SemaChecking.cpp revision 12b97ff9ce1412e388444f03049bfa6ad1bb5eb9
1//===--- SemaChecking.cpp - Extra Semantic Checking -----------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements extra semantic analysis beyond what is enforced 11// by the C type system. 12// 13//===----------------------------------------------------------------------===// 14 15#include "Sema.h" 16#include "clang/AST/ASTContext.h" 17#include "clang/AST/DeclObjC.h" 18#include "clang/AST/ExprCXX.h" 19#include "clang/AST/ExprObjC.h" 20#include "clang/Lex/LiteralSupport.h" 21#include "clang/Lex/Preprocessor.h" 22#include <limits> 23using namespace clang; 24 25/// getLocationOfStringLiteralByte - Return a source location that points to the 26/// specified byte of the specified string literal. 27/// 28/// Strings are amazingly complex. They can be formed from multiple tokens and 29/// can have escape sequences in them in addition to the usual trigraph and 30/// escaped newline business. This routine handles this complexity. 31/// 32SourceLocation Sema::getLocationOfStringLiteralByte(const StringLiteral *SL, 33 unsigned ByteNo) const { 34 assert(!SL->isWide() && "This doesn't work for wide strings yet"); 35 36 // Loop over all of the tokens in this string until we find the one that 37 // contains the byte we're looking for. 38 unsigned TokNo = 0; 39 while (1) { 40 assert(TokNo < SL->getNumConcatenated() && "Invalid byte number!"); 41 SourceLocation StrTokLoc = SL->getStrTokenLoc(TokNo); 42 43 // Get the spelling of the string so that we can get the data that makes up 44 // the string literal, not the identifier for the macro it is potentially 45 // expanded through. 46 SourceLocation StrTokSpellingLoc = SourceMgr.getSpellingLoc(StrTokLoc); 47 48 // Re-lex the token to get its length and original spelling. 49 std::pair<FileID, unsigned> LocInfo = 50 SourceMgr.getDecomposedLoc(StrTokSpellingLoc); 51 std::pair<const char *,const char *> Buffer = 52 SourceMgr.getBufferData(LocInfo.first); 53 const char *StrData = Buffer.first+LocInfo.second; 54 55 // Create a langops struct and enable trigraphs. This is sufficient for 56 // relexing tokens. 57 LangOptions LangOpts; 58 LangOpts.Trigraphs = true; 59 60 // Create a lexer starting at the beginning of this token. 61 Lexer TheLexer(StrTokSpellingLoc, LangOpts, Buffer.first, StrData, 62 Buffer.second); 63 Token TheTok; 64 TheLexer.LexFromRawLexer(TheTok); 65 66 // Use the StringLiteralParser to compute the length of the string in bytes. 67 StringLiteralParser SLP(&TheTok, 1, PP); 68 unsigned TokNumBytes = SLP.GetStringLength(); 69 70 // If the byte is in this token, return the location of the byte. 71 if (ByteNo < TokNumBytes || 72 (ByteNo == TokNumBytes && TokNo == SL->getNumConcatenated())) { 73 unsigned Offset = 74 StringLiteralParser::getOffsetOfStringByte(TheTok, ByteNo, PP); 75 76 // Now that we know the offset of the token in the spelling, use the 77 // preprocessor to get the offset in the original source. 78 return PP.AdvanceToTokenCharacter(StrTokLoc, Offset); 79 } 80 81 // Move to the next string token. 82 ++TokNo; 83 ByteNo -= TokNumBytes; 84 } 85} 86 87 88/// CheckFunctionCall - Check a direct function call for various correctness 89/// and safety properties not strictly enforced by the C type system. 90Action::OwningExprResult 91Sema::CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall) { 92 OwningExprResult TheCallResult(Owned(TheCall)); 93 // Get the IdentifierInfo* for the called function. 94 IdentifierInfo *FnInfo = FDecl->getIdentifier(); 95 96 // None of the checks below are needed for functions that don't have 97 // simple names (e.g., C++ conversion functions). 98 if (!FnInfo) 99 return move(TheCallResult); 100 101 switch (FDecl->getBuiltinID(Context)) { 102 case Builtin::BI__builtin___CFStringMakeConstantString: 103 assert(TheCall->getNumArgs() == 1 && 104 "Wrong # arguments to builtin CFStringMakeConstantString"); 105 if (CheckObjCString(TheCall->getArg(0))) 106 return ExprError(); 107 return move(TheCallResult); 108 case Builtin::BI__builtin_stdarg_start: 109 case Builtin::BI__builtin_va_start: 110 if (SemaBuiltinVAStart(TheCall)) 111 return ExprError(); 112 return move(TheCallResult); 113 case Builtin::BI__builtin_isgreater: 114 case Builtin::BI__builtin_isgreaterequal: 115 case Builtin::BI__builtin_isless: 116 case Builtin::BI__builtin_islessequal: 117 case Builtin::BI__builtin_islessgreater: 118 case Builtin::BI__builtin_isunordered: 119 if (SemaBuiltinUnorderedCompare(TheCall)) 120 return ExprError(); 121 return move(TheCallResult); 122 case Builtin::BI__builtin_return_address: 123 case Builtin::BI__builtin_frame_address: 124 if (SemaBuiltinStackAddress(TheCall)) 125 return ExprError(); 126 return move(TheCallResult); 127 case Builtin::BI__builtin_shufflevector: 128 return SemaBuiltinShuffleVector(TheCall); 129 // TheCall will be freed by the smart pointer here, but that's fine, since 130 // SemaBuiltinShuffleVector guts it, but then doesn't release it. 131 case Builtin::BI__builtin_prefetch: 132 if (SemaBuiltinPrefetch(TheCall)) 133 return ExprError(); 134 return move(TheCallResult); 135 case Builtin::BI__builtin_object_size: 136 if (SemaBuiltinObjectSize(TheCall)) 137 return ExprError(); 138 return move(TheCallResult); 139 case Builtin::BI__builtin_longjmp: 140 if (SemaBuiltinLongjmp(TheCall)) 141 return ExprError(); 142 return move(TheCallResult); 143 case Builtin::BI__sync_fetch_and_add: 144 case Builtin::BI__sync_fetch_and_sub: 145 case Builtin::BI__sync_fetch_and_or: 146 case Builtin::BI__sync_fetch_and_and: 147 case Builtin::BI__sync_fetch_and_xor: 148 case Builtin::BI__sync_fetch_and_nand: 149 case Builtin::BI__sync_add_and_fetch: 150 case Builtin::BI__sync_sub_and_fetch: 151 case Builtin::BI__sync_and_and_fetch: 152 case Builtin::BI__sync_or_and_fetch: 153 case Builtin::BI__sync_xor_and_fetch: 154 case Builtin::BI__sync_nand_and_fetch: 155 case Builtin::BI__sync_val_compare_and_swap: 156 case Builtin::BI__sync_bool_compare_and_swap: 157 case Builtin::BI__sync_lock_test_and_set: 158 case Builtin::BI__sync_lock_release: 159 if (SemaBuiltinAtomicOverloaded(TheCall)) 160 return ExprError(); 161 return move(TheCallResult); 162 } 163 164 // FIXME: This mechanism should be abstracted to be less fragile and 165 // more efficient. For example, just map function ids to custom 166 // handlers. 167 168 // Printf checking. 169 if (const FormatAttr *Format = FDecl->getAttr<FormatAttr>()) { 170 if (Format->getType() == "printf") { 171 bool HasVAListArg = Format->getFirstArg() == 0; 172 if (!HasVAListArg) { 173 if (const FunctionProtoType *Proto 174 = FDecl->getType()->getAsFunctionProtoType()) 175 HasVAListArg = !Proto->isVariadic(); 176 } 177 CheckPrintfArguments(TheCall, HasVAListArg, Format->getFormatIdx() - 1, 178 HasVAListArg ? 