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 18 using clang::analyze_format_string::ArgTypeResult; 19 using clang::analyze_format_string::FormatStringHandler; 20 using clang::analyze_format_string::LengthModifier; 21 using clang::analyze_format_string::OptionalAmount; 22 using clang::analyze_format_string::ConversionSpecifier; 23 using clang::analyze_printf::PrintfSpecifier; 24 25 using namespace clang; 26 27 typedef clang::analyze_format_string::SpecifierResult<PrintfSpecifier> 28 PrintfSpecifierResult; 29 30 //===----------------------------------------------------------------------===// 31 // Methods for parsing format strings. 32 //===----------------------------------------------------------------------===// 33 34 using analyze_format_string::ParseNonPositionAmount; 35 36 static 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 } else { 42 const OptionalAmount Amt = ParsePositionAmount(H, Start, Beg, E, 43 analyze_format_string::PrecisionPos); 44 if (Amt.isInvalid()) 45 return true; 46 FS.setPrecision(Amt); 47 } 48 return false; 49 } 50 51 static PrintfSpecifierResult ParsePrintfSpecifier(FormatStringHandler &H, 52 const char *&Beg, 53 const char *E, 54 unsigned &argIndex, 55 const LangOptions &LO) { 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 '\'': 104 // FIXME: POSIX specific. Always accept? 105 FS.setHasThousandsGrouping(I); 106 break; 107 case '-': FS.setIsLeftJustified(I); break; 108 case '+': FS.setHasPlusPrefix(I); break; 109 case ' ': FS.setHasSpacePrefix(I); break; 110 case '#': FS.setHasAlternativeForm(I); break; 111 case '0': FS.setHasLeadingZeros(I); break; 112 } 113 if (!hasMore) 114 break; 115 } 116 117 if (I == E) { 118 // No more characters left? 119 H.HandleIncompleteSpecifier(Start, E - Start); 120 return true; 121 } 122 123 // Look for the field width (if any). 124 if (ParseFieldWidth(H, FS, Start, I, E, 125 FS.usesPositionalArg() ? 0 : &argIndex)) 126 return true; 127 128 if (I == E) { 129 // No more characters left? 130 H.HandleIncompleteSpecifier(Start, E - Start); 131 return true; 132 } 133 134 // Look for the precision (if any). 135 if (*I == '.') { 136 ++I; 137 if (I == E) { 138 H.HandleIncompleteSpecifier(Start, E - Start); 139 return true; 140 } 141 142 if (ParsePrecision(H, FS, Start, I, E, 143 FS.usesPositionalArg() ? 0 : &argIndex)) 144 return true; 145 146 if (I == E) { 147 // No more characters left? 148 H.HandleIncompleteSpecifier(Start, E - Start); 149 return true; 150 } 151 } 152 153 // Look for the length modifier. 154 if (ParseLengthModifier(FS, I, E, LO) && I == E) { 155 // No more characters left? 156 H.HandleIncompleteSpecifier(Start, E - Start); 157 return true; 158 } 159 160 if (*I == '\0') { 161 // Detect spurious null characters, which are likely errors. 162 H.HandleNullChar(I); 163 return true; 164 } 165 166 // Finally, look for the conversion specifier. 167 const char *conversionPosition = I++; 168 ConversionSpecifier::Kind k = ConversionSpecifier::InvalidSpecifier; 169 switch (*conversionPosition) { 170 default: 171 break; 172 // C99: 7.19.6.1 (section 8). 173 case '%': k = ConversionSpecifier::PercentArg; break; 174 case 'A': k = ConversionSpecifier::AArg; break; 175 case 'E': k = ConversionSpecifier::EArg; break; 176 case 'F': k = ConversionSpecifier::FArg; break; 177 case 'G': k = ConversionSpecifier::GArg; break; 178 case 'X': k = ConversionSpecifier::XArg; break; 179 case 'a': k = ConversionSpecifier::aArg; break; 180 case 'c': k = ConversionSpecifier::cArg; break; 181 case 'd': k = ConversionSpecifier::dArg; break; 182 case 'e': k = ConversionSpecifier::eArg; break; 183 case 'f': k = ConversionSpecifier::fArg; break; 184 case 'g': k = ConversionSpecifier::gArg; break; 185 case 'i': k = ConversionSpecifier::iArg; break; 186 case 'n': k = ConversionSpecifier::nArg; break; 187 case 'o': k = ConversionSpecifier::oArg; break; 188 case 'p': k = ConversionSpecifier::pArg; break; 189 case 's': k = ConversionSpecifier::sArg; break; 190 case 'u': k = ConversionSpecifier::uArg; break; 191 case 'x': k = ConversionSpecifier::xArg; break; 192 // POSIX specific. 