/* * Cppcheck - A tool for static C/C++ code analysis * Copyright (C) 2007-2022 Cppcheck team. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . */ //--------------------------------------------------------------------------- // Check for condition mismatches //--------------------------------------------------------------------------- #include "checkcondition.h" #include "astutils.h" #include "library.h" #include "platform.h" #include "settings.h" #include "symboldatabase.h" #include "token.h" #include "tokenize.h" #include "valueflow.h" #include "checkother.h" // comparisonNonZeroExpressionLessThanZero and testIfNonZeroExpressionIsPositive #include #include #include #include #include #include #include #include // CWE ids used static const struct CWE uncheckedErrorConditionCWE(391U); static const struct CWE CWE398(398U); // Indicator of Poor Code Quality static const struct CWE CWE570(570U); // Expression is Always False static const struct CWE CWE571(571U); // Expression is Always True //--------------------------------------------------------------------------- // Register this check class (by creating a static instance of it) namespace { CheckCondition instance; } bool CheckCondition::diag(const Token* tok, bool insert) { if (!tok) return false; const Token* parent = tok->astParent(); bool hasParent = false; while (Token::Match(parent, "&&|%oror%")) { if (mCondDiags.count(parent) != 0) { hasParent = true; break; } parent = parent->astParent(); } if (mCondDiags.count(tok) == 0 && !hasParent) { if (insert) mCondDiags.insert(tok); return false; } return true; } bool CheckCondition::isAliased(const std::set &vars) const { for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) { if (Token::Match(tok, "= & %var% ;") && vars.find(tok->tokAt(2)->varId()) != vars.end()) return true; } return false; } void CheckCondition::assignIf() { if (!mSettings->severity.isEnabled(Severity::style)) return; for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) { if (tok->str() != "=") continue; if (Token::Match(tok->tokAt(-2), "[;{}] %var% =")) { const Variable *var = tok->previous()->variable(); if (var == nullptr) continue; char bitop = '\0'; MathLib::bigint num = 0; if (Token::Match(tok->next(), "%num% [&|]")) { bitop = tok->strAt(2).at(0); num = MathLib::toLongNumber(tok->next()->str()); } else { const Token *endToken = Token::findsimplematch(tok, ";"); // Casting address if (endToken && Token::Match(endToken->tokAt(-4), "* ) & %any% ;")) endToken = nullptr; if (endToken && Token::Match(endToken->tokAt(-2), "[&|] %num% ;")) { bitop = endToken->strAt(-2).at(0); num = MathLib::toLongNumber(endToken->previous()->str()); } } if (bitop == '\0') continue; if (num < 0 && bitop == '|') continue; assignIfParseScope(tok, tok->tokAt(4), var->declarationId(), var->isLocal(), bitop, num); } } } static bool isParameterChanged(const Token *partok) { bool addressOf = Token::Match(partok, "[(,] &"); int argumentNumber = 0; const Token *ftok; for (ftok = partok; ftok && ftok->str() != "("; ftok = ftok->previous()) { if (ftok->str() == ")") ftok = ftok->link(); else if (argumentNumber == 0U && ftok->str() == "&") addressOf = true; else if (ftok->str() == ",") argumentNumber++; } ftok = ftok ? ftok->previous() : nullptr; if (!