| //===--- SemaChecking.cpp - Extra Semantic Checking -----------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements extra semantic analysis beyond what is enforced |
| // by the C type system. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "Sema.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/DeclObjC.h" |
| #include "clang/AST/ExprCXX.h" |
| #include "clang/AST/ExprObjC.h" |
| #include "clang/Lex/LiteralSupport.h" |
| #include "clang/Lex/Preprocessor.h" |
| using namespace clang; |
| |
| /// getLocationOfStringLiteralByte - Return a source location that points to the |
| /// specified byte of the specified string literal. |
| /// |
| /// Strings are amazingly complex. They can be formed from multiple tokens and |
| /// can have escape sequences in them in addition to the usual trigraph and |
| /// escaped newline business. This routine handles this complexity. |
| /// |
| SourceLocation Sema::getLocationOfStringLiteralByte(const StringLiteral *SL, |
| unsigned ByteNo) const { |
| assert(!SL->isWide() && "This doesn't work for wide strings yet"); |
| |
| // Loop over all of the tokens in this string until we find the one that |
| // contains the byte we're looking for. |
| unsigned TokNo = 0; |
| while (1) { |
| assert(TokNo < SL->getNumConcatenated() && "Invalid byte number!"); |
| SourceLocation StrTokLoc = SL->getStrTokenLoc(TokNo); |
| |
| // Get the spelling of the string so that we can get the data that makes up |
| // the string literal, not the identifier for the macro it is potentially |
| // expanded through. |
| SourceLocation StrTokSpellingLoc = SourceMgr.getSpellingLoc(StrTokLoc); |
| |
| // Re-lex the token to get its length and original spelling. |
| std::pair<FileID, unsigned> LocInfo = |
| SourceMgr.getDecomposedLoc(StrTokSpellingLoc); |
| std::pair<const char *,const char *> Buffer = |
| SourceMgr.getBufferData(LocInfo.first); |
| const char *StrData = Buffer.first+LocInfo.second; |
| |
| // Create a langops struct and enable trigraphs. This is sufficient for |
| // relexing tokens. |
| LangOptions LangOpts; |
| LangOpts.Trigraphs = true; |
| |
| // Create a lexer starting at the beginning of this token. |
| Lexer TheLexer(StrTokSpellingLoc, LangOpts, Buffer.first, StrData, |
| Buffer.second); |
| Token TheTok; |
| TheLexer.LexFromRawLexer(TheTok); |
| |
| // Use the StringLiteralParser to compute the length of the string in bytes. |
| StringLiteralParser SLP(&TheTok, 1, PP); |
| unsigned TokNumBytes = SLP.GetStringLength(); |
| |
| // If the byte is in this token, return the location of the byte. |
| if (ByteNo < TokNumBytes || |
| (ByteNo == TokNumBytes && TokNo == SL->getNumConcatenated())) { |
| unsigned Offset = |
| StringLiteralParser::getOffsetOfStringByte(TheTok, ByteNo, PP); |
| |
| // Now that we know the offset of the token in the spelling, use the |
| // preprocessor to get the offset in the original source. |
| return PP.AdvanceToTokenCharacter(StrTokLoc, Offset); |
| } |
| |
| // Move to the next string token. |
| ++TokNo; |
| ByteNo -= TokNumBytes; |
| } |
| } |
| |
| |
| /// CheckFunctionCall - Check a direct function call for various correctness |
| /// and safety properties not strictly enforced by the C type system. |
| Action::OwningExprResult |
| Sema::CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall) { |
| OwningExprResult TheCallResult(Owned(TheCall)); |
| // Get the IdentifierInfo* for the called function. |
| IdentifierInfo *FnInfo = FDecl->getIdentifier(); |
| |
| // None of the checks below are needed for functions that don't have |
| // simple names (e.g., C++ conversion functions). |
| if (!FnInfo) |
| return move(TheCallResult); |
| |
| switch (FDecl->getBuiltinID(Context)) { |
| case Builtin::BI__builtin___CFStringMakeConstantString: |
| assert(TheCall->getNumArgs() == 1 && |
| "Wrong # arguments to builtin CFStringMakeConstantString"); |
| if (CheckObjCString(TheCall->getArg(0))) |
| return ExprError(); |
| return move(TheCallResult); |
| case Builtin::BI__builtin_stdarg_start: |
| case Builtin::BI__builtin_va_start: |
| if (SemaBuiltinVAStart(TheCall)) |
| return ExprError(); |
| return move(TheCallResult); |
| case Builtin::BI__builtin_isgreater: |
| case Builtin::BI__builtin_isgreaterequal: |
| case Builtin::BI__builtin_isless: |
| case Builtin::BI__builtin_islessequal: |
| case Builtin::BI__builtin_islessgreater: |
| case Builtin::BI__builtin_isunordered: |
| if (SemaBuiltinUnorderedCompare(TheCall)) |
| return ExprError(); |
| return move(TheCallResult); |
| case Builtin::BI__builtin_return_address: |
| case Builtin::BI__builtin_frame_address: |
| if (SemaBuiltinStackAddress(TheCall)) |
| return ExprError(); |
| return move(TheCallResult); |
| case Builtin::BI__builtin_shufflevector: |
| return SemaBuiltinShuffleVector(TheCall); |
| // TheCall will be freed by the smart pointer here, but that's fine, since |
| // SemaBuiltinShuffleVector guts it, but then doesn't release it. |
| case Builtin::BI__builtin_prefetch: |
| if (SemaBuiltinPrefetch(TheCall)) |
| return ExprError(); |
| return move(TheCallResult); |
| case Builtin::BI__builtin_object_size: |