0 : Format->getFirstArg() - 1); 179 } 180 } 181 for (const Attr *attr = FDecl->getAttrs(); attr; attr = attr->getNext()) { 182 if (const NonNullAttr *NonNull = dyn_cast<NonNullAttr>(attr)) 183 CheckNonNullArguments(NonNull, TheCall); 184 } 185 186 return move(TheCallResult); 187} 188 189Action::OwningExprResult 190Sema::CheckBlockCall(NamedDecl *NDecl, CallExpr *TheCall) { 191 192 OwningExprResult TheCallResult(Owned(TheCall)); 193 // Printf checking. 194 const FormatAttr *Format = NDecl->getAttr<FormatAttr>(); 195 if (!Format) 196 return move(TheCallResult); 197 const VarDecl *V = dyn_cast<VarDecl>(NDecl); 198 if (!V) 199 return move(TheCallResult); 200 QualType Ty = V->getType(); 201 if (!Ty->isBlockPointerType()) 202 return move(TheCallResult); 203 if (Format->getType() == "printf") { 204 bool HasVAListArg = Format->getFirstArg() == 0; 205 if (!HasVAListArg) { 206 const FunctionType *FT = 207 Ty->getAsBlockPointerType()->getPointeeType()->getAsFunctionType(); 208 if (const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT)) 209 HasVAListArg = !Proto->isVariadic(); 210 } 211 CheckPrintfArguments(TheCall, HasVAListArg, Format->getFormatIdx() - 1, 212 HasVAListArg ? 0 : Format->getFirstArg() - 1); 213 } 214 return move(TheCallResult); 215} 216 217/// SemaBuiltinAtomicOverloaded - We have a call to a function like 218/// __sync_fetch_and_add, which is an overloaded function based on the pointer 219/// type of its first argument. The main ActOnCallExpr routines have already 220/// promoted the types of arguments because all of these calls are prototyped as 221/// void(...). 222/// 223/// This function goes through and does final semantic checking for these 224/// builtins, 225bool Sema::SemaBuiltinAtomicOverloaded(CallExpr *TheCall) { 226 DeclRefExpr *DRE =cast<DeclRefExpr>(TheCall->getCallee()->IgnoreParenCasts()); 227 FunctionDecl *FDecl = cast<FunctionDecl>(DRE->getDecl()); 228 229 // Ensure that we have at least one argument to do type inference from. 230 if (TheCall->getNumArgs() < 1) 231 return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) 232 << 0 << TheCall->getCallee()->getSourceRange(); 233 234 // Inspect the first argument of the atomic builtin. This should always be 235 // a pointer type, whose element is an integral scalar or pointer type. 236 // Because it is a pointer type, we don't have to worry about any implicit 237 // casts here. 238 Expr *FirstArg = TheCall->getArg(0); 239 if (!FirstArg->getType()->isPointerType()) 240 return Diag(DRE->getLocStart(), diag::err_atomic_builtin_must_be_pointer) 241 << FirstArg->getType() << FirstArg->getSourceRange(); 242 243 QualType ValType = FirstArg->getType()->getAsPointerType()->getPointeeType(); 244 if (!ValType->isIntegerType() && !ValType->isPointerType() && 245 !ValType->isBlockPointerType()) 246 return Diag(DRE->getLocStart(), 247 diag::err_atomic_builtin_must_be_pointer_intptr) 248 << FirstArg->getType() << FirstArg->getSourceRange(); 249 250 // We need to figure out which concrete builtin this maps onto. For example, 251 // __sync_fetch_and_add with a 2 byte object turns into 252 // __sync_fetch_and_add_2. 253#define BUILTIN_ROW(x) \ 254 { Builtin::BI##x##_1, Builtin::BI##x##_2, Builtin::BI##x##_4, \ 255 Builtin::BI##x##_8, Builtin::BI##x##_16 } 256 257 static const unsigned BuiltinIndices[][5] = { 258 BUILTIN_ROW(__sync_fetch_and_add), 259 BUILTIN_ROW(__sync_fetch_and_sub), 260 BUILTIN_ROW(__sync_fetch_and_or), 261 BUILTIN_ROW(__sync_fetch_and_and), 262 BUILTIN_ROW(__sync_fetch_and_xor), 263 BUILTIN_ROW(__sync_fetch_and_nand), 264 265 BUILTIN_ROW(__sync_add_and_fetch), 266 BUILTIN_ROW(__sync_sub_and_fetch), 267 BUILTIN_ROW(__sync_and_and_fetch), 268 BUILTIN_ROW(__sync_or_and_fetch), 269 BUILTIN_ROW(__sync_xor_and_fetch), 270 BUILTIN_ROW(__sync_nand_and_fetch), 271 272 BUILTIN_ROW(__sync_val_compare_and_swap), 273 BUILTIN_ROW(__sync_bool_compare_and_swap), 274 BUILTIN_ROW(__sync_lock_test_and_set), 275 BUILTIN_ROW(__sync_lock_release) 276 }; 277#undef BUILTIN_ROW 278 279 // Determine the index of the size. 280 unsigned SizeIndex; 281 switch (Context.getTypeSize(ValType)/8) { 282 case 1: SizeIndex = 0; break; 283 case 2: SizeIndex = 1; break; 284 case 4: SizeIndex = 2; break; 285 case 8: SizeIndex = 3; break; 286 case 16: SizeIndex = 4; break; 287 default: 288 return Diag(DRE->getLocStart(), diag::err_atomic_builtin_pointer_size) 289 << FirstArg->getType() << FirstArg->getSourceRange(); 290 } 291 292 // Each of these builtins has one pointer argument, followed by some number of 293 // values (0, 1 or 2) followed by a potentially empty varags list of stuff 294 // that we ignore. Find out which row of BuiltinIndices to read from as well 295 // as the number of fixed args. 296 unsigned BuiltinID = FDecl->getBuiltinID(Context); 297 unsigned BuiltinIndex, NumFixed = 1; 298 switch (BuiltinID) { 299 default: assert(0 && "Unknown overloaded atomic builtin!"); 300 case Builtin::BI__sync_fetch_and_add: BuiltinIndex = 0; break; 301 case Builtin::BI__sync_fetch_and_sub: BuiltinIndex = 1; break; 302 case Builtin::BI__sync_fetch_and_or: BuiltinIndex = 2; break; 303 case Builtin::BI__sync_fetch_and_and: BuiltinIndex = 3; break; 304 case Builtin::BI__sync_fetch_and_xor: BuiltinIndex = 4; break; 305 case Builtin::BI__sync_fetch_and_nand:BuiltinIndex = 5; break; 306 307 case Builtin::BI__sync_add_and_fetch: BuiltinIndex = 6; break; 308 case Builtin::BI__sync_sub_and_fetch: BuiltinIndex = 7; break; 309 case Builtin::BI__sync_and_and_fetch: BuiltinIndex = 8; break; 310 case Builtin::BI__sync_or_and_fetch: BuiltinIndex = 9; break; 311 case Builtin::BI__sync_xor_and_fetch: BuiltinIndex =10; break; 312 case Builtin::BI__sync_nand_and_fetch:BuiltinIndex =11; break; 313 314 case Builtin::BI__sync_val_compare_and_swap: 315 BuiltinIndex = 12; 316 NumFixed = 2; 317 break; 318 case Builtin::BI__sync_bool_compare_and_swap: 319 BuiltinIndex = 13; 320 NumFixed = 2; 321 break; 322 case Builtin::BI__sync_lock_test_and_set: BuiltinIndex = 14; break; 323 case Builtin::BI__sync_lock_release: 324 BuiltinIndex = 15; 325 NumFixed = 0; 326 break; 327 } 328 329 // Now that we know how many fixed arguments we expect, first check that we 330 // have at least that many. 331 if (TheCall->getNumArgs() < 1+NumFixed) 332 return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) 333 << 0 << TheCall->getCallee()->getSourceRange(); 334 335 336 // Get the decl for the concrete builtin from this, we can tell what the 337 // concrete integer type we should convert to is. 338 unsigned NewBuiltinID = BuiltinIndices[BuiltinIndex][SizeIndex]; 339 const char *NewBuiltinName = Context.BuiltinInfo.GetName(NewBuiltinID); 340 IdentifierInfo *NewBuiltinII = PP.getIdentifierInfo(NewBuiltinName); 341 FunctionDecl *NewBuiltinDecl = 342 cast<FunctionDecl>(LazilyCreateBuiltin(NewBuiltinII, NewBuiltinID, 343 TUScope, false, DRE->getLocStart())); 344 const FunctionProtoType *BuiltinFT = 345 NewBuiltinDecl->getType()->getAsFunctionProtoType(); 346 ValType = BuiltinFT->getArgType(0)->getAsPointerType()->getPointeeType(); 347 348 // If the first type needs to be converted (e.g. void** -> int*), do it now. 349 if (BuiltinFT->getArgType(0) != FirstArg->getType()) { 350 ImpCastExprToType(FirstArg, BuiltinFT->getArgType(0), false); 351 TheCall->setArg(0, FirstArg); 352 } 353 354 // Next, walk the valid ones promoting to the right type. 355 for (unsigned i = 0; i != NumFixed; ++i) { 356 Expr *Arg = TheCall->getArg(i+1); 357 358 // If the argument is an implicit cast, then there was a promotion due to 359 // "...", just remove it now. 360 if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Arg)) { 361 Arg = ICE->getSubExpr(); 362 ICE->setSubExpr(0); 363 ICE->Destroy(Context); 364 TheCall->setArg(i+1, Arg); 365 } 366 367 // GCC does an implicit conversion to the pointer or integer ValType. This 368 // can fail in some cases (1i -> int**), check for this error case now. 369 if (CheckCastTypes(Arg->getSourceRange(), ValType, Arg)) 370 return true; 371 372 // Okay, we have something that *can* be converted to the right type. Check 373 // to see if there is a potentially weird extension going on here. This can 374 // happen when you do an atomic operation on something like an char* and 375 // pass in 42. The 42 gets converted to char. This is even more strange 376 // for things like 45.123 -> char, etc. 377 // FIXME: Do this check. 378 ImpCastExprToType(Arg, ValType, false); 379 TheCall->setArg(i+1, Arg); 380 } 381 382 // Switch the DeclRefExpr to refer to the new decl. 383 DRE->setDecl(NewBuiltinDecl); 384 DRE->setType(NewBuiltinDecl->getType()); 385 386 // Set the callee in the CallExpr. 387 // FIXME: This leaks the original parens and implicit casts. 388 Expr *PromotedCall = DRE; 389 UsualUnaryConversions(PromotedCall); 390 TheCall->setCallee(PromotedCall); 391 392 393 // Change the result type of the call to match the result type of the decl. 394 TheCall->setType(NewBuiltinDecl->getResultType()); 395 return false; 396} 397 398 399/// CheckObjCString - Checks that the argument to the builtin 400/// CFString constructor is correct 401/// FIXME: GCC currently emits the following warning: 402/// "warning: input conversion stopped due to an input byte that does not 403/// belong to the input codeset UTF-8" 404/// Note: It might also make sense to do the UTF-16 conversion here (would 405/// simplify the backend). 406bool Sema::CheckObjCString(Expr *Arg) { 407 Arg = Arg->IgnoreParenCasts(); 408 StringLiteral *Literal = dyn_cast<StringLiteral>(Arg); 409 410 if (!Literal || Literal->isWide()) { 411 Diag(Arg->getLocStart(), diag::err_cfstring_literal_not_string_constant) 412 << Arg->getSourceRange(); 413 return true; 414 } 415 416 const char *Data = Literal->getStrData(); 417 unsigned Length = Literal->getByteLength(); 418 419 for (unsigned i = 0; i < Length; ++i) { 420 if (!Data[i]) { 421 Diag(getLocationOfStringLiteralByte(Literal, i), 422 diag::warn_cfstring_literal_contains_nul_character) 423 << Arg->getSourceRange(); 424 break; 425 } 426 } 427 428 return false; 429} 430 431/// SemaBuiltinVAStart - Check the arguments to __builtin_va_start for validity. 432/// Emit an error and return true on failure, return false on success. 433bool Sema::SemaBuiltinVAStart(CallExpr *TheCall) { 434 Expr *Fn = TheCall->getCallee(); 435 if (TheCall->getNumArgs() > 2) { 436 Diag(TheCall->getArg(2)->getLocStart(), 437 diag::err_typecheck_call_too_many_args) 438 << 0 /*function call*/ << Fn->getSourceRange() 439 << SourceRange(TheCall->getArg(2)->getLocStart(), 440 (*(TheCall->arg_end()-1))->getLocEnd()); 441 return true; 442 } 443 444 if (TheCall->getNumArgs() < 2) { 445 return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) 446 << 0 /*function call*/; 447 } 448 449 // Determine whether the current function is variadic or not. 450 bool isVariadic; 451 if (CurBlock) 452 isVariadic = CurBlock->isVariadic; 453 else if (getCurFunctionDecl()) { 454 if (FunctionProtoType* FTP = 455 dyn_cast<FunctionProtoType>(getCurFunctionDecl()->getType())) 456 isVariadic = FTP->isVariadic(); 457 else 458 isVariadic = false; 459 } else { 460 isVariadic = getCurMethodDecl()->isVariadic(); 461 } 462 463 if (!isVariadic) { 464 Diag(Fn->getLocStart(), diag::err_va_start_used_in_non_variadic_function); 465 return true; 466 } 467 468 // Verify that the second argument to the builtin is the last argument of the 469 // current function or method. 470 bool SecondArgIsLastNamedArgument = false; 471 const Expr *Arg = TheCall->getArg(1)->IgnoreParenCasts(); 472 473 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Arg)) { 474 if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(DR->getDecl())) { 475 // FIXME: This isn't correct for methods (results in bogus warning). 476 // Get the last formal in the current function. 477 const ParmVarDecl *LastArg; 478 if (CurBlock) 479 LastArg = *(CurBlock->TheDecl->param_end()-1); 480 else if (FunctionDecl *FD = getCurFunctionDecl()) 481 LastArg = *(FD->param_end()-1); 482 else 483 LastArg = *(getCurMethodDecl()->param_end()-1); 484 SecondArgIsLastNamedArgument = PV == LastArg; 485 } 486 } 487 488 if (!SecondArgIsLastNamedArgument) 489 Diag(TheCall->getArg(1)->getLocStart(), 490 diag::warn_second_parameter_of_va_start_not_last_named_argument); 491 return false; 492} 493 494/// SemaBuiltinUnorderedCompare - Handle functions like __builtin_isgreater and 495/// friends. This is declared to take (...), so we have to check everything. 496bool Sema::SemaBuiltinUnorderedCompare(CallExpr *TheCall) { 497 if (TheCall->getNumArgs() < 2) 498 return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) 499 << 0 /*function call*/; 500 if (TheCall->getNumArgs() > 2) 501 return Diag(TheCall->getArg(2)->getLocStart(), 502 diag::err_typecheck_call_too_many_args) 503 << 0 /*function call*/ 504 << SourceRange(TheCall->getArg(2)->getLocStart(), 505 (*(TheCall->arg_end()-1))->getLocEnd()); 506 507 Expr *OrigArg0 = TheCall->getArg(0); 508 Expr *OrigArg1 = TheCall->getArg(1); 509 510 // Do standard promotions between the two arguments, returning their common 511 // type. 512 QualType Res = UsualArithmeticConversions(OrigArg0, OrigArg1, false); 513 514 // Make sure any conversions are pushed back into the call; this is 515 // type safe since unordered compare builtins are declared as "_Bool 516 // foo(...)". 