193 case 'C': k = ConversionSpecifier::CArg; break; 194 case 'S': k = ConversionSpecifier::SArg; break; 195 // Objective-C. 196 case '@': k = ConversionSpecifier::ObjCObjArg; break; 197 // Glibc specific. 198 case 'm': k = ConversionSpecifier::PrintErrno; break; 199 } 200 PrintfConversionSpecifier CS(conversionPosition, k); 201 FS.setConversionSpecifier(CS); 202 if (CS.consumesDataArgument() && !FS.usesPositionalArg()) 203 FS.setArgIndex(argIndex++); 204 205 if (k == ConversionSpecifier::InvalidSpecifier) { 206 // Assume the conversion takes one argument. 207 return !H.HandleInvalidPrintfConversionSpecifier(FS, Start, I - Start); 208 } 209 return PrintfSpecifierResult(Start, FS); 210 } 211 212 bool clang::analyze_format_string::ParsePrintfString(FormatStringHandler &H, 213 const char *I, 214 const char *E, 215 const LangOptions &LO) { 216 217 unsigned argIndex = 0; 218 219 // Keep looking for a format specifier until we have exhausted the string. 220 while (I != E) { 221 const PrintfSpecifierResult &FSR = ParsePrintfSpecifier(H, I, E, argIndex, 222 LO); 223 // Did a fail-stop error of any kind occur when parsing the specifier? 224 // If so, don't do any more processing. 225 if (FSR.shouldStop()) 226 return true;; 227 // Did we exhaust the string or encounter an error that 228 // we can recover from? 229 if (!FSR.hasValue()) 230 continue; 231 // We have a format specifier. Pass it to the callback. 232 if (!H.HandlePrintfSpecifier(FSR.getValue(), FSR.getStart(), 233 I - FSR.getStart())) 234 return true; 235 } 236 assert(I == E && "Format string not exhausted"); 237 return false; 238 } 239 240 //===----------------------------------------------------------------------===// 241 // Methods on PrintfSpecifier. 242 //===----------------------------------------------------------------------===// 243 244 ArgTypeResult PrintfSpecifier::getArgType(ASTContext &Ctx, 245 bool IsObjCLiteral) const { 246 const PrintfConversionSpecifier &CS = getConversionSpecifier(); 247 248 if (!CS.consumesDataArgument()) 249 return ArgTypeResult::Invalid(); 250 251 if (CS.getKind() == ConversionSpecifier::cArg) 252 switch (LM.getKind()) { 253 case LengthModifier::None: return Ctx.IntTy; 254 case LengthModifier::AsLong: 255 return ArgTypeResult(ArgTypeResult::WIntTy, "wint_t"); 256 default: 257 return ArgTypeResult::Invalid(); 258 } 259 260 if (CS.isIntArg()) 261 switch (LM.getKind()) { 262 case LengthModifier::AsLongDouble: 263 // GNU extension. 264 return Ctx.LongLongTy; 265 case LengthModifier::None: return Ctx.IntTy; 266 case LengthModifier::AsChar: return ArgTypeResult::AnyCharTy; 267 case LengthModifier::AsShort: return Ctx.ShortTy; 268 case LengthModifier::AsLong: return Ctx.LongTy; 269 case LengthModifier::AsLongLong: 270 case LengthModifier::AsQuad: 271 return Ctx.LongLongTy; 272 case LengthModifier::AsIntMax: 273 return ArgTypeResult(Ctx.getIntMaxType(), "intmax_t"); 274 case LengthModifier::AsSizeT: 275 // FIXME: How to get the corresponding signed version of size_t? 276 return ArgTypeResult(); 277 case LengthModifier::AsPtrDiff: 278 return ArgTypeResult(Ctx.getPointerDiffType(), "ptrdiff_t"); 279 case LengthModifier::AsAllocate: 280 case LengthModifier::AsMAllocate: 281 return ArgTypeResult::Invalid(); 282 } 283 284 if (CS.isUIntArg()) 285 switch (LM.getKind()) { 286 case LengthModifier::AsLongDouble: 287 // GNU extension. 