| if (SemaBuiltinObjectSize(TheCall)) |
| return ExprError(); |
| } |
| |
| // FIXME: This mechanism should be abstracted to be less fragile and |
| // more efficient. For example, just map function ids to custom |
| // handlers. |
| |
| // Printf checking. |
| if (const FormatAttr *Format = FDecl->getAttr<FormatAttr>()) { |
| if (Format->getType() == "printf") { |
| bool HasVAListArg = Format->getFirstArg() == 0; |
| if (!HasVAListArg) { |
| if (const FunctionProtoType *Proto |
| = FDecl->getType()->getAsFunctionProtoType()) |
| HasVAListArg = !Proto->isVariadic(); |
| } |
| CheckPrintfArguments(TheCall, HasVAListArg, Format->getFormatIdx() - 1, |
| HasVAListArg ? 0 : Format->getFirstArg() - 1); |
| } |
| } |
| |
| return move(TheCallResult); |
| } |
| |
| /// CheckObjCString - Checks that the argument to the builtin |
| /// CFString constructor is correct |
| /// FIXME: GCC currently emits the following warning: |
| /// "warning: input conversion stopped due to an input byte that does not |
| /// belong to the input codeset UTF-8" |
| /// Note: It might also make sense to do the UTF-16 conversion here (would |
| /// simplify the backend). |
| bool Sema::CheckObjCString(Expr *Arg) { |
| Arg = Arg->IgnoreParenCasts(); |
| StringLiteral *Literal = dyn_cast<StringLiteral>(Arg); |
| |
| if (!Literal || Literal->isWide()) { |
| Diag(Arg->getLocStart(), diag::err_cfstring_literal_not_string_constant) |
| << Arg->getSourceRange(); |
| return true; |
| } |
| |
| const char *Data = Literal->getStrData(); |
| unsigned Length = Literal->getByteLength(); |
| |
| for (unsigned i = 0; i < Length; ++i) { |
| if (!Data[i]) { |
| Diag(getLocationOfStringLiteralByte(Literal, i), |
| diag::warn_cfstring_literal_contains_nul_character) |
| << Arg->getSourceRange(); |
| break; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// SemaBuiltinVAStart - Check the arguments to __builtin_va_start for validity. |
| /// Emit an error and return true on failure, return false on success. |
| bool Sema::SemaBuiltinVAStart(CallExpr *TheCall) { |
| Expr *Fn = TheCall->getCallee(); |
| if (TheCall->getNumArgs() > 2) { |
| Diag(TheCall->getArg(2)->getLocStart(), |
| diag::err_typecheck_call_too_many_args) |
| << 0 /*function call*/ << Fn->getSourceRange() |
| << SourceRange(TheCall->getArg(2)->getLocStart(), |
| (*(TheCall->arg_end()-1))->getLocEnd()); |
| return true; |
| } |
| |
| if (TheCall->getNumArgs() < 2) { |
| return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) |
| << 0 /*function call*/; |
| } |
| |
| // Determine whether the current function is variadic or not. |
| bool isVariadic; |
| if (CurBlock) |
| isVariadic = CurBlock->isVariadic; |
| else if (getCurFunctionDecl()) { |
| if (FunctionProtoType* FTP = |
| dyn_cast<FunctionProtoType>(getCurFunctionDecl()->getType())) |
| isVariadic = FTP->isVariadic(); |
| else |
| isVariadic = false; |
| } else { |
| isVariadic = getCurMethodDecl()->isVariadic(); |
| } |
| |
| if (!isVariadic) { |
| Diag(Fn->getLocStart(), diag::err_va_start_used_in_non_variadic_function); |
| return true; |
| } |
| |
| // Verify that the second argument to the builtin is the last argument of the |
| // current function or method. |
| bool SecondArgIsLastNamedArgument = false; |
| const Expr *Arg = TheCall->getArg(1)->IgnoreParenCasts(); |
| |
| if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Arg)) { |
| if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(DR->getDecl())) { |
| // FIXME: This isn't correct for methods (results in bogus warning). |
| // Get the last formal in the current function. |
| const ParmVarDecl *LastArg; |
| if (CurBlock) |
| LastArg = *(CurBlock->TheDecl->param_end()-1); |
| else if (FunctionDecl *FD = getCurFunctionDecl()) |
| LastArg = *(FD->param_end()-1); |
| else |
| LastArg = *(getCurMethodDecl()->param_end()-1); |
| SecondArgIsLastNamedArgument = PV == LastArg; |
| } |
| } |
| |
| if (!SecondArgIsLastNamedArgument) |
| Diag(TheCall->getArg(1)->getLocStart(), |
| diag::warn_second_parameter_of_va_start_not_last_named_argument); |
| return false; |
| } |
| |
| /// SemaBuiltinUnorderedCompare - Handle functions like __builtin_isgreater and |
| /// friends. This is declared to take (...), so we have to check everything. |
| bool Sema::SemaBuiltinUnorderedCompare(CallExpr *TheCall) { |
| if (TheCall->getNumArgs() < 2) |
| return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args) |
| << 0 /*function call*/; |
| if (TheCall->getNumArgs() > 2) |
| return Diag(TheCall->getArg(2)->getLocStart(), |
| diag::err_typecheck_call_too_many_args) |
| << 0 /*function call*/ |
| << SourceRange(TheCall->getArg(2)->getLocStart(), |
| (*(TheCall->arg_end()-1))->getLocEnd()); |
| |
| Expr *OrigArg0 = TheCall->getArg(0); |
| Expr *OrigArg1 = TheCall->getArg(1); |
| |
| // Do standard promotions between the two arguments, returning their common |
| // type. |
| QualType Res = UsualArithmeticConversions(OrigArg0, OrigArg1, false); |
| |
| // Make sure any conversions are pushed back into the call; this is |
| // type safe since unordered compare builtins are declared as "_Bool |
| // foo(...)". |
| TheCall->setArg(0, OrigArg0); |