517 TheCall->setArg(0, OrigArg0); 518 TheCall->setArg(1, OrigArg1); 519 520 if (OrigArg0->isTypeDependent() || OrigArg1->isTypeDependent()) 521 return false; 522 523 // If the common type isn't a real floating type, then the arguments were 524 // invalid for this operation. 525 if (!Res->isRealFloatingType()) 526 return Diag(OrigArg0->getLocStart(), 527 diag::err_typecheck_call_invalid_ordered_compare) 528 << OrigArg0->getType() << OrigArg1->getType() 529 << SourceRange(OrigArg0->getLocStart(), OrigArg1->getLocEnd()); 530 531 return false; 532} 533 534bool Sema::SemaBuiltinStackAddress(CallExpr *TheCall) { 535 // The signature for these builtins is exact; the only thing we need 536 // to check is that the argument is a constant. 537 SourceLocation Loc; 538 if (!TheCall->getArg(0)->isTypeDependent() && 539 !TheCall->getArg(0)->isValueDependent() && 540 !TheCall->getArg(0)->isIntegerConstantExpr(Context, &Loc)) 541 return Diag(Loc, diag::err_stack_const_level) << TheCall->getSourceRange(); 542 543 return false; 544} 545 546/// SemaBuiltinShuffleVector - Handle __builtin_shufflevector. 547// This is declared to take (...), so we have to check everything. 548Action::OwningExprResult Sema::SemaBuiltinShuffleVector(CallExpr *TheCall) { 549 if (TheCall->getNumArgs() < 3) 550 return ExprError(Diag(TheCall->getLocEnd(), 551 diag::err_typecheck_call_too_few_args) 552 << 0 /*function call*/ << TheCall->getSourceRange()); 553 554 unsigned numElements = std::numeric_limits<unsigned>::max(); 555 if (!TheCall->getArg(0)->isTypeDependent() && 556 !TheCall->getArg(1)->isTypeDependent()) { 557 QualType FAType = TheCall->getArg(0)->getType(); 558 QualType SAType = TheCall->getArg(1)->getType(); 559 560 if (!FAType->isVectorType() || !SAType->isVectorType()) { 561 Diag(TheCall->getLocStart(), diag::err_shufflevector_non_vector) 562 << SourceRange(TheCall->getArg(0)->getLocStart(), 563 TheCall->getArg(1)->getLocEnd()); 564 return ExprError(); 565 } 566 567 if (Context.getCanonicalType(FAType).getUnqualifiedType() != 568 Context.getCanonicalType(SAType).getUnqualifiedType()) { 569 Diag(TheCall->getLocStart(), diag::err_shufflevector_incompatible_vector) 570 << SourceRange(TheCall->getArg(0)->getLocStart(), 571 TheCall->getArg(1)->getLocEnd()); 572 return ExprError(); 573 } 574 575 numElements = FAType->getAsVectorType()->getNumElements(); 576 if (TheCall->getNumArgs() != numElements+2) { 577 if (TheCall->getNumArgs() < numElements+2) 578 return ExprError(Diag(TheCall->getLocEnd(), 579 diag::err_typecheck_call_too_few_args) 580 << 0 /*function call*/ << TheCall->getSourceRange()); 581 return ExprError(Diag(TheCall->getLocEnd(), 582 diag::err_typecheck_call_too_many_args) 583 << 0 /*function call*/ << TheCall->getSourceRange()); 584 } 585 } 586 587 for (unsigned i = 2; i < TheCall->getNumArgs(); i++) { 588 if (TheCall->getArg(i)->isTypeDependent() || 589 TheCall->getArg(i)->isValueDependent()) 590 continue; 591 592 llvm::APSInt Result(32); 593 if (!TheCall->getArg(i)->isIntegerConstantExpr(Result, Context)) 594 return ExprError(Diag(TheCall->getLocStart(), 595 diag::err_shufflevector_nonconstant_argument) 596 << TheCall->getArg(i)->getSourceRange()); 597 598 if (Result.getActiveBits() > 64 || Result.getZExtValue() >= numElements*2) 599 return ExprError(Diag(TheCall->getLocStart(), 600 diag::err_shufflevector_argument_too_large) 601 << TheCall->getArg(i)->getSourceRange()); 602 } 603 604 llvm::SmallVector<Expr*, 32> exprs; 605 606 for (unsigned i = 0, e = TheCall->getNumArgs(); i != e; i++) { 607 exprs.push_back(TheCall->getArg(i)); 608 TheCall->setArg(i, 0); 609 } 610 611 return Owned(new (Context) ShuffleVectorExpr(exprs.begin(), exprs.size(), 612 exprs[0]->getType(), 613 TheCall->getCallee()->getLocStart(), 614 TheCall->getRParenLoc())); 615} 616 617/// SemaBuiltinPrefetch - Handle __builtin_prefetch. 618// This is declared to take (const void*, ...) and can take two 619// optional constant int args. 620bool Sema::SemaBuiltinPrefetch(CallExpr *TheCall) { 621 unsigned NumArgs = TheCall->getNumArgs(); 622 623 if (NumArgs > 3) 624 return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_many_args) 625 << 0 /*function call*/ << TheCall->getSourceRange(); 626 627 // Argument 0 is checked for us and the remaining arguments must be 628 // constant integers. 629 for (unsigned i = 1; i != NumArgs; ++i) { 630 Expr *Arg = TheCall->getArg(i); 631 if (Arg->isTypeDependent()) 632 continue; 633 634 QualType RWType = Arg->getType(); 635 636 const BuiltinType *BT = RWType->getAsBuiltinType(); 637 llvm::APSInt Result; 638 if (!BT || BT->getKind() != BuiltinType::Int) 639 return Diag(TheCall->getLocStart(), diag::err_prefetch_invalid_argument) 640 << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 641 642 if (Arg->isValueDependent()) 643 continue; 644 645 if (!Arg->isIntegerConstantExpr(Result, Context)) 646 return Diag(TheCall->getLocStart(), diag::err_prefetch_invalid_argument) 647 << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 648 649 // FIXME: gcc issues a warning and rewrites these to 0. These 650 // seems especially odd for the third argument since the default 651 // is 3. 652 if (i == 1) { 653 if (Result.getSExtValue() < 0 || Result.getSExtValue() > 1) 654 return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) 655 << "0" << "1" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 656 } else { 657 if (Result.getSExtValue() < 0 || Result.getSExtValue() > 3) 658 return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) 659 << "0" << "3" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 660 } 661 } 662 663 return false; 664} 665 666/// SemaBuiltinObjectSize - Handle __builtin_object_size(void *ptr, 667/// int type). This simply type checks that type is one of the defined 668/// constants (0-3). 669bool Sema::SemaBuiltinObjectSize(CallExpr *TheCall) { 670 Expr *Arg = TheCall->getArg(1); 671 if (Arg->isTypeDependent()) 672 return false; 673 674 QualType ArgType = Arg->getType(); 675 const BuiltinType *BT = ArgType->getAsBuiltinType(); 676 llvm::APSInt Result(32); 677 if (!BT || BT->getKind() != BuiltinType::Int) 678 return Diag(TheCall->getLocStart(), diag::err_object_size_invalid_argument) 679 << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 680 681 if (Arg->isValueDependent()) 682 return false; 683 684 if (!Arg->isIntegerConstantExpr(Result, Context)) { 685 return Diag(TheCall->getLocStart(), diag::err_object_size_invalid_argument) 686 << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 687 } 688 689 if (Result.getSExtValue() < 0 || Result.getSExtValue() > 3) { 690 return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) 691 << "0" << "3" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 692 } 693 694 return false; 695} 696 697/// SemaBuiltinLongjmp - Handle __builtin_longjmp(void *env[5], int val). 