
237const char *ConversionSpecifier::toString() const {
238  switch (kind) {
239  case dArg: return "d";
240  case iArg: return "i";
241  case oArg: return "o";
242  case uArg: return "u";
243  case xArg: return "x";
244  case XArg: return "X";
245  case fArg: return "f";
246  case FArg: return "F";
247  case eArg: return "e";
248  case EArg: return "E";
249  case gArg: return "g";
250  case GArg: return "G";
251  case aArg: return "a";
252  case AArg: return "A";
253  case cArg: return "c";
254  case sArg: return "s";
255  case pArg: return "p";
256  case nArg: return "n";
257  case PercentArg:  return "%";
258  case ScanListArg: return "[";
259  case InvalidSpecifier: return NULL;
260
261  // MacOS X unicode extensions.
262  case CArg: return "C";
263  case SArg: return "S";
264
265  // Objective-C specific specifiers.
266  case ObjCObjArg: return "@";
267
268  // GlibC specific specifiers.
269  case PrintErrno: return "m";
270  }
271  return NULL;
272}
273
274//===----------------------------------------------------------------------===//
275// Methods on PrintfSpecifier.
276//===----------------------------------------------------------------------===//
277
278ArgTypeResult PrintfSpecifier::getArgType(ASTContext &Ctx) const {
279  const PrintfConversionSpecifier &CS = getConversionSpecifier();
280
281  if (!CS.consumesDataArgument())
282    return ArgTypeResult::Invalid();
283
284  if (CS.getKind() == ConversionSpecifier::cArg)
285    switch (LM.getKind()) {
286      case LengthModifier::None: return Ctx.IntTy;
287      case LengthModifier::AsLong: return ArgTypeResult::WIntTy;
288      default:
289        return ArgTypeResult::Invalid();
290    }
291
292  if (CS.isIntArg())
293    switch (LM.getKind()) {
294      case LengthModifier::AsLongDouble:
295        return ArgTypeResult::Invalid();
296      case LengthModifier::None: return Ctx.IntTy;
297      case LengthModifier::AsChar: return Ctx.SignedCharTy;
298      case LengthModifier::AsShort: return Ctx.ShortTy;
299      case LengthModifier::AsLong: return Ctx.LongTy;
300      case LengthModifier::AsLongLong: return Ctx.LongLongTy;
301      case LengthModifier::AsIntMax:
302        // FIXME: Return unknown for now.
303        return ArgTypeResult();
304      case LengthModifier::AsSizeT: return Ctx.getSizeType();
305      case LengthModifier::AsPtrDiff: return Ctx.getPointerDiffType();
306    }
307
308  if (CS.isUIntArg())
309    switch (LM.getKind()) {
310      case LengthModifier::AsLongDouble:
311        return ArgTypeResult::Invalid();
312      case LengthModifier::None: return Ctx.UnsignedIntTy;
313      case LengthModifier::AsChar: return Ctx.UnsignedCharTy;
314      case LengthModifier::AsShort: return Ctx.UnsignedShortTy;
315      case LengthModifier::AsLong: return Ctx.UnsignedLongTy;
316      case LengthModifier::AsLongLong: return Ctx.UnsignedLongLongTy;
317      case LengthModifier::AsIntMax:
318        // FIXME: Return unknown for now.
319        return ArgTypeResult();
320      case LengthModifier::AsSizeT:
321        // FIXME: How to get the corresponding unsigned
322        // version of size_t?
323        return ArgTypeResult();
324      case LengthModifier::AsPtrDiff:
325        // FIXME: How to get the corresponding unsigned
326        // version of ptrdiff_t?
327        return ArgTypeResult();
328    }
329
330  if (CS.isDoubleArg()) {
331    if (LM.getKind() == LengthModifier::AsLongDouble)
332      return Ctx.LongDoubleTy;
333    return Ctx.DoubleTy;
334  }
335
336  switch (CS.getKind()) {
337    case ConversionSpecifier::sArg:
338      return ArgTypeResult(LM.getKind() == LengthModifier::AsWideChar ?
339          ArgTypeResult::WCStrTy : ArgTypeResult::CStrTy);
340    case ConversionSpecifier::SArg:
341      // FIXME: This appears to be Mac OS X specific.
342      return ArgTypeResult::WCStrTy;
343    case ConversionSpecifier::CArg:
344      return Ctx.WCharTy;
345    case ConversionSpecifier::pArg:
346      return ArgTypeResult::CPointerTy;
347    default:
348      break;
349  }
350
351  // FIXME: Handle other cases.