| TheCall->setArg(1, OrigArg1); |
| |
| // If the common type isn't a real floating type, then the arguments were |
| // invalid for this operation. |
| if (!Res->isRealFloatingType()) |
| return Diag(OrigArg0->getLocStart(), |
| diag::err_typecheck_call_invalid_ordered_compare) |
| << OrigArg0->getType() << OrigArg1->getType() |
| << SourceRange(OrigArg0->getLocStart(), OrigArg1->getLocEnd()); |
| |
| return false; |
| } |
| |
| bool Sema::SemaBuiltinStackAddress(CallExpr *TheCall) { |
| // The signature for these builtins is exact; the only thing we need |
| // to check is that the argument is a constant. |
| SourceLocation Loc; |
| if (!TheCall->getArg(0)->isIntegerConstantExpr(Context, &Loc)) |
| return Diag(Loc, diag::err_stack_const_level) << TheCall->getSourceRange(); |
| |
| return false; |
| } |
| |
| /// SemaBuiltinShuffleVector - Handle __builtin_shufflevector. |
| // This is declared to take (...), so we have to check everything. |
| Action::OwningExprResult Sema::SemaBuiltinShuffleVector(CallExpr *TheCall) { |
| if (TheCall->getNumArgs() < 3) |
| return ExprError(Diag(TheCall->getLocEnd(), |
| diag::err_typecheck_call_too_few_args) |
| << 0 /*function call*/ << TheCall->getSourceRange()); |
| |
| QualType FAType = TheCall->getArg(0)->getType(); |
| QualType SAType = TheCall->getArg(1)->getType(); |
| |
| if (!FAType->isVectorType() || !SAType->isVectorType()) { |
| Diag(TheCall->getLocStart(), diag::err_shufflevector_non_vector) |
| << SourceRange(TheCall->getArg(0)->getLocStart(), |
| TheCall->getArg(1)->getLocEnd()); |
| return ExprError(); |
| } |
| |
| if (Context.getCanonicalType(FAType).getUnqualifiedType() != |
| Context.getCanonicalType(SAType).getUnqualifiedType()) { |
| Diag(TheCall->getLocStart(), diag::err_shufflevector_incompatible_vector) |
| << SourceRange(TheCall->getArg(0)->getLocStart(), |
| TheCall->getArg(1)->getLocEnd()); |
| return ExprError(); |
| } |
| |
| unsigned numElements = FAType->getAsVectorType()->getNumElements(); |
| if (TheCall->getNumArgs() != numElements+2) { |
| if (TheCall->getNumArgs() < numElements+2) |
| return ExprError(Diag(TheCall->getLocEnd(), |
| diag::err_typecheck_call_too_few_args) |
| << 0 /*function call*/ << TheCall->getSourceRange()); |
| return ExprError(Diag(TheCall->getLocEnd(), |
| diag::err_typecheck_call_too_many_args) |
| << 0 /*function call*/ << TheCall->getSourceRange()); |
| } |
| |
| for (unsigned i = 2; i < TheCall->getNumArgs(); i++) { |
| llvm::APSInt Result(32); |
| if (!TheCall->getArg(i)->isIntegerConstantExpr(Result, Context)) |
| return ExprError(Diag(TheCall->getLocStart(), |
| diag::err_shufflevector_nonconstant_argument) |
| << TheCall->getArg(i)->getSourceRange()); |
| |
| if (Result.getActiveBits() > 64 || Result.getZExtValue() >= numElements*2) |
| return ExprError(Diag(TheCall->getLocStart(), |
| diag::err_shufflevector_argument_too_large) |
| << TheCall->getArg(i)->getSourceRange()); |
| } |
| |
| llvm::SmallVector<Expr*, 32> exprs; |
| |
| for (unsigned i = 0, e = TheCall->getNumArgs(); i != e; i++) { |
| exprs.push_back(TheCall->getArg(i)); |
| TheCall->setArg(i, 0); |
| } |
| |
| return Owned(new (Context) ShuffleVectorExpr(exprs.begin(), numElements+2, |
| FAType, |
| TheCall->getCallee()->getLocStart(), |
| TheCall->getRParenLoc())); |
| } |
| |
| /// SemaBuiltinPrefetch - Handle __builtin_prefetch. |
| // This is declared to take (const void*, ...) and can take two |
| // optional constant int args. |
| bool Sema::SemaBuiltinPrefetch(CallExpr *TheCall) { |
| unsigned NumArgs = TheCall->getNumArgs(); |
| |
| if (NumArgs > 3) |
| return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_many_args) |
| << 0 /*function call*/ << TheCall->getSourceRange(); |
| |
| // Argument 0 is checked for us and the remaining arguments must be |
| // constant integers. |
| for (unsigned i = 1; i != NumArgs; ++i) { |
| Expr *Arg = TheCall->getArg(i); |
| QualType RWType = Arg->getType(); |
| |
| const BuiltinType *BT = RWType->getAsBuiltinType(); |
| llvm::APSInt Result; |
| if (!BT || BT->getKind() != BuiltinType::Int || |
| !Arg->isIntegerConstantExpr(Result, Context)) |
| return Diag(TheCall->getLocStart(), diag::err_prefetch_invalid_argument) |
| << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); |
| |
| // FIXME: gcc issues a warning and rewrites these to 0. These |
| // seems especially odd for the third argument since the default |
| // is 3. |
| if (i == 1) { |
| if (Result.getSExtValue() < 0 || Result.getSExtValue() > 1) |
| return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) |
| << "0" << "1" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); |
| } else { |
| if (Result.getSExtValue() < 0 || Result.getSExtValue() > 3) |
| return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) |
| << "0" << "3" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); |
| } |
| } |
| |
| return false; |
| } |
| |
| /// SemaBuiltinObjectSize - Handle __builtin_object_size(void *ptr, |
| /// int type). This simply type checks that type is one of the defined |
| /// constants (0-3). |
| bool Sema::SemaBuiltinObjectSize(CallExpr *TheCall) { |