698/// This checks that val is a constant 1. 699bool Sema::SemaBuiltinLongjmp(CallExpr *TheCall) { 700 Expr *Arg = TheCall->getArg(1); 701 if (Arg->isTypeDependent() || Arg->isValueDependent()) 702 return false; 703 704 llvm::APSInt Result(32); 705 if (!Arg->isIntegerConstantExpr(Result, Context) || Result != 1) 706 return Diag(TheCall->getLocStart(), diag::err_builtin_longjmp_invalid_val) 707 << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); 708 709 return false; 710} 711 712// Handle i > 1 ? "x" : "y", recursivelly 713bool Sema::SemaCheckStringLiteral(const Expr *E, const CallExpr *TheCall, 714 bool HasVAListArg, 715 unsigned format_idx, unsigned firstDataArg) { 716 if (E->isTypeDependent() || E->isValueDependent()) 717 return false; 718 719 switch (E->getStmtClass()) { 720 case Stmt::ConditionalOperatorClass: { 721 const ConditionalOperator *C = cast<ConditionalOperator>(E); 722 return SemaCheckStringLiteral(C->getLHS(), TheCall, 723 HasVAListArg, format_idx, firstDataArg) 724 && SemaCheckStringLiteral(C->getRHS(), TheCall, 725 HasVAListArg, format_idx, firstDataArg); 726 } 727 728 case Stmt::ImplicitCastExprClass: { 729 const ImplicitCastExpr *Expr = cast<ImplicitCastExpr>(E); 730 return SemaCheckStringLiteral(Expr->getSubExpr(), TheCall, HasVAListArg, 731 format_idx, firstDataArg); 732 } 733 734 case Stmt::ParenExprClass: { 735 const ParenExpr *Expr = cast<ParenExpr>(E); 736 return SemaCheckStringLiteral(Expr->getSubExpr(), TheCall, HasVAListArg, 737 format_idx, firstDataArg); 738 } 739 740 case Stmt::DeclRefExprClass: { 741 const DeclRefExpr *DR = cast<DeclRefExpr>(E); 742 743 // As an exception, do not flag errors for variables binding to 744 // const string literals. 745 if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) { 746 bool isConstant = false; 747 QualType T = DR->getType(); 748 749 if (const ArrayType *AT = Context.getAsArrayType(T)) { 750 isConstant = AT->getElementType().isConstant(Context); 751 } 752 else if (const PointerType *PT = T->getAsPointerType()) { 753 isConstant = T.isConstant(Context) && 754 PT->getPointeeType().isConstant(Context); 755 } 756 757 if (isConstant) { 758 const VarDecl *Def = 0; 759 if (const Expr *Init = VD->getDefinition(Def)) 760 return SemaCheckStringLiteral(Init, TheCall, 761 HasVAListArg, format_idx, firstDataArg); 762 } 763 } 764 765 return false; 766 } 767 768 case Stmt::ObjCStringLiteralClass: 769 case Stmt::StringLiteralClass: { 770 const StringLiteral *StrE = NULL; 771 772 if (const ObjCStringLiteral *ObjCFExpr = dyn_cast<ObjCStringLiteral>(E)) 773 StrE = ObjCFExpr->getString(); 774 else 775 StrE = cast<StringLiteral>(E); 776 777 if (StrE) { 778 CheckPrintfString(StrE, E, TheCall, HasVAListArg, format_idx, 779 firstDataArg); 780 return true; 781 } 782 783 return false; 784 } 785 786 default: 787 return false; 788 } 789} 790 791void 792Sema::CheckNonNullArguments(const NonNullAttr *NonNull, const CallExpr *TheCall) 793{ 794 for (NonNullAttr::iterator i = NonNull->begin(), e = NonNull->end(); 795 i != e; ++i) { 796 const Expr *ArgExpr = TheCall->getArg(*i); 797 if (ArgExpr->isNullPointerConstant(Context)) 798 Diag(TheCall->getCallee()->getLocStart(), diag::warn_null_arg) 799 << ArgExpr->getSourceRange(); 800 } 801} 802 803/// CheckPrintfArguments - Check calls to printf (and similar functions) for 804/// correct use of format strings. 805/// 806/// HasVAListArg - A predicate indicating whether the printf-like 807/// function is passed an explicit va_arg argument (e.g., vprintf) 808/// 809/// format_idx - The index into Args for the format string. 810/// 811/// Improper format strings to functions in the printf family can be 812/// the source of bizarre bugs and very serious security holes. A 813/// good source of information is available in the following paper 814/// (which includes additional references): 815/// 816/// FormatGuard: Automatic Protection From printf Format String 817/// Vulnerabilities, Proceedings of the 10th USENIX Security Symposium, 2001. 818/// 819/// Functionality implemented: 820/// 821/// We can statically check the following properties for string 822/// literal format strings for non v.*printf functions (where the 823/// arguments are passed directly): 824// 825/// (1) Are the number of format conversions equal to the number of 826/// data arguments? 827/// 828/// (2) Does each format conversion correctly match the type of the 829/// corresponding data argument? (TODO) 830/// 831/// Moreover, for all printf functions we can: 832/// 833/// (3) Check for a missing format string (when not caught by type checking). 834/// 835/// (4) Check for no-operation flags; e.g. using "#" with format 836/// conversion 'c' (TODO) 837/// 838/// (5) Check the use of '%n', a major source of security holes. 839/// 840/// (6) Check for malformed format conversions that don't specify anything. 841/// 842/// (7) Check for empty format strings. e.g: printf(""); 843/// 844/// (8) Check that the format string is a wide literal. 845/// 846/// (9) Also check the arguments of functions with the __format__ attribute. 847/// (TODO). 848/// 849/// All of these checks can be done by parsing the format string. 850/// 851/// For now, we ONLY do (1), (3), (5), (6), (7), and (8). 852void 853Sema::CheckPrintfArguments(const CallExpr *TheCall, bool HasVAListArg, 854 unsigned format_idx, unsigned firstDataArg) { 855 const Expr *Fn = TheCall->getCallee(); 856 857 // CHECK: printf-like function is called with no format string. 858 if (format_idx >= TheCall->getNumArgs()) { 859 Diag(TheCall->getRParenLoc(), diag::warn_printf_missing_format_string) 860 << Fn->getSourceRange(); 861 return; 862 } 863 864 const Expr *OrigFormatExpr = TheCall->getArg(format_idx)->IgnoreParenCasts(); 865 866 // CHECK: format string is not a string literal. 867 // 868 // Dynamically generated format strings are difficult to 869 // automatically vet at compile time. Requiring that format strings 870 // are string literals: (1) permits the checking of format strings by 871 // the compiler and thereby (2) can practically remove the source of 872 // many format string exploits. 873 874 // Format string can be either ObjC string (e.g. @"%d") or 875 // C string (e.g. "%d") 876 // ObjC string uses the same format specifiers as C string, so we can use 877 // the same format string checking logic for both ObjC and C strings. 