352  return ArgTypeResult();
353}
354
355bool PrintfSpecifier::fixType(QualType QT) {
356  // Handle strings first (char *, wchar_t *)
357  if (QT->isPointerType() && (QT->getPointeeType()->isAnyCharacterType())) {
358    CS.setKind(ConversionSpecifier::sArg);
359
360    // Disable irrelevant flags
361    HasAlternativeForm = 0;
362    HasLeadingZeroes = 0;
363
364    // Set the long length modifier for wide characters
365    if (QT->getPointeeType()->isWideCharType())
366      LM.setKind(LengthModifier::AsWideChar);
367
368    return true;
369  }
370
371  // We can only work with builtin types.
372  if (!QT->isBuiltinType())
373    return false;
374
375  // Everything else should be a base type
376  const BuiltinType *BT = QT->getAs<BuiltinType>();
377
378  // Set length modifier
379  switch (BT->getKind()) {
380  default:
381    // The rest of the conversions are either optional or for non-builtin types
382    LM.setKind(LengthModifier::None);
383    break;
384
385  case BuiltinType::Char_U:
386  case BuiltinType::UChar:
387  case BuiltinType::Char_S:
388  case BuiltinType::SChar:
389    LM.setKind(LengthModifier::AsChar);
390    break;
391
392  case BuiltinType::Short:
393  case BuiltinType::UShort:
394    LM.setKind(LengthModifier::AsShort);
395    break;
396
397  case BuiltinType::WChar:
398  case BuiltinType::Long:
399  case BuiltinType::ULong:
400    LM.setKind(LengthModifier::AsLong);
401    break;
402
403  case BuiltinType::LongLong:
404  case BuiltinType::ULongLong:
405    LM.setKind(LengthModifier::AsLongLong);
406    break;
407
408  case BuiltinType::LongDouble:
409    LM.setKind(LengthModifier::AsLongDouble);
410    break;
411  }
412
413  // Set conversion specifier and disable any flags which do not apply to it.
414  // Let typedefs to char fall through to int, as %c is silly for uint8_t.
415  if (isa<TypedefType>(QT) && QT->isAnyCharacterType()) {
416    CS.setKind(ConversionSpecifier::cArg);
417    LM.setKind(LengthModifier::None);
418    Precision.setHowSpecified(OptionalAmount::NotSpecified);
419    HasAlternativeForm = 0;
420    HasLeadingZeroes = 0;
421    HasPlusPrefix = 0;
422  }
423  // Test for Floating type first as LongDouble can pass isUnsignedIntegerType
424  else if (QT->isRealFloatingType()) {
425    CS.setKind(ConversionSpecifier::fArg);
426  }
427  else if (QT->isPointerType()) {
428    CS.setKind(ConversionSpecifier::pArg);
429    Precision.setHowSpecified(OptionalAmount::NotSpecified);
430    HasAlternativeForm = 0;
431    HasLeadingZeroes = 0;
432    HasPlusPrefix = 0;
433  }
434  else if (QT->isSignedIntegerType()) {
435    CS.setKind(ConversionSpecifier::dArg);
436    HasAlternativeForm = 0;
437  }
438  else if (QT->isUnsignedIntegerType()) {
439    CS.setKind(ConversionSpecifier::uArg);
440    HasAlternativeForm = 0;
441    HasPlusPrefix = 0;
442  }
443  else {
444    return false;
445  }
446
447  return true;
448}
449
450void PrintfSpecifier::toString(llvm::raw_ostream &os) const {
451  // Whilst some features have no defined order, we are using the order
452  // appearing in the C99 standard (ISO/IEC 9899:1999 (E) ¤7.19.6.1)
453  os << "%";
454
455  // Positional args
456  if (usesPositionalArg()) {
457    os << getPositionalArgIndex() << "$";
458  }
459
460  // Conversion flags
461  if (IsLeftJustified)    os << "-";
462  if (HasPlusPrefix)      os << "+";
463  if (HasSpacePrefix)     os << " ";
464  if (HasAlternativeForm) os << "#";
465  if (HasLeadingZeroes)   os << "0";
466
467  // Minimum field width
468  FieldWidth.toString(os);
469  // Precision
470  Precision.toString(os);
471  // Length modifier
472  os << LM.toString();
473  // Conversion specifier
474  os << CS.toString();
475}
476
477bool PrintfSpecifier::hasValidPlusPrefix() const {
478  if (!HasPlusPrefix)
479    return true;
480
481  // The plus prefix only makes sense for signed conversions
482  switch (CS.getKind()) {
483  case ConversionSpecifier::dArg:
484  case ConversionSpecifier::iArg:
485  case ConversionSpecifier::fArg:
486  case ConversionSpecifier::FArg:
487  case ConversionSpecifier::eArg:
488  case ConversionSpecifier::EArg:
489  case ConversionSpecifier::gArg:
490  case ConversionSpecifier::GArg:
491  case ConversionSpecifier::aArg:
492  case ConversionSpecifier::AArg:
493    return true;
494
495  default:
496    return false;
497  }
498}
499
500bool PrintfSpecifier::hasValidAlternativeForm() const {
501  if (!HasAlternativeForm)
502    return true;
503
504  // Alternate form flag only valid with the oxaAeEfFgG conversions
505  switch (CS.getKind()) {
506  case ConversionSpecifier::oArg:
507  case ConversionSpecifier::xArg:
508  case ConversionSpecifier::aArg:
509  case ConversionSpecifier::AArg:
510  case ConversionSpecifier::eArg:
511  case ConversionSpecifier::EArg:
512  case ConversionSpecifier::fArg:
513  case ConversionSpecifier::FArg:
514  case ConversionSpecifier::gArg:
515  case ConversionSpecifier::GArg:
516    return true;
517
518  default:
519    return false;
520  }
521}
522
523bool PrintfSpecifier::hasValidLeadingZeros() const {
524  if (!HasLeadingZeroes)
525    return true;
526
527  // Leading zeroes flag only valid with the diouxXaAeEfFgG conversions
528  switch (CS.getKind()) {
529  case ConversionSpecifier::dArg:
530  case ConversionSpecifier::iArg:
531  case ConversionSpecifier::oArg:
532  case ConversionSpecifier::uArg:
533  case ConversionSpecifier::xArg:
534  case ConversionSpecifier::XArg:
535  case ConversionSpecifier::aArg:
536  case ConversionSpecifier::AArg:
537  case ConversionSpecifier::eArg:
538  case ConversionSpecifier::EArg:
539  case ConversionSpecifier::fArg:
540  case ConversionSpecifier::FArg:
541  case ConversionSpecifier::gArg:
542  case ConversionSpecifier::GArg:
543    return true;
544
545  default:
546    return false;
547  }
548}
549
550bool PrintfSpecifier::hasValidSpacePrefix() const {
551  if (!HasSpacePrefix)
552    return true;
553
554  // The space prefix only makes sense for signed conversions
555  switch (CS.getKind()) {
556  case ConversionSpecifier::dArg:
557  case ConversionSpecifier::iArg:
558  case ConversionSpecifier::fArg:
559  case ConversionSpecifier::FArg:
560  case ConversionSpecifier::eArg:
561  case ConversionSpecifier::EArg:
562  case ConversionSpecifier::gArg:
563  case ConversionSpecifier::GArg:
564  case ConversionSpecifier::aArg:
565  case ConversionSpecifier::AArg:
566    return true;
567
568  default:
569    return false;
570  }
571}
572
573bool PrintfSpecifier::hasValidLeftJustified() const {
574  if (!IsLeftJustified)
575    return true;
576
577  // The left justified flag is valid for all conversions except n
578  switch (CS.getKind()) {
579  case ConversionSpecifier::nArg:
580    return false;
581
582  default:
583    return true;
584  }
585}
586
587bool PrintfSpecifier::hasValidPrecision() const {
588  if (Precision.getHowSpecified() == OptionalAmount::NotSpecified)
589    return true;
590
591  // Precision is only valid with the diouxXaAeEfFgGs conversions
592  switch (CS.getKind()) {
593  case ConversionSpecifier::dArg:
594  case ConversionSpecifier::iArg:
595  case ConversionSpecifier::oArg:
596  case ConversionSpecifier::uArg:
597  case ConversionSpecifier::xArg:
598  case ConversionSpecifier::XArg:
599  case ConversionSpecifier::aArg:
600  case ConversionSpecifier::AArg:
601  case ConversionSpecifier::eArg:
602  case ConversionSpecifier::EArg:
603  case ConversionSpecifier::fArg:
604  case ConversionSpecifier::FArg:
605  case ConversionSpecifier::gArg:
606  case ConversionSpecifier::GArg:
607  case ConversionSpecifier::sArg:
608    return true;
609
610  default:
611    return false;
612  }
613}
614bool PrintfSpecifier::hasValidFieldWidth() const {
615  if (FieldWidth.getHowSpecified() == OptionalAmount::NotSpecified)
616      return true;
617
618  // The field width is valid for all conversions except n
619  switch (CS.getKind()) {
620  case ConversionSpecifier::nArg:
621    return false;
622
623  default:
624    return true;
625  }
626}
627