| Expr *Arg = TheCall->getArg(1); |
| QualType ArgType = Arg->getType(); |
| const BuiltinType *BT = ArgType->getAsBuiltinType(); |
| llvm::APSInt Result(32); |
| if (!BT || BT->getKind() != BuiltinType::Int || |
| !Arg->isIntegerConstantExpr(Result, Context)) { |
| return Diag(TheCall->getLocStart(), diag::err_object_size_invalid_argument) |
| << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); |
| } |
| |
| if (Result.getSExtValue() < 0 || Result.getSExtValue() > 3) { |
| return Diag(TheCall->getLocStart(), diag::err_argument_invalid_range) |
| << "0" << "3" << SourceRange(Arg->getLocStart(), Arg->getLocEnd()); |
| } |
| |
| return false; |
| } |
| |
| // Handle i > 1 ? "x" : "y", recursivelly |
| bool Sema::SemaCheckStringLiteral(const Expr *E, const CallExpr *TheCall, |
| bool HasVAListArg, |
| unsigned format_idx, unsigned firstDataArg) { |
| |
| switch (E->getStmtClass()) { |
| case Stmt::ConditionalOperatorClass: { |
| const ConditionalOperator *C = cast<ConditionalOperator>(E); |
| return SemaCheckStringLiteral(C->getLHS(), TheCall, |
| HasVAListArg, format_idx, firstDataArg) |
| && SemaCheckStringLiteral(C->getRHS(), TheCall, |
| HasVAListArg, format_idx, firstDataArg); |
| } |
| |
| case Stmt::ImplicitCastExprClass: { |
| const ImplicitCastExpr *Expr = cast<ImplicitCastExpr>(E); |
| return SemaCheckStringLiteral(Expr->getSubExpr(), TheCall, HasVAListArg, |
| format_idx, firstDataArg); |
| } |
| |
| case Stmt::ParenExprClass: { |
| const ParenExpr *Expr = cast<ParenExpr>(E); |
| return SemaCheckStringLiteral(Expr->getSubExpr(), TheCall, HasVAListArg, |
| format_idx, firstDataArg); |
| } |
| |
| case Stmt::DeclRefExprClass: { |
| const DeclRefExpr *DR = cast<DeclRefExpr>(E); |
| |
| // As an exception, do not flag errors for variables binding to |
| // const string literals. |
| if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) { |
| bool isConstant = false; |
| QualType T = DR->getType(); |
| |
| if (const ArrayType *AT = Context.getAsArrayType(T)) { |
| isConstant = AT->getElementType().isConstant(Context); |
| } |
| else if (const PointerType *PT = T->getAsPointerType()) { |
| isConstant = T.isConstant(Context) && |
| PT->getPointeeType().isConstant(Context); |
| } |
| |
| if (isConstant) { |
| const VarDecl *Def = 0; |
| if (const Expr *Init = VD->getDefinition(Def)) |
| return SemaCheckStringLiteral(Init, TheCall, |
| HasVAListArg, format_idx, firstDataArg); |
| } |
| } |
| |
| return false; |
| } |
| |
| case Stmt::ObjCStringLiteralClass: |
| case Stmt::StringLiteralClass: { |
| const StringLiteral *StrE = NULL; |
| |
| if (const ObjCStringLiteral *ObjCFExpr = dyn_cast<ObjCStringLiteral>(E)) |
| StrE = ObjCFExpr->getString(); |
| else |
| StrE = cast<StringLiteral>(E); |
| |
| if (StrE) { |
| CheckPrintfString(StrE, E, TheCall, HasVAListArg, format_idx, |
| firstDataArg); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| default: |
| return false; |
| } |
| } |
| |
| |
| /// CheckPrintfArguments - Check calls to printf (and similar functions) for |
| /// correct use of format strings. |
| /// |
| /// HasVAListArg - A predicate indicating whether the printf-like |
| /// function is passed an explicit va_arg argument (e.g., vprintf) |
| /// |
| /// format_idx - The index into Args for the format string. |
| /// |
| /// Improper format strings to functions in the printf family can be |
| /// the source of bizarre bugs and very serious security holes. A |
| /// good source of information is available in the following paper |
| /// (which includes additional references): |
| /// |
| /// FormatGuard: Automatic Protection From printf Format String |
| /// Vulnerabilities, Proceedings of the 10th USENIX Security Symposium, 2001. |
| /// |
| /// Functionality implemented: |
| /// |
| /// We can statically check the following properties for string |
| /// literal format strings for non v.*printf functions (where the |
| /// arguments are passed directly): |
| // |
| /// (1) Are the number of format conversions equal to the number of |
| /// data arguments? |
| /// |
| /// (2) Does each format conversion correctly match the type of the |
| /// corresponding data argument? (TODO) |
| /// |
| /// Moreover, for all printf functions we can: |
| /// |
| /// (3) Check for a missing format string (when not caught by type checking). |
| /// |
| /// (4) Check for no-operation flags; e.g. using "#" with format |
| /// conversion 'c' (TODO) |
| /// |
| /// (5) Check the use of '%n', a major source of security holes. |
| /// |
| /// (6) Check for malformed format conversions that don't specify anything. |
| /// |
| /// (7) Check for empty format strings. e.g: printf(""); |
| /// |
| /// (8) Check that the format string is a wide literal. |
| /// |
| /// (9) Also check the arguments of functions with the __format__ attribute. |
| /// (TODO). |
| /// |
| /// All of these checks can be done by parsing the format string. |
| /// |
| /// For now, we ONLY do (1), (3), (5), (6), (7), and (8). |
| void |
| Sema::CheckPrintfArguments(const CallExpr *TheCall, bool HasVAListArg, |
| unsigned format_idx, unsigned firstDataArg) { |
| const Expr *Fn = TheCall->getCallee(); |