(ftok && ftok->function())) return true; const Variable *par = ftok->function()->getArgumentVar(argumentNumber); if (!par) return true; if (par->isConst()) return false; if (addressOf || par->isReference() || par->isPointer()) return true; return false; } /** parse scopes recursively */ bool CheckCondition::assignIfParseScope(const Token * const assignTok, const Token * const startTok, const nonneg int varid, const bool islocal, const char bitop, const MathLib::bigint num) { bool ret = false; for (const Token *tok2 = startTok; tok2; tok2 = tok2->next()) { if ((bitop == '&') && Token::Match(tok2->tokAt(2), "%varid% %cop% %num% ;", varid) && tok2->strAt(3) == std::string(1U, bitop)) { const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(4)); if (0 == (num & num2)) mismatchingBitAndError(assignTok, num, tok2, num2); } if (Token::Match(tok2, "%varid% =", varid)) { return true; } if (bitop == '&' && Token::Match(tok2, "%varid% &= %num% ;", varid)) { const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(2)); if (0 == (num & num2)) mismatchingBitAndError(assignTok, num, tok2, num2); } if (Token::Match(tok2, "++|-- %varid%", varid) || Token::Match(tok2, "%varid% ++|--", varid)) return true; if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid) && isParameterChanged(tok2)) return true; if (tok2->str() == "}") return false; if (Token::Match(tok2, "break|continue|return")) ret = true; if (ret && tok2->str() == ";") return false; if (!islocal && Token::Match(tok2, "%name% (") && !Token::simpleMatch(tok2->next()->link(), ") {")) return true; if (Token::Match(tok2, "if|while (")) { if (!islocal && tok2->str() == "while") continue; if (tok2->str() == "while") { // is variable changed in loop? const Token *bodyStart = tok2->linkAt(1)->next(); const Token *bodyEnd = bodyStart ? bodyStart->link() : nullptr; if (!bodyEnd || bodyEnd->str() != "}" || isVariableChanged(bodyStart, bodyEnd, varid, !islocal, mSettings, mTokenizer->isCPP())) continue; } // parse condition const Token * const end = tok2->next()->link(); for (; tok2 != end; tok2 = tok2->next()) { if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid)) { return true; } if (Token::Match(tok2,"&&|%oror%|( %varid% ==|!= %num% &&|%oror%|)", varid)) { const Token *vartok = tok2->next(); const MathLib::bigint num2 = MathLib::toLongNumber(vartok->strAt(2)); if ((num & num2) != ((bitop=='&') ? num2 : num)) { const std::string& op(vartok->strAt(1)); const bool alwaysTrue = op == "!="; const std::string condition(vartok->str() + op + vartok->strAt(2)); assignIfError(assignTok, tok2, condition, alwaysTrue); } } if (Token::Match(tok2, "%varid% %op%", varid) && tok2->next()->isAssignmentOp()) { return true; } } const bool ret1 = assignIfParseScope(assignTok, end->tokAt(2), varid, islocal, bitop, num); bool ret2 = false; if (Token::simpleMatch(end->next()->link(), "} else {")) ret2 = assignIfParseScope(assignTok, end->next()->link()->tokAt(3), varid, islocal, bitop, num); if (ret1 || ret2) return true; } } return false; } void CheckCondition::assignIfError(const Token *tok1, const Token *tok2, const std::string &condition, bool result) { if (tok2 && diag(tok2->tokAt(2))) return; std::list locations = { tok1, tok2 }; reportError(locations, Severity::style, "assignIfError", "Mismatching assignment and comparison, comparison '" + condition + "' is always " + std::string(result ? "true" : "false") + ".", CWE398, Certainty::normal); } void CheckCondition::mismatchingBitAndError(const Token *tok1, const MathLib::bigint num1, const Token *tok2, const MathLib::bigint num2) { std::list locations = { tok1, tok2 }; std::ostringstream msg; msg << "Mismatching bitmasks. Result is always 0 (" << "X = Y & 0x" << std::hex << num1 << "; Z = X & 0x" << std::hex << num2 << "; => Z=0)."; reportError(locations, Severity::style, "mismatchingBitAnd", msg.str(), CWE398, Certainty::normal); } static void getnumchildren(const Token *tok, std::list &numchildren) { if (tok->astOperand1() && tok->astOperand1()->isNumber()) numchildren.push_back(MathLib::toLongNumber(tok->astOperand1()->str())); else if (tok->astOperand1() && tok->str() == tok->astOperand1()->str()) getnumchildren(tok->astOperand1(), numchildren); if (tok->astOperand2() && tok->astOperand2()->isNumber()) numchildren.push_back(MathLib::toLongNumber(tok->astOperand2()->str())); else if (tok->astOperand2() && tok->str() == tok->astOperand2()->str()) getnumchildren(tok->astOperand2(), numchildren); } /* Return whether tok is in the body for a function returning a boolean. */ static bool inBooleanFunction(const Token *tok) { const Scope *scope = tok ? tok->scope() : nullptr; while (scope && scope->isLocal()) scope = scope->nestedIn; if (scope && scope->type == Scope::eFunction) { const Function *func = scope->function; if (func) { const Token *ret = func->retDef; while (Token::Match(ret, "static|const")) ret = ret->next(); return Token::Match(ret, "bool|_Bool"); } } return false; } void CheckCondition::checkBadBitmaskCheck() { if (!mSettings->severity.isEnabled(Severity::warning)) return; for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) { if (tok->str() == "|" && tok->astOperand1() && tok->astOperand2() && tok->astParent()) { const Token* parent = tok->astParent(); const bool isBoolean = Token::Match(parent, "&&|%oror%") || (parent->str() == "?" && parent->astOperand1() == tok) || (parent->str() == "=" && parent->astOperand2() == tok && parent->astOperand1() && parent->astOperand1()->variable() && Token::Match(parent->astOperand1()->variable()->typeStartToken(), "bool|_Bool")) || (parent->str() == "(" && Token::Match(parent->astOperand1(), "if|while")) || (parent->str() == "return" && parent->astOperand1() == tok && inBooleanFunction(tok)); const bool isTrue = (tok->astOperand1()->hasKnownIntValue() && tok->astOperand1()->values().front().intvalue != 0) || (tok->astOperand2()->hasKnownIntValue() && tok->astOperand2()->values().front().intvalue != 0); if (isBoolean && isTrue) badBitmaskCheckError(tok); } } } void CheckCondition::badBitmaskCheckError(const Token *tok) { reportError(tok, Severity::warning, "badBitmaskCheck", "Result of operator '|' is always true if one operand is non-zero. Did you intend to use '&'?", CWE571, Certainty::normal); } void CheckCondition::comparison() { if (!mSettings->severity.isEnabled(Severity::style)) return; for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) { if (!tok->isComparisonOp()) continue; const Token *expr1 = tok->astOperand1(); const Token *expr2 = tok->astOperand2(); if (!expr1 || !expr2) continue; if (expr1->isNumber()) std::swap(expr1,expr2); if (!expr2->isNumber()) continue; const MathLib::bigint num2 = MathLib::toLongNumber(expr2->str()); if (num2 < 0) continue; if (!Token::Match(expr1,"[&|]")) continue; std::list numbers; getnumchildren(expr1, numbers); for (const MathLib::bigint num1 : numbers) { if (num1 < 0) continue; if (Token::Match(tok, "==|!=")) { if ((expr1->str() == "&" && (num1 & num2) != num2) || (expr1->str() == "|" && (num1 | num2) != num2)) { const std::string& op(tok->str()); comparisonError(expr1, expr1->str(), num1, op, num2, op=="==" ? false : true); } } else if (expr1->str() == "&") { const bool or_equal = Token::Match(tok, ">=|<="); const std::string& op(tok->str()); if ((Token::Match(tok, ">=|<")) && (num1 < num2)) { comparisonError(expr1, expr1->str(), num1, op, num2, or_equal ? false : true); } else if ((Token::Match(tok, "<=|>")) && (num1 <= num2)) { comparisonError(expr1, expr1->str(), num1, op, num2, or_equal ? true : false); } } else if (expr1->str() == "|") { if ((expr1->astOperand1()->valueType()) && (expr1->astOperand1()->valueType()->sign == ValueType::Sign::UNSIGNED)) { const bool or_equal = Token::Match(tok, ">=|<="); const std::string& op(tok->str()); if ((Token::Match(tok, ">=|<")) && (num1 >= num2)) { //"(a | 0x07) >= 7U" is always true for unsigned a //"(a | 0x07) < 7U" is always false for unsigned a comparisonError(expr1, expr1->str(), num1, op, num2, or_equal ? true : false); } else if ((Token::Match(tok, "<=|>")) && (num1 > num2)) { //"(a | 0x08) <= 7U" is always false for unsigned a //"(a | 0x07) > 6U" is always true for unsigned a comparisonError(expr1, expr1->str(), num1, op, num2, or_equal ? false : true); } } } } } } void CheckCondition::comparisonError(const Token *tok, const std::string &bitop, MathLib::bigint value1, const std::string &op, MathLib::bigint value2, bool result) { std::ostringstream expression; expression << std::hex << "(X " << bitop << " 0x" << value1 << ") " << op << " 0x" << value2; const std::string errmsg("Expression '" + expression.str() + "' is always " + (result?"true":"false") + ".\n" "The expression '" + expression.str() + "' is always " + (result?"true":"false") + ". Check carefully constants and operators used, these errors might be hard to " "spot sometimes. In case of complex expression it might help to split it to " "separate expressions."); reportError(tok, Severity::style, "comparisonError", errmsg, CWE398, Certainty::normal); } bool CheckCondition::isOverlappingCond(const Token * const cond1, const Token * const cond2, bool pure) const { if (!cond1 || !cond2) return false; // same expressions if (isSameExpression(mTokenizer->isCPP(), true, cond1, cond2, mSettings->library, pure, false)) return true; // bitwise overlap for example 'x&7' and 'x==1' if (cond1->str() == "&" && cond1->astOperand1() && cond2->astOperand2()) { const Token *expr1 = cond1->astOperand1(); const Token *num1 = cond1->astOperand2(); if (!num1) // unary operator& return false; if (!num1->isNumber()) std::swap(expr1,num1); if (!num1->isNumber() || MathLib::isNegative(num1->str())) return false; if (!Token::Match(cond2, "&|==") || !cond2->astOperand1() || !cond2->astOperand2()) return false; const Token *expr2 = cond2->astOperand1(); const Token *num2 = cond2->astOperand2(); if (!num2->isNumber()) std::swap(expr2,num2); if (!num2->isNumber() || MathLib::isNegative(num2->str())) return false; if (!isSameExpression(mTokenizer->isCPP(), true, expr1, expr2, mSettings->library, pure, false)) return false; const MathLib::bigint value1 = MathLib::toLongNumber(num1->str()); const MathLib::bigint value2 = MathLib::toLongNumber(num2->str()); if (cond2->str() == "&") return ((value1 & value2) == value2); return ((value1 & value2) > 0); } return false; } void CheckCondition::duplicateCondition() { if (!mSettings->severity.isEnabled(Severity::style)) return; const SymbolDatabase *const symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope &scope : symbolDatabase->scopeList) { if (scope.type != Scope::eIf) continue; const Token* tok2 = scope.classDef->next(); if (!tok2) continue; const Token* cond1 = tok2->astOperand2(); if (!cond1) continue; if (cond1->hasKnownIntValue()) continue; tok2 = tok2->link(); if (!Token::simpleMatch(tok2, ") {")) continue; tok2 = tok2->linkAt(1); if (!Token::simpleMatch(tok2, "} if (")) continue; const Token *cond2 = tok2->tokAt(2)->astOperand2(); if (!cond2) continue; ErrorPath errorPath; if (!isExpressionChanged(cond1, scope.classDef->next(), cond2, mSettings, mTokenizer->isCPP()) && isSameExpression(mTokenizer->isCPP(), true, cond1, cond2, mSettings->library, true, true, &errorPath)) duplicateConditionError(cond1, cond2, errorPath); } } void CheckCondition::duplicateConditionError(const Token *tok1, const Token *tok2, ErrorPath errorPath) { if (diag(tok1) & diag(tok2)) return; errorPath.emplace_back(tok1, "First condition"); errorPath.emplace_back(tok2, "Second