878 if (SemaCheckStringLiteral(OrigFormatExpr, TheCall, HasVAListArg, format_idx, 879 firstDataArg)) 880 return; // Literal format string found, check done! 881 882 // For vprintf* functions (i.e., HasVAListArg==true), we add a 883 // special check to see if the format string is a function parameter 884 // of the function calling the printf function. If the function 885 // has an attribute indicating it is a printf-like function, then we 886 // should suppress warnings concerning non-literals being used in a call 887 // to a vprintf function. For example: 888 // 889 // void 890 // logmessage(char const *fmt __attribute__ (format (printf, 1, 2)), ...) { 891 // va_list ap; 892 // va_start(ap, fmt); 893 // vprintf(fmt, ap); // Do NOT emit a warning about "fmt". 894 // ... 895 // 896 // 897 // FIXME: We don't have full attribute support yet, so just check to see 898 // if the argument is a DeclRefExpr that references a parameter. We'll 899 // add proper support for checking the attribute later. 900 if (HasVAListArg) 901 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(OrigFormatExpr)) 902 if (isa<ParmVarDecl>(DR->getDecl())) 903 return; 904 905 // If there are no arguments specified, warn with -Wformat-security, otherwise 906 // warn only with -Wformat-nonliteral. 907 if (TheCall->getNumArgs() == format_idx+1) 908 Diag(TheCall->getArg(format_idx)->getLocStart(), 909 diag::warn_printf_nonliteral_noargs) 910 << OrigFormatExpr->getSourceRange(); 911 else 912 Diag(TheCall->getArg(format_idx)->getLocStart(), 913 diag::warn_printf_nonliteral) 914 << OrigFormatExpr->getSourceRange(); 915} 916 917void Sema::CheckPrintfString(const StringLiteral *FExpr, 918 const Expr *OrigFormatExpr, 919 const CallExpr *TheCall, bool HasVAListArg, 920 unsigned format_idx, unsigned firstDataArg) { 921 922 const ObjCStringLiteral *ObjCFExpr = 923 dyn_cast<ObjCStringLiteral>(OrigFormatExpr); 924 925 // CHECK: is the format string a wide literal? 926 if (FExpr->isWide()) { 927 Diag(FExpr->getLocStart(), 928 diag::warn_printf_format_string_is_wide_literal) 929 << OrigFormatExpr->getSourceRange(); 930 return; 931 } 932 933 // Str - The format string. NOTE: this is NOT null-terminated! 934 const char *Str = FExpr->getStrData(); 935 936 // CHECK: empty format string? 937 unsigned StrLen = FExpr->getByteLength(); 938 939 if (StrLen == 0) { 940 Diag(FExpr->getLocStart(), diag::warn_printf_empty_format_string) 941 << OrigFormatExpr->getSourceRange(); 942 return; 943 } 944 945 // We process the format string using a binary state machine. The 946 // current state is stored in CurrentState. 947 enum { 948 state_OrdChr, 949 state_Conversion 950 } CurrentState = state_OrdChr; 951 952 // numConversions - The number of conversions seen so far. This is 953 // incremented as we traverse the format string. 954 unsigned numConversions = 0; 955 956 // numDataArgs - The number of data arguments after the format 957 // string. This can only be determined for non vprintf-like 958 // functions. For those functions, this value is 1 (the sole 959 // va_arg argument). 960 unsigned numDataArgs = TheCall->getNumArgs()-firstDataArg; 961 962 // Inspect the format string. 963 unsigned StrIdx = 0; 964 965 // LastConversionIdx - Index within the format string where we last saw 966 // a '%' character that starts a new format conversion. 967 unsigned LastConversionIdx = 0; 968 969 for (; StrIdx < StrLen; ++StrIdx) { 970 971 // Is the number of detected conversion conversions greater than 972 // the number of matching data arguments? If so, stop. 973 if (!HasVAListArg && numConversions > numDataArgs) break; 974 975 // Handle "\0" 976 if (Str[StrIdx] == '\0') { 977 // The string returned by getStrData() is not null-terminated, 978 // so the presence of a null character is likely an error. 979 Diag(getLocationOfStringLiteralByte(FExpr, StrIdx), 980 diag::warn_printf_format_string_contains_null_char) 981 << OrigFormatExpr->getSourceRange(); 982 return; 983 } 984 985 // Ordinary characters (not processing a format conversion). 986 if (CurrentState == state_OrdChr) { 987 if (Str[StrIdx] == '%') { 988 CurrentState = state_Conversion; 989 LastConversionIdx = StrIdx; 990 } 991 continue; 992 } 993 994 // Seen '%'. Now processing a format conversion. 995 switch (Str[StrIdx]) { 996 // Handle dynamic precision or width specifier. 997 case '*': { 998 ++numConversions; 999 1000 if (!HasVAListArg) { 1001 if (numConversions > numDataArgs) { 1002 SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, StrIdx); 1003 1004 if (Str[StrIdx-1] == '.') 1005 Diag(Loc, diag::warn_printf_asterisk_precision_missing_arg) 1006 << OrigFormatExpr->getSourceRange(); 1007 else 1008 Diag(Loc, diag::warn_printf_asterisk_width_missing_arg) 1009 << OrigFormatExpr->getSourceRange(); 1010 1011 // Don't do any more checking. We'll just emit spurious errors. 1012 return; 1013 } 1014 1015 // Perform type checking on width/precision specifier. 1016 const Expr *E = TheCall->getArg(format_idx+numConversions); 1017 if (const BuiltinType *BT = E->getType()->getAsBuiltinType()) 1018 if (BT->getKind() == BuiltinType::Int) 1019 break; 1020 1021 SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, StrIdx); 1022 1023 if (Str[StrIdx-1] == '.') 1024 Diag(Loc, diag::warn_printf_asterisk_precision_wrong_type) 1025 << E->getType() << E->getSourceRange(); 1026 else 1027 Diag(Loc, diag::warn_printf_asterisk_width_wrong_type) 1028 << E->getType() << E->getSourceRange(); 1029 1030 break; 1031 } 1032 } 1033 1034 // Characters which can terminate a format conversion 1035 // (e.g. "%d"). Characters that specify length modifiers or 1036 // other flags are handled by the default case below. 1037 // 1038 // FIXME: additional checks will go into the following cases. 1039 case 'i': 1040 case 'd': 1041 case 'o': 1042 case 'u': 1043 case 'x': 1044 case 'X': 1045 case 'D': 1046 case 'O': 1047 case 'U': 1048 case 'e': 1049 case 'E': 1050 case 'f': 1051 case 'F': 1052 case 'g': 1053 case 'G': 1054 case 'a': 1055 case 'A': 1056 case 'c': 1057 case 'C': 1058 case 'S': 1059 case 's': 1060 case 'p': 1061 ++numConversions; 1062 CurrentState = state_OrdChr; 1063 break; 1064 1065 // CHECK: Are we using "%n"? Issue a warning. 1066 case 'n': { 1067 ++numConversions; 1068 CurrentState = state_OrdChr; 1069 SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, 1070 LastConversionIdx); 1071 1072 Diag(Loc, diag::warn_printf_write_back)<<OrigFormatExpr->getSourceRange(); 1073 break; 1074 } 1075 1076 // Handle "%@" 1077 case '@': 1078 // %@ is allowed in ObjC format strings only. 1079 if(ObjCFExpr != NULL) 1080 CurrentState = state_OrdChr; 1081 else { 1082 // Issue a warning: invalid format conversion. 