| |
| // CHECK: printf-like function is called with no format string. |
| if (format_idx >= TheCall->getNumArgs()) { |
| Diag(TheCall->getRParenLoc(), diag::warn_printf_missing_format_string) |
| << Fn->getSourceRange(); |
| return; |
| } |
| |
| const Expr *OrigFormatExpr = TheCall->getArg(format_idx)->IgnoreParenCasts(); |
| |
| // CHECK: format string is not a string literal. |
| // |
| // Dynamically generated format strings are difficult to |
| // automatically vet at compile time. Requiring that format strings |
| // are string literals: (1) permits the checking of format strings by |
| // the compiler and thereby (2) can practically remove the source of |
| // many format string exploits. |
| |
| // Format string can be either ObjC string (e.g. @"%d") or |
| // C string (e.g. "%d") |
| // ObjC string uses the same format specifiers as C string, so we can use |
| // the same format string checking logic for both ObjC and C strings. |
| bool isFExpr = SemaCheckStringLiteral(OrigFormatExpr, TheCall, |
| HasVAListArg, format_idx, |
| firstDataArg); |
| |
| if (!isFExpr) { |
| // For vprintf* functions (i.e., HasVAListArg==true), we add a |
| // special check to see if the format string is a function parameter |
| // of the function calling the printf function. If the function |
| // has an attribute indicating it is a printf-like function, then we |
| // should suppress warnings concerning non-literals being used in a call |
| // to a vprintf function. For example: |
| // |
| // void |
| // logmessage(char const *fmt __attribute__ (format (printf, 1, 2)), ...) { |
| // va_list ap; |
| // va_start(ap, fmt); |
| // vprintf(fmt, ap); // Do NOT emit a warning about "fmt". |
| // ... |
| // |
| // |
| // FIXME: We don't have full attribute support yet, so just check to see |
| // if the argument is a DeclRefExpr that references a parameter. We'll |
| // add proper support for checking the attribute later. |
| if (HasVAListArg) |
| if (const DeclRefExpr* DR = dyn_cast<DeclRefExpr>(OrigFormatExpr)) |
| if (isa<ParmVarDecl>(DR->getDecl())) |
| return; |
| |
| Diag(TheCall->getArg(format_idx)->getLocStart(), |
| diag::warn_printf_not_string_constant) |
| << OrigFormatExpr->getSourceRange(); |
| return; |
| } |
| } |
| |
| void Sema::CheckPrintfString(const StringLiteral *FExpr, |
| const Expr *OrigFormatExpr, |
| const CallExpr *TheCall, bool HasVAListArg, |
| unsigned format_idx, unsigned firstDataArg) { |
| |
| const ObjCStringLiteral *ObjCFExpr = |
| dyn_cast<ObjCStringLiteral>(OrigFormatExpr); |
| |
| // CHECK: is the format string a wide literal? |
| if (FExpr->isWide()) { |
| Diag(FExpr->getLocStart(), |
| diag::warn_printf_format_string_is_wide_literal) |
| << OrigFormatExpr->getSourceRange(); |
| return; |
| } |
| |
| // Str - The format string. NOTE: this is NOT null-terminated! |
| const char * const Str = FExpr->getStrData(); |
| |
| // CHECK: empty format string? |
| const unsigned StrLen = FExpr->getByteLength(); |
| |
| if (StrLen == 0) { |
| Diag(FExpr->getLocStart(), diag::warn_printf_empty_format_string) |
| << OrigFormatExpr->getSourceRange(); |
| return; |
| } |
| |
| // We process the format string using a binary state machine. The |
| // current state is stored in CurrentState. |
| enum { |
| state_OrdChr, |
| state_Conversion |
| } CurrentState = state_OrdChr; |
| |
| // numConversions - The number of conversions seen so far. This is |
| // incremented as we traverse the format string. |
| unsigned numConversions = 0; |
| |
| // numDataArgs - The number of data arguments after the format |
| // string. This can only be determined for non vprintf-like |
| // functions. For those functions, this value is 1 (the sole |
| // va_arg argument). |
| unsigned numDataArgs = TheCall->getNumArgs()-firstDataArg; |
| |
| // Inspect the format string. |
| unsigned StrIdx = 0; |
| |
| // LastConversionIdx - Index within the format string where we last saw |
| // a '%' character that starts a new format conversion. |
| unsigned LastConversionIdx = 0; |
| |
| for (; StrIdx < StrLen; ++StrIdx) { |
| |
| // Is the number of detected conversion conversions greater than |
| // the number of matching data arguments? If so, stop. |
| if (!HasVAListArg && numConversions > numDataArgs) break; |
| |
| // Handle "\0" |
| if (Str[StrIdx] == '\0') { |
| // The string returned by getStrData() is not null-terminated, |
| // so the presence of a null character is likely an error. |
| Diag(getLocationOfStringLiteralByte(FExpr, StrIdx), |
| diag::warn_printf_format_string_contains_null_char) |
| << OrigFormatExpr->getSourceRange(); |
| return; |
| } |
| |
| // Ordinary characters (not processing a format conversion). |
| if (CurrentState == state_OrdChr) { |
| if (Str[StrIdx] == '%') { |
| CurrentState = state_Conversion; |
| LastConversionIdx = StrIdx; |
| } |
| continue; |
| } |
| |
| // Seen '%'. Now processing a format conversion. |
| switch (Str[StrIdx]) { |
| // Handle dynamic precision or width specifier. |
| case '*': { |
| ++numConversions; |
| |
| if (!HasVAListArg && numConversions > numDataArgs) { |
| SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, StrIdx); |