condition"); std::string msg = "The if condition is the same as the previous if condition"; reportError(errorPath, Severity::style, "duplicateCondition", msg, CWE398, Certainty::normal); } void CheckCondition::multiCondition() { if (!mSettings->severity.isEnabled(Severity::style)) return; const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope &scope : symbolDatabase->scopeList) { if (scope.type != Scope::eIf) continue; const Token * const cond1 = scope.classDef->next()->astOperand2(); if (!cond1) continue; const Token * tok2 = scope.classDef->next(); // Check each 'else if' for (;;) { tok2 = tok2->link(); if (!Token::simpleMatch(tok2, ") {")) break; tok2 = tok2->linkAt(1); if (!Token::simpleMatch(tok2, "} else { if (")) break; tok2 = tok2->tokAt(4); if (tok2->astOperand2()) { ErrorPath errorPath; if (isOverlappingCond(cond1, tok2->astOperand2(), true)) overlappingElseIfConditionError(tok2->astOperand2(), cond1->linenr()); else if (isOppositeCond(true, mTokenizer->isCPP(), cond1, tok2->astOperand2(), mSettings->library, true, true, &errorPath)) oppositeElseIfConditionError(cond1, tok2->astOperand2(), errorPath); } } } } void CheckCondition::overlappingElseIfConditionError(const Token *tok, nonneg int line1) { if (diag(tok)) return; std::ostringstream errmsg; errmsg << "Expression is always false because 'else if' condition matches previous condition at line " << line1 << "."; reportError(tok, Severity::style, "multiCondition", errmsg.str(), CWE398, Certainty::normal); } void CheckCondition::oppositeElseIfConditionError(const Token *ifCond, const Token *elseIfCond, ErrorPath errorPath) { if (diag(ifCond) & diag(elseIfCond)) return; std::ostringstream errmsg; errmsg << "Expression is always true because 'else if' condition is opposite to previous condition at line " << ifCond->linenr() << "."; errorPath.emplace_back(ifCond, "first condition"); errorPath.emplace_back(elseIfCond, "else if condition is opposite to first condition"); reportError(errorPath, Severity::style, "multiCondition", errmsg.str(), CWE398, Certainty::normal); } //--------------------------------------------------------------------------- // - Opposite inner conditions => always false // - (TODO) Same/Overlapping inner condition => always true // - same condition after early exit => always false //--------------------------------------------------------------------------- static bool isNonConstFunctionCall(const Token *ftok, const Library &library) { if (library.isFunctionConst(ftok)) return false; const Token *obj = ftok->next()->astOperand1(); while (obj && obj->str() == ".") obj = obj->astOperand1(); if (!obj) return true; else if (obj->variable() && obj->variable()->isConst()) return false; else if (ftok->function() && ftok->function()->isConst()) return false; return true; } void CheckCondition::multiCondition2() { if (!mSettings->severity.isEnabled(Severity::warning)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope &scope : symbolDatabase->scopeList) { const Token *condTok = nullptr; if (scope.type == Scope::eIf || scope.type == Scope::eWhile) condTok = scope.classDef->next()->astOperand2(); else if (scope.type == Scope::eFor) { condTok = scope.classDef->next()->astOperand2(); if (!condTok || condTok->str() != ";") continue; condTok = condTok->astOperand2(); if (!condTok || condTok->str() != ";") continue; condTok = condTok->astOperand1(); } if (!condTok) continue; const Token * const cond1 = condTok; if (!Token::simpleMatch(scope.classDef->linkAt(1), ") {")) continue; bool functionCall = false; bool nonConstFunctionCall = false; bool nonlocal = false; // nonlocal variable used in condition std::set vars; // variables used in condition visitAstNodes(condTok, [&](const Token *cond) { if (Token::Match(cond, "%name% (")) { functionCall = true; nonConstFunctionCall = isNonConstFunctionCall(cond, mSettings->library); if (nonConstFunctionCall) return ChildrenToVisit::done; } if (cond->varId()) { vars.insert(cond->varId()); const Variable *var = cond->variable(); if (!nonlocal && var) { if (!