288 return Ctx.UnsignedLongLongTy; 289 case LengthModifier::None: return Ctx.UnsignedIntTy; 290 case LengthModifier::AsChar: return Ctx.UnsignedCharTy; 291 case LengthModifier::AsShort: return Ctx.UnsignedShortTy; 292 case LengthModifier::AsLong: return Ctx.UnsignedLongTy; 293 case LengthModifier::AsLongLong: 294 case LengthModifier::AsQuad: 295 return Ctx.UnsignedLongLongTy; 296 case LengthModifier::AsIntMax: 297 return ArgTypeResult(Ctx.getUIntMaxType(), "uintmax_t"); 298 case LengthModifier::AsSizeT: 299 return ArgTypeResult(Ctx.getSizeType(), "size_t"); 300 case LengthModifier::AsPtrDiff: 301 // FIXME: How to get the corresponding unsigned 302 // version of ptrdiff_t? 303 return ArgTypeResult(); 304 case LengthModifier::AsAllocate: 305 case LengthModifier::AsMAllocate: 306 return ArgTypeResult::Invalid(); 307 } 308 309 if (CS.isDoubleArg()) { 310 if (LM.getKind() == LengthModifier::AsLongDouble) 311 return Ctx.LongDoubleTy; 312 return Ctx.DoubleTy; 313 } 314 315 switch (CS.getKind()) { 316 case ConversionSpecifier::sArg: 317 if (LM.getKind() == LengthModifier::AsWideChar) { 318 if (IsObjCLiteral) 319 return Ctx.getPointerType(Ctx.UnsignedShortTy.withConst()); 320 return ArgTypeResult(ArgTypeResult::WCStrTy, "wchar_t *"); 321 } 322 return ArgTypeResult::CStrTy; 323 case ConversionSpecifier::SArg: 324 if (IsObjCLiteral) 325 return Ctx.getPointerType(Ctx.UnsignedShortTy.withConst()); 326 return ArgTypeResult(ArgTypeResult::WCStrTy, "wchar_t *"); 327 case ConversionSpecifier::CArg: 328 if (IsObjCLiteral) 329 return Ctx.UnsignedShortTy; 330 return ArgTypeResult(Ctx.WCharTy, "wchar_t"); 331 case ConversionSpecifier::pArg: 332 return ArgTypeResult::CPointerTy; 333 case ConversionSpecifier::ObjCObjArg: 334 return ArgTypeResult::ObjCPointerTy; 335 default: 336 break; 337 } 338 339 // FIXME: Handle other cases. 340 return ArgTypeResult(); 341 } 342 343 bool PrintfSpecifier::fixType(QualType QT, const LangOptions &LangOpt, 344 ASTContext &Ctx, bool IsObjCLiteral) { 345 // Handle strings first (char *, wchar_t *) 346 if (QT->isPointerType() && (QT->getPointeeType()->isAnyCharacterType())) { 347 CS.setKind(ConversionSpecifier::sArg); 348 349 // Disable irrelevant flags 350 HasAlternativeForm = 0; 351 HasLeadingZeroes = 0; 352 353 // Set the long length modifier for wide characters 354 if (QT->getPointeeType()->isWideCharType()) 355 LM.setKind(LengthModifier::AsWideChar); 356 else 357 LM.setKind(LengthModifier::None); 358 359 return true; 360 } 361 362 // We can only work with builtin types. 363 const BuiltinType *BT = QT->getAs<BuiltinType>(); 364 if (!BT) 365 return false; 366 367 // Set length modifier 368 switch (BT->getKind()) { 369 case BuiltinType::Bool: 370 case BuiltinType::WChar_U: 371 case BuiltinType::WChar_S: 372 case BuiltinType::Char16: 373 case BuiltinType::Char32: 374 case BuiltinType::UInt128: 375 case BuiltinType::Int128: 376 case BuiltinType::Half: 377 // Various types which are non-trivial to correct. 378 return false; 379 380 #define SIGNED_TYPE(Id, SingletonId) 381 #define UNSIGNED_TYPE(Id, SingletonId) 382 #define FLOATING_TYPE(Id, SingletonId) 383 #define BUILTIN_TYPE(Id, SingletonId) \ 384 case BuiltinType::Id: 385 #include "clang/AST/BuiltinTypes.def" 386 // Misc other stuff which doesn't make sense here. 387 return false; 388 389 case BuiltinType::UInt: 390 case BuiltinType::Int: 391 case BuiltinType::Float: 392 case BuiltinType::Double: 393 LM.setKind(LengthModifier::None); 394 break; 395 396 case BuiltinType::Char_U: 397 case BuiltinType::UChar: 398 case BuiltinType::Char_S: 399 case BuiltinType::SChar: 400 LM.setKind(LengthModifier::AsChar); 401 break; 402 403 case BuiltinType::Short: 404 case BuiltinType::UShort: 405 LM.setKind(LengthModifier::AsShort); 406 break; 407 408 case BuiltinType::Long: 409 case BuiltinType::ULong: 410 LM.setKind(LengthModifier::AsLong); 411 break; 412 413 case BuiltinType::LongLong: 414 case BuiltinType::ULongLong: 415 LM.setKind(LengthModifier::AsLongLong); 416 break; 417 418 case BuiltinType::LongDouble: 419 LM.setKind(LengthModifier::AsLongDouble); 420 break; 421 } 422 423 // Handle size_t, ptrdiff_t, etc. that have dedicated length modifiers in C99. 