| |
| if (Str[StrIdx-1] == '.') |
| Diag(Loc, diag::warn_printf_asterisk_precision_missing_arg) |
| << OrigFormatExpr->getSourceRange(); |
| else |
| Diag(Loc, diag::warn_printf_asterisk_width_missing_arg) |
| << OrigFormatExpr->getSourceRange(); |
| |
| // Don't do any more checking. We'll just emit spurious errors. |
| return; |
| } |
| |
| // Perform type checking on width/precision specifier. |
| const Expr *E = TheCall->getArg(format_idx+numConversions); |
| if (const BuiltinType *BT = E->getType()->getAsBuiltinType()) |
| if (BT->getKind() == BuiltinType::Int) |
| break; |
| |
| SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, StrIdx); |
| |
| if (Str[StrIdx-1] == '.') |
| Diag(Loc, diag::warn_printf_asterisk_precision_wrong_type) |
| << E->getType() << E->getSourceRange(); |
| else |
| Diag(Loc, diag::warn_printf_asterisk_width_wrong_type) |
| << E->getType() << E->getSourceRange(); |
| |
| break; |
| } |
| |
| // Characters which can terminate a format conversion |
| // (e.g. "%d"). Characters that specify length modifiers or |
| // other flags are handled by the default case below. |
| // |
| // FIXME: additional checks will go into the following cases. |
| case 'i': |
| case 'd': |
| case 'o': |
| case 'u': |
| case 'x': |
| case 'X': |
| case 'D': |
| case 'O': |
| case 'U': |
| case 'e': |
| case 'E': |
| case 'f': |
| case 'F': |
| case 'g': |
| case 'G': |
| case 'a': |
| case 'A': |
| case 'c': |
| case 'C': |
| case 'S': |
| case 's': |
| case 'p': |
| ++numConversions; |
| CurrentState = state_OrdChr; |
| break; |
| |
| // CHECK: Are we using "%n"? Issue a warning. |
| case 'n': { |
| ++numConversions; |
| CurrentState = state_OrdChr; |
| SourceLocation Loc = getLocationOfStringLiteralByte(FExpr, |
| LastConversionIdx); |
| |
| Diag(Loc, diag::warn_printf_write_back)<<OrigFormatExpr->getSourceRange(); |
| break; |
| } |
| |
| // Handle "%@" |
| case '@': |
| // %@ is allowed in ObjC format strings only. |
| if(ObjCFExpr != NULL) |
| CurrentState = state_OrdChr; |
| else { |
| // Issue a warning: invalid format conversion. |
| SourceLocation Loc = |
| getLocationOfStringLiteralByte(FExpr, LastConversionIdx); |
| |
| Diag(Loc, diag::warn_printf_invalid_conversion) |
| << std::string(Str+LastConversionIdx, |
| Str+std::min(LastConversionIdx+2, StrLen)) |
| << OrigFormatExpr->getSourceRange(); |
| } |
| ++numConversions; |
| break; |
| |
| // Handle "%%" |
| case '%': |
| // Sanity check: Was the first "%" character the previous one? |
| // If not, we will assume that we have a malformed format |
| // conversion, and that the current "%" character is the start |
| // of a new conversion. |
| if (StrIdx - LastConversionIdx == 1) |
| CurrentState = state_OrdChr; |
| else { |
| // Issue a warning: invalid format conversion. |
| SourceLocation Loc = |
| getLocationOfStringLiteralByte(FExpr, LastConversionIdx); |
| |
| Diag(Loc, diag::warn_printf_invalid_conversion) |
| << std::string(Str+LastConversionIdx, Str+StrIdx) |
| << OrigFormatExpr->getSourceRange(); |
| |
| // This conversion is broken. Advance to the next format |
| // conversion. |
| LastConversionIdx = StrIdx; |
| ++numConversions; |
| } |
| break; |
| |
| default: |
| // This case catches all other characters: flags, widths, etc. |
| // We should eventually process those as well. |
| break; |
| } |
| } |
| |
| if (CurrentState == state_Conversion) { |
| // Issue a warning: invalid format conversion. |
| SourceLocation Loc = |
| getLocationOfStringLiteralByte(FExpr, LastConversionIdx); |
| |
| Diag(Loc, diag::warn_printf_invalid_conversion) |
| << std::string(Str+LastConversionIdx, |
| Str+std::min(LastConversionIdx+2, StrLen)) |
| << OrigFormatExpr->getSourceRange(); |
| return; |
| } |
| |
| if (!HasVAListArg) { |
| // CHECK: Does the number of format conversions exceed the number |
| // of data arguments? |
| if (numConversions > numDataArgs) { |
| SourceLocation Loc = |
| getLocationOfStringLiteralByte(FExpr, LastConversionIdx); |
| |
| Diag(Loc, diag::warn_printf_insufficient_data_args) |
| << OrigFormatExpr->getSourceRange(); |
| } |
| // CHECK: Does the number of data arguments exceed the number of |
| // format conversions in the format string? |
| else if (numConversions < numDataArgs) |
| Diag(TheCall->getArg(format_idx+numConversions+1)->getLocStart(), |
| diag::warn_printf_too_many_data_args) |
| << OrigFormatExpr->getSourceRange(); |
| } |
| } |
| |
| //===--- CHECK: Return Address of Stack Variable --------------------------===// |
| |
| static DeclRefExpr* EvalVal(Expr *E); |
| static DeclRefExpr* EvalAddr(Expr* E); |
| |
| /// CheckReturnStackAddr - Check if a return statement returns the address |
| /// of a stack variable. |
| void |
| Sema::CheckReturnStackAddr(Expr *RetValExp, QualType lhsType, |
| SourceLocation ReturnLoc) { |
| |
| // Perform checking for returned stack addresses. |
| if (lhsType->isPointerType() || lhsType->isBlockPointerType()) { |
| if (DeclRefExpr *DR = EvalAddr(RetValExp)) |
| Diag(DR->getLocStart(), diag::warn_ret_stack_addr) |
| << DR->getDecl()->getDeclName() << RetValExp->getSourceRange(); |
| |