1083 SourceLocation Loc = 1084 getLocationOfStringLiteralByte(FExpr, LastConversionIdx); 1085 1086 Diag(Loc, diag::warn_printf_invalid_conversion) 1087 << std::string(Str+LastConversionIdx, 1088 Str+std::min(LastConversionIdx+2, StrLen)) 1089 << OrigFormatExpr->getSourceRange(); 1090 } 1091 ++numConversions; 1092 break; 1093 1094 // Handle "%%" 1095 case '%': 1096 // Sanity check: Was the first "%" character the previous one? 1097 // If not, we will assume that we have a malformed format 1098 // conversion, and that the current "%" character is the start 1099 // of a new conversion. 1100 if (StrIdx - LastConversionIdx == 1) 1101 CurrentState = state_OrdChr; 1102 else { 1103 // Issue a warning: invalid format conversion. 1104 SourceLocation Loc = 1105 getLocationOfStringLiteralByte(FExpr, LastConversionIdx); 1106 1107 Diag(Loc, diag::warn_printf_invalid_conversion) 1108 << std::string(Str+LastConversionIdx, Str+StrIdx) 1109 << OrigFormatExpr->getSourceRange(); 1110 1111 // This conversion is broken. Advance to the next format 1112 // conversion. 1113 LastConversionIdx = StrIdx; 1114 ++numConversions; 1115 } 1116 break; 1117 1118 default: 1119 // This case catches all other characters: flags, widths, etc. 1120 // We should eventually process those as well. 1121 break; 1122 } 1123 } 1124 1125 if (CurrentState == state_Conversion) { 1126 // Issue a warning: invalid format conversion. 1127 SourceLocation Loc = 1128 getLocationOfStringLiteralByte(FExpr, LastConversionIdx); 1129 1130 Diag(Loc, diag::warn_printf_invalid_conversion) 1131 << std::string(Str+LastConversionIdx, 1132 Str+std::min(LastConversionIdx+2, StrLen)) 1133 << OrigFormatExpr->getSourceRange(); 1134 return; 1135 } 1136 1137 if (!HasVAListArg) { 1138 // CHECK: Does the number of format conversions exceed the number 1139 // of data arguments? 1140 if (numConversions > numDataArgs) { 1141 SourceLocation Loc = 1142 getLocationOfStringLiteralByte(FExpr, LastConversionIdx); 1143 1144 Diag(Loc, diag::warn_printf_insufficient_data_args) 1145 << OrigFormatExpr->getSourceRange(); 1146 } 1147 // CHECK: Does the number of data arguments exceed the number of 1148 // format conversions in the format string? 1149 else if (numConversions < numDataArgs) 1150 Diag(TheCall->getArg(format_idx+numConversions+1)->getLocStart(), 1151 diag::warn_printf_too_many_data_args) 1152 << OrigFormatExpr->getSourceRange(); 1153 } 1154} 1155 1156//===--- CHECK: Return Address of Stack Variable --------------------------===// 1157 1158static DeclRefExpr* EvalVal(Expr *E); 1159static DeclRefExpr* EvalAddr(Expr* E); 1160 1161/// CheckReturnStackAddr - Check if a return statement returns the address 1162/// of a stack variable. 1163void 1164Sema::CheckReturnStackAddr(Expr *RetValExp, QualType lhsType, 1165 SourceLocation ReturnLoc) { 1166 1167 // Perform checking for returned stack addresses. 1168 if (lhsType->isPointerType() || lhsType->isBlockPointerType()) { 1169 if (DeclRefExpr *DR = EvalAddr(RetValExp)) 1170 Diag(DR->getLocStart(), diag::warn_ret_stack_addr) 1171 << DR->getDecl()->getDeclName() << RetValExp->getSourceRange(); 1172 1173 // Skip over implicit cast expressions when checking for block expressions. 1174 if (ImplicitCastExpr *IcExpr = 1175 dyn_cast_or_null<ImplicitCastExpr>(RetValExp)) 1176 RetValExp = IcExpr->getSubExpr(); 1177 1178 if (BlockExpr *C = dyn_cast_or_null<BlockExpr>(RetValExp)) 1179 if (C->hasBlockDeclRefExprs()) 1180 Diag(C->getLocStart(), diag::err_ret_local_block) 1181 << C->getSourceRange(); 1182 } 1183 // Perform checking for stack values returned by reference. 1184 else if (lhsType->isReferenceType()) { 1185 // Check for a reference to the stack 1186 if (DeclRefExpr *DR = EvalVal(RetValExp)) 1187 Diag(DR->getLocStart(), diag::warn_ret_stack_ref) 1188 << DR->getDecl()->getDeclName() << RetValExp->getSourceRange(); 1189 } 1190} 1191 1192/// EvalAddr - EvalAddr and EvalVal are mutually recursive functions that 1193/// check if the expression in a return statement evaluates to an address 1194/// to a location on the stack. The recursion is used to traverse the 1195/// AST of the return expression, with recursion backtracking when we 1196/// encounter a subexpression that (1) clearly does not lead to the address 1197/// of a stack variable or (2) is something we cannot determine leads to 1198/// the address of a stack variable based on such local checking. 1199/// 1200/// EvalAddr processes expressions that are pointers that are used as 1201/// references (and not L-values). EvalVal handles all other values. 1202/// At the base case of the recursion is a check for a DeclRefExpr* in 1203/// the refers to a stack variable. 1204/// 1205/// This implementation handles: 1206/// 1207/// * pointer-to-pointer casts 1208/// * implicit conversions from array references to pointers 1209/// * taking the address of fields 1210/// * arbitrary interplay between "&" and "*" operators 1211/// * pointer arithmetic from an address of a stack variable 1212/// * taking the address of an array element where the array is on the stack 1213static DeclRefExpr* EvalAddr(Expr *E) { 1214 // We should only be called for evaluating pointer expressions. 1215 assert((E->getType()->isPointerType() || 1216 E->getType()->isBlockPointerType() || 1217 E->getType()->isObjCQualifiedIdType()) && 1218 "EvalAddr only works on pointers"); 1219 1220 // Our "symbolic interpreter" is just a dispatch off the currently 1221 // viewed AST node. We then recursively traverse the AST by calling 1222 // EvalAddr and EvalVal appropriately. 1223 switch (E->getStmtClass()) { 1224 case Stmt::ParenExprClass: 1225 // Ignore parentheses. 1226 return EvalAddr(cast<ParenExpr>(E)->getSubExpr()); 1227 1228 case Stmt::UnaryOperatorClass: { 1229 // The only unary operator that make sense to handle here 1230 // is AddrOf. All others don't make sense as pointers. 1231 UnaryOperator *U = cast<UnaryOperator>(E); 1232 1233 if (U->getOpcode() == UnaryOperator::AddrOf) 1234 return EvalVal(U->getSubExpr()); 1235 else 1236 return NULL; 1237 } 1238 1239 case Stmt::BinaryOperatorClass: { 1240 // Handle pointer arithmetic. All other binary operators are not valid 1241 // in this context. 1242 BinaryOperator *B = cast<BinaryOperator>(E); 1243 BinaryOperator::Opcode op = B->getOpcode(); 1244 1245 if (op != BinaryOperator::Add && op != BinaryOperator::Sub) 1246 return NULL; 1247 1248 Expr *Base = B->getLHS(); 1249 1250 // Determine which argument is the real pointer base. It could be 1251 // the RHS argument instead of the LHS. 1252 if (!Base->getType()->isPointerType()) Base = B->getRHS(); 1253 1254 assert (Base->getType()->isPointerType()); 1255 return EvalAddr(Base); 1256 } 1257 1258 // For conditional operators we need to see if either the LHS or RHS are 1259 // valid DeclRefExpr*s. If one of them is valid, we return it. 1260 case Stmt::ConditionalOperatorClass: { 1261 ConditionalOperator *C = cast<ConditionalOperator>(E); 1262 1263 // Handle the GNU extension for missing LHS. 1264 if (Expr *lhsExpr = C->getLHS()) 1265 if (DeclRefExpr* LHS = EvalAddr(lhsExpr)) 1266 return LHS; 1267 1268 return EvalAddr(C->getRHS()); 1269 } 1270 1271 // For casts, we need to handle conversions from arrays to 1272 // pointer values, and pointer-to-pointer conversions. 