424 if (isa<TypedefType>(QT) && (LangOpt.C99 || LangOpt.CPlusPlus0x)) { 425 const IdentifierInfo *Identifier = QT.getBaseTypeIdentifier(); 426 if (Identifier->getName() == "size_t") { 427 LM.setKind(LengthModifier::AsSizeT); 428 } else if (Identifier->getName() == "ssize_t") { 429 // Not C99, but common in Unix. 430 LM.setKind(LengthModifier::AsSizeT); 431 } else if (Identifier->getName() == "intmax_t") { 432 LM.setKind(LengthModifier::AsIntMax); 433 } else if (Identifier->getName() == "uintmax_t") { 434 LM.setKind(LengthModifier::AsIntMax); 435 } else if (Identifier->getName() == "ptrdiff_t") { 436 LM.setKind(LengthModifier::AsPtrDiff); 437 } 438 } 439 440 // If fixing the length modifier was enough, we are done. 441 const analyze_printf::ArgTypeResult &ATR = getArgType(Ctx, IsObjCLiteral); 442 if (hasValidLengthModifier() && ATR.isValid() && ATR.matchesType(Ctx, QT)) 443 return true; 444 445 // Set conversion specifier and disable any flags which do not apply to it. 446 // Let typedefs to char fall through to int, as %c is silly for uint8_t. 447 if (isa<TypedefType>(QT) && QT->isAnyCharacterType()) { 448 CS.setKind(ConversionSpecifier::cArg); 449 LM.setKind(LengthModifier::None); 450 Precision.setHowSpecified(OptionalAmount::NotSpecified); 451 HasAlternativeForm = 0; 452 HasLeadingZeroes = 0; 453 HasPlusPrefix = 0; 454 } 455 // Test for Floating type first as LongDouble can pass isUnsignedIntegerType 456 else if (QT->isRealFloatingType()) { 457 CS.setKind(ConversionSpecifier::fArg); 458 } 459 else if (QT->isSignedIntegerType()) { 460 CS.setKind(ConversionSpecifier::dArg); 461 HasAlternativeForm = 0; 462 } 463 else if (QT->isUnsignedIntegerType()) { 464 CS.setKind(ConversionSpecifier::uArg); 465 HasAlternativeForm = 0; 466 HasPlusPrefix = 0; 467 } else { 468 llvm_unreachable("Unexpected type"); 469 } 470 471 return true; 472 } 473 474 void PrintfSpecifier::toString(raw_ostream &os) const { 475 // Whilst some features have no defined order, we are using the order 476 // appearing in the C99 standard (ISO/IEC 9899:1999 (E) 7.19.6.1) 477 os << "%"; 478 479 // Positional args 480 if (usesPositionalArg()) { 481 os << getPositionalArgIndex() << "$"; 482 } 483 484 // Conversion flags 485 if (IsLeftJustified) os << "-"; 486 if (HasPlusPrefix) os << "+"; 487 if (HasSpacePrefix) os << " "; 488 if (HasAlternativeForm) os << "#"; 489 if (HasLeadingZeroes) os << "0"; 490 491 // Minimum field width 492 FieldWidth.toString(os); 493 // Precision 494 Precision.toString(os); 495 // Length modifier 496 os << LM.toString(); 497 // Conversion specifier 498 os << CS.toString(); 499 } 500 501 bool PrintfSpecifier::hasValidPlusPrefix() const { 502 if (!HasPlusPrefix) 503 return true; 504 505 // The plus prefix only makes sense for signed conversions 506 switch (CS.getKind()) { 507 case ConversionSpecifier::dArg: 508 case ConversionSpecifier::iArg: 509 case ConversionSpecifier::fArg: 510 case ConversionSpecifier::FArg: 511 case ConversionSpecifier::eArg: 512 case ConversionSpecifier::EArg: 513 case ConversionSpecifier::gArg: 514 case ConversionSpecifier::GArg: 515 case ConversionSpecifier::aArg: 516 case ConversionSpecifier::AArg: 517 return true; 518 519 default: 520 return false; 521 } 522 } 523 524 bool PrintfSpecifier::hasValidAlternativeForm() const { 525 if (!HasAlternativeForm) 526 return true; 527 528 // Alternate form flag only valid with the oxXaAeEfFgG conversions 529 switch (CS.getKind()) { 530 case ConversionSpecifier::oArg: 