| // Skip over implicit cast expressions when checking for block expressions. |
| if (ImplicitCastExpr *IcExpr = |
| dyn_cast_or_null<ImplicitCastExpr>(RetValExp)) |
| RetValExp = IcExpr->getSubExpr(); |
| |
| if (BlockExpr *C = dyn_cast_or_null<BlockExpr>(RetValExp)) |
| if (C->hasBlockDeclRefExprs()) |
| Diag(C->getLocStart(), diag::err_ret_local_block) |
| << C->getSourceRange(); |
| } |
| // Perform checking for stack values returned by reference. |
| else if (lhsType->isReferenceType()) { |
| // Check for a reference to the stack |
| if (DeclRefExpr *DR = EvalVal(RetValExp)) |
| Diag(DR->getLocStart(), diag::warn_ret_stack_ref) |
| << DR->getDecl()->getDeclName() << RetValExp->getSourceRange(); |
| } |
| } |
| |
| /// EvalAddr - EvalAddr and EvalVal are mutually recursive functions that |
| /// check if the expression in a return statement evaluates to an address |
| /// to a location on the stack. The recursion is used to traverse the |
| /// AST of the return expression, with recursion backtracking when we |
| /// encounter a subexpression that (1) clearly does not lead to the address |
| /// of a stack variable or (2) is something we cannot determine leads to |
| /// the address of a stack variable based on such local checking. |
| /// |
| /// EvalAddr processes expressions that are pointers that are used as |
| /// references (and not L-values). EvalVal handles all other values. |
| /// At the base case of the recursion is a check for a DeclRefExpr* in |
| /// the refers to a stack variable. |
| /// |
| /// This implementation handles: |
| /// |
| /// * pointer-to-pointer casts |
| /// * implicit conversions from array references to pointers |
| /// * taking the address of fields |
| /// * arbitrary interplay between "&" and "*" operators |
| /// * pointer arithmetic from an address of a stack variable |
| /// * taking the address of an array element where the array is on the stack |
| static DeclRefExpr* EvalAddr(Expr *E) { |
| // We should only be called for evaluating pointer expressions. |
| assert((E->getType()->isPointerType() || |
| E->getType()->isBlockPointerType() || |
| E->getType()->isObjCQualifiedIdType()) && |
| "EvalAddr only works on pointers"); |
| |
| // Our "symbolic interpreter" is just a dispatch off the currently |
| // viewed AST node. We then recursively traverse the AST by calling |
| // EvalAddr and EvalVal appropriately. |
| switch (E->getStmtClass()) { |
| case Stmt::ParenExprClass: |
| // Ignore parentheses. |
| return EvalAddr(cast<ParenExpr>(E)->getSubExpr()); |
| |
| case Stmt::UnaryOperatorClass: { |
| // The only unary operator that make sense to handle here |
| // is AddrOf. All others don't make sense as pointers. |
| UnaryOperator *U = cast<UnaryOperator>(E); |
| |
| if (U->getOpcode() == UnaryOperator::AddrOf) |
| return EvalVal(U->getSubExpr()); |
| else |
| return NULL; |
| } |
| |
| case Stmt::BinaryOperatorClass: { |
| // Handle pointer arithmetic. All other binary operators are not valid |
| // in this context. |
| BinaryOperator *B = cast<BinaryOperator>(E); |
| BinaryOperator::Opcode op = B->getOpcode(); |
| |
| if (op != BinaryOperator::Add && op != BinaryOperator::Sub) |
| return NULL; |
| |
| Expr *Base = B->getLHS(); |
| |
| // Determine which argument is the real pointer base. It could be |
| // the RHS argument instead of the LHS. |
| if (!Base->getType()->isPointerType()) Base = B->getRHS(); |
| |
| assert (Base->getType()->isPointerType()); |
| return EvalAddr(Base); |
| } |
| |
| // For conditional operators we need to see if either the LHS or RHS are |
| // valid DeclRefExpr*s. If one of them is valid, we return it. |
| case Stmt::ConditionalOperatorClass: { |
| ConditionalOperator *C = cast<ConditionalOperator>(E); |
| |
| // Handle the GNU extension for missing LHS. |
| if (Expr *lhsExpr = C->getLHS()) |
| if (DeclRefExpr* LHS = EvalAddr(lhsExpr)) |
| return LHS; |
| |
| return EvalAddr(C->getRHS()); |
| } |
| |
| // For casts, we need to handle conversions from arrays to |
| // pointer values, and pointer-to-pointer conversions. |
| case Stmt::ImplicitCastExprClass: |
| case Stmt::CStyleCastExprClass: |
| case Stmt::CXXFunctionalCastExprClass: { |
| Expr* SubExpr = cast<CastExpr>(E)->getSubExpr(); |
| QualType T = SubExpr->getType(); |
| |
| if (SubExpr->getType()->isPointerType() || |
| SubExpr->getType()->isBlockPointerType() || |
| SubExpr->getType()->isObjCQualifiedIdType()) |
| return EvalAddr(SubExpr); |
| else if (T->isArrayType()) |
| return EvalVal(SubExpr); |
| else |
| return 0; |
| } |
| |
| // C++ casts. For dynamic casts, static casts, and const casts, we |
| // are always converting from a pointer-to-pointer, so we just blow |
| // through the cast. In the case the dynamic cast doesn't fail (and |
| // return NULL), we take the conservative route and report cases |
| // where we return the address of a stack variable. For Reinterpre |
| // FIXME: The comment about is wrong; we're not always converting |
| // from pointer to pointer. I'm guessing that this code should also |
| // handle references to objects. |
| case Stmt::CXXStaticCastExprClass: |
| case Stmt::CXXDynamicCastExprClass: |