1273 case Stmt::ImplicitCastExprClass: 1274 case Stmt::CStyleCastExprClass: 1275 case Stmt::CXXFunctionalCastExprClass: { 1276 Expr* SubExpr = cast<CastExpr>(E)->getSubExpr(); 1277 QualType T = SubExpr->getType(); 1278 1279 if (SubExpr->getType()->isPointerType() || 1280 SubExpr->getType()->isBlockPointerType() || 1281 SubExpr->getType()->isObjCQualifiedIdType()) 1282 return EvalAddr(SubExpr); 1283 else if (T->isArrayType()) 1284 return EvalVal(SubExpr); 1285 else 1286 return 0; 1287 } 1288 1289 // C++ casts. For dynamic casts, static casts, and const casts, we 1290 // are always converting from a pointer-to-pointer, so we just blow 1291 // through the cast. In the case the dynamic cast doesn't fail (and 1292 // return NULL), we take the conservative route and report cases 1293 // where we return the address of a stack variable. For Reinterpre 1294 // FIXME: The comment about is wrong; we're not always converting 1295 // from pointer to pointer. I'm guessing that this code should also 1296 // handle references to objects. 1297 case Stmt::CXXStaticCastExprClass: 1298 case Stmt::CXXDynamicCastExprClass: 1299 case Stmt::CXXConstCastExprClass: 1300 case Stmt::CXXReinterpretCastExprClass: { 1301 Expr *S = cast<CXXNamedCastExpr>(E)->getSubExpr(); 1302 if (S->getType()->isPointerType() || S->getType()->isBlockPointerType()) 1303 return EvalAddr(S); 1304 else 1305 return NULL; 1306 } 1307 1308 // Everything else: we simply don't reason about them. 1309 default: 1310 return NULL; 1311 } 1312} 1313 1314 1315/// EvalVal - This function is complements EvalAddr in the mutual recursion. 1316/// See the comments for EvalAddr for more details. 1317static DeclRefExpr* EvalVal(Expr *E) { 1318 1319 // We should only be called for evaluating non-pointer expressions, or 1320 // expressions with a pointer type that are not used as references but instead 1321 // are l-values (e.g., DeclRefExpr with a pointer type). 1322 1323 // Our "symbolic interpreter" is just a dispatch off the currently 1324 // viewed AST node. We then recursively traverse the AST by calling 1325 // EvalAddr and EvalVal appropriately. 1326 switch (E->getStmtClass()) { 1327 case Stmt::DeclRefExprClass: 1328 case Stmt::QualifiedDeclRefExprClass: { 1329 // DeclRefExpr: the base case. When we hit a DeclRefExpr we are looking 1330 // at code that refers to a variable's name. We check if it has local 1331 // storage within the function, and if so, return the expression. 1332 DeclRefExpr *DR = cast<DeclRefExpr>(E); 1333 1334 if (VarDecl *V = dyn_cast<VarDecl>(DR->getDecl())) 1335 if(V->hasLocalStorage() && !V->getType()->isReferenceType()) return DR; 1336 1337 return NULL; 1338 } 1339 1340 case Stmt::ParenExprClass: 1341 // Ignore parentheses. 1342 return EvalVal(cast<ParenExpr>(E)->getSubExpr()); 1343 1344 case Stmt::UnaryOperatorClass: { 1345 // The only unary operator that make sense to handle here 1346 // is Deref. All others don't resolve to a "name." This includes 1347 // handling all sorts of rvalues passed to a unary operator. 1348 UnaryOperator *U = cast<UnaryOperator>(E); 1349 1350 if (U->getOpcode() == UnaryOperator::Deref) 1351 return EvalAddr(U->getSubExpr()); 1352 1353 return NULL; 1354 } 1355 1356 case Stmt::ArraySubscriptExprClass: { 1357 // Array subscripts are potential references to data on the stack. We 1358 // retrieve the DeclRefExpr* for the array variable if it indeed 1359 // has local storage. 1360 return EvalAddr(cast<ArraySubscriptExpr>(E)->getBase()); 1361 } 1362 1363 case Stmt::ConditionalOperatorClass: { 1364 // For conditional operators we need to see if either the LHS or RHS are 1365 // non-NULL DeclRefExpr's. If one is non-NULL, we return it. 1366 ConditionalOperator *C = cast<ConditionalOperator>(E); 1367 1368 // Handle the GNU extension for missing LHS. 1369 if (Expr *lhsExpr = C->getLHS()) 1370 if (DeclRefExpr *LHS = EvalVal(lhsExpr)) 1371 return LHS; 1372 1373 return EvalVal(C->getRHS()); 1374 } 1375 1376 // Accesses to members are potential references to data on the stack. 1377 case Stmt::MemberExprClass: { 1378 MemberExpr *M = cast<MemberExpr>(E); 1379 1380 // Check for indirect access. We only want direct field accesses. 1381 if (!M->isArrow()) 1382 return EvalVal(M->getBase()); 1383 else 1384 return NULL; 1385 } 1386 1387 // Everything else: we simply don't reason about them. 1388 default: 1389 return NULL; 1390 } 1391} 1392 1393//===--- CHECK: Floating-Point comparisons (-Wfloat-equal) ---------------===// 1394 1395/// Check for comparisons of floating point operands using != and ==. 1396/// Issue a warning if these are no self-comparisons, as they are not likely 1397/// to do what the programmer intended. 1398void Sema::CheckFloatComparison(SourceLocation loc, Expr* lex, Expr *rex) { 1399 bool EmitWarning = true; 1400 1401 Expr* LeftExprSansParen = lex->IgnoreParens(); 1402 Expr* RightExprSansParen = rex->IgnoreParens(); 1403 1404 // Special case: check for x == x (which is OK). 1405 // Do not emit warnings for such cases. 1406 if (DeclRefExpr* DRL = dyn_cast<DeclRefExpr>(LeftExprSansParen)) 1407 if (DeclRefExpr* DRR = dyn_cast<DeclRefExpr>(RightExprSansParen)) 1408 if (DRL->getDecl() == DRR->getDecl()) 1409 EmitWarning = false; 1410 1411 1412 // Special case: check for comparisons against literals that can be exactly 1413 // represented by APFloat. In such cases, do not emit a warning. This 1414 // is a heuristic: often comparison against such literals are used to 1415 // detect if a value in a variable has not changed. This clearly can 1416 // lead to false negatives. 1417 if (EmitWarning) { 1418 if (FloatingLiteral* FLL = dyn_cast<FloatingLiteral>(LeftExprSansParen)) { 1419 if (FLL->isExact()) 1420 EmitWarning = false; 1421 } 1422 else 1423 if (FloatingLiteral* FLR = dyn_cast<FloatingLiteral>(RightExprSansParen)){ 1424 if (FLR->isExact()) 1425 EmitWarning = false; 1426 } 1427 } 1428 1429 // Check for comparisons with builtin types. 1430 if (EmitWarning) 1431 if (CallExpr* CL = dyn_cast<CallExpr>(LeftExprSansParen)) 1432 if (CL->isBuiltinCall(Context)) 1433 EmitWarning = false; 1434 1435 if (EmitWarning) 1436 if (CallExpr* CR = dyn_cast<CallExpr>(RightExprSansParen)) 1437 if (CR->isBuiltinCall(Context)) 1438 EmitWarning = false; 1439 1440 // Emit the diagnostic. 1441 if (EmitWarning) 1442 Diag(loc, diag::warn_floatingpoint_eq) 1443 << lex->getSourceRange() << rex->getSourceRange(); 1444} 1445