531 case ConversionSpecifier::xArg: 532 case ConversionSpecifier::XArg: 533 case ConversionSpecifier::aArg: 534 case ConversionSpecifier::AArg: 535 case ConversionSpecifier::eArg: 536 case ConversionSpecifier::EArg: 537 case ConversionSpecifier::fArg: 538 case ConversionSpecifier::FArg: 539 case ConversionSpecifier::gArg: 540 case ConversionSpecifier::GArg: 541 return true; 542 543 default: 544 return false; 545 } 546 } 547 548 bool PrintfSpecifier::hasValidLeadingZeros() const { 549 if (!HasLeadingZeroes) 550 return true; 551 552 // Leading zeroes flag only valid with the diouxXaAeEfFgG conversions 553 switch (CS.getKind()) { 554 case ConversionSpecifier::dArg: 555 case ConversionSpecifier::iArg: 556 case ConversionSpecifier::oArg: 557 case ConversionSpecifier::uArg: 558 case ConversionSpecifier::xArg: 559 case ConversionSpecifier::XArg: 560 case ConversionSpecifier::aArg: 561 case ConversionSpecifier::AArg: 562 case ConversionSpecifier::eArg: 563 case ConversionSpecifier::EArg: 564 case ConversionSpecifier::fArg: 565 case ConversionSpecifier::FArg: 566 case ConversionSpecifier::gArg: 567 case ConversionSpecifier::GArg: 568 return true; 569 570 default: 571 return false; 572 } 573 } 574 575 bool PrintfSpecifier::hasValidSpacePrefix() const { 576 if (!HasSpacePrefix) 577 return true; 578 579 // The space prefix only makes sense for signed conversions 580 switch (CS.getKind()) { 581 case ConversionSpecifier::dArg: 582 case ConversionSpecifier::iArg: 583 case ConversionSpecifier::fArg: 584 case ConversionSpecifier::FArg: 585 case ConversionSpecifier::eArg: 586 case ConversionSpecifier::EArg: 587 case ConversionSpecifier::gArg: 588 case ConversionSpecifier::GArg: 589 case ConversionSpecifier::aArg: 590 case ConversionSpecifier::AArg: 591 return true; 592 593 default: 594 return false; 595 } 596 } 597 598 bool PrintfSpecifier::hasValidLeftJustified() const { 599 if (!IsLeftJustified) 600 return true; 601 602 // The left justified flag is valid for all conversions except n 603 switch (CS.getKind()) { 604 case ConversionSpecifier::nArg: 605 return false; 606 607 default: 608 return true; 609 } 610 } 611 612 bool PrintfSpecifier::hasValidThousandsGroupingPrefix() const { 613 if (!HasThousandsGrouping) 614 return true; 615 616 switch (CS.getKind()) { 617 case ConversionSpecifier::dArg: 618 case ConversionSpecifier::iArg: 619 case ConversionSpecifier::uArg: 620 case ConversionSpecifier::fArg: 621 case ConversionSpecifier::FArg: 622 case ConversionSpecifier::gArg: 623 case ConversionSpecifier::GArg: 624 return true; 625 default: 626 return false; 627 } 628 } 629 630 bool PrintfSpecifier::hasValidPrecision() const { 631 if (Precision.getHowSpecified() == OptionalAmount::NotSpecified) 632 return true; 633 634 // Precision is only valid with the diouxXaAeEfFgGs conversions 635 switch (CS.getKind()) { 636 case ConversionSpecifier::dArg: 637 case ConversionSpecifier::iArg: 638 case ConversionSpecifier::oArg: 639 case ConversionSpecifier::uArg: 640 case ConversionSpecifier::xArg: 641 case ConversionSpecifier::XArg: 642 case ConversionSpecifier::aArg: 643 case ConversionSpecifier::AArg: 644 case ConversionSpecifier::eArg: 645 case ConversionSpecifier::EArg: 646 case ConversionSpecifier::fArg: 647 case ConversionSpecifier::FArg: 648 case ConversionSpecifier::gArg: 649 case ConversionSpecifier::GArg: 650 case ConversionSpecifier::sArg: 651 return true; 652 653 default: 654 return false; 655 } 656 } 657 bool PrintfSpecifier::hasValidFieldWidth() const { 658 if (FieldWidth.getHowSpecified() == OptionalAmount::NotSpecified) 659 return true; 660 661 // The field width is valid for all conversions except n 662 switch (CS.getKind()) { 663 case ConversionSpecifier::nArg: 664 return false; 665 666 default: 667 return true; 668 } 669 } 670