| case Stmt::CXXConstCastExprClass: |
| case Stmt::CXXReinterpretCastExprClass: { |
| Expr *S = cast<CXXNamedCastExpr>(E)->getSubExpr(); |
| if (S->getType()->isPointerType() || S->getType()->isBlockPointerType()) |
| return EvalAddr(S); |
| else |
| return NULL; |
| } |
| |
| // Everything else: we simply don't reason about them. |
| default: |
| return NULL; |
| } |
| } |
| |
| |
| /// EvalVal - This function is complements EvalAddr in the mutual recursion. |
| /// See the comments for EvalAddr for more details. |
| static DeclRefExpr* EvalVal(Expr *E) { |
| |
| // We should only be called for evaluating non-pointer expressions, or |
| // expressions with a pointer type that are not used as references but instead |
| // are l-values (e.g., DeclRefExpr with a pointer type). |
| |
| // Our "symbolic interpreter" is just a dispatch off the currently |
| // viewed AST node. We then recursively traverse the AST by calling |
| // EvalAddr and EvalVal appropriately. |
| switch (E->getStmtClass()) { |
| case Stmt::DeclRefExprClass: |
| case Stmt::QualifiedDeclRefExprClass: { |
| // DeclRefExpr: the base case. When we hit a DeclRefExpr we are looking |
| // at code that refers to a variable's name. We check if it has local |
| // storage within the function, and if so, return the expression. |
| DeclRefExpr *DR = cast<DeclRefExpr>(E); |
| |
| if (VarDecl *V = dyn_cast<VarDecl>(DR->getDecl())) |
| if(V->hasLocalStorage() && !V->getType()->isReferenceType()) return DR; |
| |
| return NULL; |
| } |
| |
| case Stmt::ParenExprClass: |
| // Ignore parentheses. |
| return EvalVal(cast<ParenExpr>(E)->getSubExpr()); |
| |
| case Stmt::UnaryOperatorClass: { |
| // The only unary operator that make sense to handle here |
| // is Deref. All others don't resolve to a "name." This includes |
| // handling all sorts of rvalues passed to a unary operator. |
| UnaryOperator *U = cast<UnaryOperator>(E); |
| |
| if (U->getOpcode() == UnaryOperator::Deref) |
| return EvalAddr(U->getSubExpr()); |
| |
| return NULL; |
| } |
| |
| case Stmt::ArraySubscriptExprClass: { |
| // Array subscripts are potential references to data on the stack. We |
| // retrieve the DeclRefExpr* for the array variable if it indeed |
| // has local storage. |
| return EvalAddr(cast<ArraySubscriptExpr>(E)->getBase()); |
| } |
| |
| case Stmt::ConditionalOperatorClass: { |
| // For conditional operators we need to see if either the LHS or RHS are |
| // non-NULL DeclRefExpr's. If one is non-NULL, we return it. |
| ConditionalOperator *C = cast<ConditionalOperator>(E); |
| |
| // Handle the GNU extension for missing LHS. |
| if (Expr *lhsExpr = C->getLHS()) |
| if (DeclRefExpr *LHS = EvalVal(lhsExpr)) |
| return LHS; |
| |
| return EvalVal(C->getRHS()); |
| } |
| |
| // Accesses to members are potential references to data on the stack. |
| case Stmt::MemberExprClass: { |
| MemberExpr *M = cast<MemberExpr>(E); |
| |
| // Check for indirect access. We only want direct field accesses. |
| if (!M->isArrow()) |
| return EvalVal(M->getBase()); |
| else |
| return NULL; |
| } |
| |
| // Everything else: we simply don't reason about them. |
| default: |
| return NULL; |
| } |
| } |
| |
| //===--- CHECK: Floating-Point comparisons (-Wfloat-equal) ---------------===// |
| |
| /// Check for comparisons of floating point operands using != and ==. |
| /// Issue a warning if these are no self-comparisons, as they are not likely |
| /// to do what the programmer intended. |
| void Sema::CheckFloatComparison(SourceLocation loc, Expr* lex, Expr *rex) { |
| bool EmitWarning = true; |
| |
| Expr* LeftExprSansParen = lex->IgnoreParens(); |
| Expr* RightExprSansParen = rex->IgnoreParens(); |
| |
| // Special case: check for x == x (which is OK). |
| // Do not emit warnings for such cases. |
| if (DeclRefExpr* DRL = dyn_cast<DeclRefExpr>(LeftExprSansParen)) |
| if (DeclRefExpr* DRR = dyn_cast<DeclRefExpr>(RightExprSansParen)) |
| if (DRL->getDecl() == DRR->getDecl()) |
| EmitWarning = false; |
| |
| |
| // Special case: check for comparisons against literals that can be exactly |
| // represented by APFloat. In such cases, do not emit a warning. This |
| // is a heuristic: often comparison against such literals are used to |
| // detect if a value in a variable has not changed. This clearly can |
| // lead to false negatives. |
| if (EmitWarning) { |
| if (FloatingLiteral* FLL = dyn_cast<FloatingLiteral>(LeftExprSansParen)) { |
| if (FLL->isExact()) |
| EmitWarning = false; |
| } |
| else |
| if (FloatingLiteral* FLR = dyn_cast<FloatingLiteral>(RightExprSansParen)){ |
| if (FLR->isExact()) |
| EmitWarning = false; |
| } |
| } |
| |
| // Check for comparisons with builtin types. |
| if (EmitWarning) |
| if (CallExpr* CL = dyn_cast<CallExpr>(LeftExprSansParen)) |
| if (CL->isBuiltinCall(Context)) |
| EmitWarning = false; |
| |
| if (EmitWarning) |
| if (CallExpr* CR = dyn_cast<CallExpr>(RightExprSansParen)) |
| if (CR->isBuiltinCall(Context)) |
| EmitWarning = false; |
| |
| // Emit the diagnostic. |
| if (EmitWarning) |
| Diag(loc, diag::warn_floatingpoint_eq) |
| << lex->getSourceRange() << rex->getSourceRange(); |
| } |