(var->isLocal() || var->isArgument())) nonlocal = true; else if ((var->isPointer() || var->isReference()) && !Token::Match(cond->astParent(), "%oror%|&&|!")) // TODO: if var is pointer check what it points at nonlocal = true; } } else if (!nonlocal && cond->isName()) { // varid is 0. this is possibly a nonlocal variable.. nonlocal = Token::Match(cond->astParent(), "%cop%|(|[") || Token::Match(cond, "%name% .") || (mTokenizer->isCPP() && cond->str() == "this"); } else { return ChildrenToVisit::op1_and_op2; } return ChildrenToVisit::none; }); if (nonConstFunctionCall) continue; std::vector varsInCond; visitAstNodes(condTok, [&varsInCond](const Token *cond) { if (cond->variable()) { const Variable *var = cond->variable(); if (std::find(varsInCond.begin(), varsInCond.end(), var) == varsInCond.end()) varsInCond.push_back(var); } return ChildrenToVisit::op1_and_op2; }); // parse until second condition is reached.. enum MULTICONDITIONTYPE { INNER, AFTER }; const Token *tok; // Parse inner condition first and then early return condition std::vector types = {MULTICONDITIONTYPE::INNER}; if (Token::Match(scope.bodyStart, "{ return|throw|continue|break")) types.push_back(MULTICONDITIONTYPE::AFTER); for (MULTICONDITIONTYPE type:types) { if (type == MULTICONDITIONTYPE::AFTER) { tok = scope.bodyEnd->next(); } else { tok = scope.bodyStart; } const Token * const endToken = tok->scope()->bodyEnd; for (; tok && tok != endToken; tok = tok->next()) { if (isExpressionChangedAt(cond1, tok, 0, false, mSettings, mTokenizer->isCPP())) break; if (Token::Match(tok, "if|return")) { const Token * condStartToken = tok->str() == "if" ? tok->next() : tok; const Token * condEndToken = tok->str() == "if" ? condStartToken->link() : Token::findsimplematch(condStartToken, ";"); // Does condition modify tracked variables? if (isExpressionChanged(cond1, condStartToken, condEndToken, mSettings, mTokenizer->isCPP())) break; // Condition.. const Token *cond2 = tok->str() == "if" ? condStartToken->astOperand2() : condStartToken->astOperand1(); const bool isReturnVar = (tok->str() == "return" && !Token::Match(cond2, "%cop%")); ErrorPath errorPath; if (type == MULTICONDITIONTYPE::INNER) { visitAstNodes(cond1, [&](const Token* firstCondition) { if (!firstCondition) return ChildrenToVisit::none; if (firstCondition->str() == "&&") { if (!isOppositeCond(false, mTokenizer->isCPP(), firstCondition, cond2, mSettings->library, true, true)) return ChildrenToVisit::op1_and_op2; } if (!firstCondition->hasKnownIntValue()) { if (!isReturnVar && isOppositeCond(false, mTokenizer->isCPP(), firstCondition, cond2, mSettings->library, true, true, &errorPath)) { if (!isAliased(vars)) oppositeInnerConditionError(firstCondition, cond2, errorPath); } else if (!isReturnVar && isSameExpression(mTokenizer->isCPP(), true, firstCondition, cond2, mSettings->library, true, true, &errorPath)) { identicalInnerConditionError(firstCondition, cond2, errorPath); } } return ChildrenToVisit::none; }); } else { visitAstNodes(cond2, [&](const Token *secondCondition) { if (secondCondition->str() == "||" || secondCondition->str() == "&&") return ChildrenToVisit::op1_and_op2; if ((!cond1->hasKnownIntValue() || !secondCondition->hasKnownIntValue()) && isSameExpression(mTokenizer->isCPP(), true, cond1, secondCondition, mSettings->library, true, true, &errorPath)) { if (!isAliased(vars) && !mTokenizer->hasIfdef(cond1, secondCondition)) { identicalConditionAfterEarlyExitError(cond1, secondCondition, errorPath); return ChildrenToVisit::done; } } return ChildrenToVisit::none; }); } } if (Token::Match(tok, "%name% (") && isVariablesChanged(tok, tok->linkAt(1), 0, varsInCond, mSettings, mTokenizer->isCPP())) { break; } if (Token::Match(tok, "%type% (") && nonlocal && isNonConstFunctionCall(tok, mSettings->library)) // non const function call -> bailout if there are nonlocal variables break; if (Token::Match(tok, "case|break|continue|return|throw") && tok->scope() == endToken->scope()) break; if (Token::Match(tok, "[;{}] %name% :")) break; // bailout if loop is seen. // TODO: handle loops better. if (Token::Match(tok, "for|while|do")) { const Token *tok1 = tok->next(); const Token *tok2; if (Token::simpleMatch(tok, "do {")) { if (!Token::simpleMatch(tok->linkAt(1), "} while (")) break; tok2 = tok->linkAt(1)->linkAt(2); } else if (Token::Match(tok, "if|while (")) { tok2 = tok->linkAt(1); if (Token::simpleMatch(tok2, ") {")) tok2 = tok2->linkAt(1); if (!tok2) break; } else { // Incomplete code break; } bool changed = false; for (int varid : vars) { if (isVariableChanged(tok1, tok2, varid, nonlocal, mSettings, mTokenizer->isCPP())) { changed = true; break; } } if (changed) break; } if ((tok->varId() && vars.find(tok->varId()) != vars.end()) || (!tok->varId() && nonlocal) || (functionCall && tok->variable() && !tok->variable()->isLocal())) { if (Token::Match(tok, "%name% %assign%|++|--")) break; if (Token::Match(tok->astParent(), "*|.|[")) { const Token *parent = tok; while (Token::Match(parent->astParent(), ".|[") || (parent->astParent() && parent->astParent()->isUnaryOp("*"))) parent = parent->astParent(); if (Token::Match(parent->astParent(), "%assign%|++|--")) break; } if (mTokenizer->isCPP() && Token::Match(tok, "%name% <<") && (!tok->valueType() || !tok->valueType()->isIntegral())) break; if (isLikelyStreamRead(mTokenizer->isCPP(), tok->next()) || isLikelyStreamRead(mTokenizer->isCPP(), tok->previous())) break; if (Token::Match(tok, "%name% [")) { const Token *tok2 = tok->linkAt(1); while (Token::simpleMatch(tok2, "] [")) tok2 = tok2->linkAt(1); if (Token::Match(tok2, "] %assign%|++|--")) break; } if (Token::Match(tok->previous(), "++|--|& %name%")) break; if (tok->variable() && !tok->variable()->isConst() && Token::Match(tok, "%name% . %name% (")) { const Function* function = tok->tokAt(2)->function(); if (!function || !function->isConst()) break; } if (Token::Match(tok->previous(), "[(,] %name% [,)]") && isParameterChanged(tok)) break; } } } } } static std::string innerSmtString(const Token * tok) { if (!tok) return "if"; if (!tok->astTop()) return "if"; const Token * top = tok->astTop(); if (top->str() == "(" && top->astOperand1()) return top->astOperand1()->str(); return top->str(); } void CheckCondition::oppositeInnerConditionError(const Token *tok1, const Token* tok2, ErrorPath errorPath) { if (diag(tok1) & diag(tok2)) return; const std::string s1(tok1 ? tok1->expressionString() : "x"); const std::string s2(tok2 ? tok2->expressionString() : "!x"); const std::string innerSmt = innerSmtString(tok2); errorPath.emplace_back(ErrorPathItem(tok1, "outer condition: " + s1)); errorPath.emplace_back(ErrorPathItem(tok2, "opposite inner condition: " + s2)); const std::string msg("Opposite inner '" + innerSmt + "' condition leads to a dead code block.\n" "Opposite inner '" + innerSmt + "' condition leads to a dead code block (outer condition is '" + s1 + "' and inner condition is '" + s2 + "')."); reportError(errorPath, Severity::warning, "oppositeInnerCondition", msg, CWE398, Certainty::normal); } void CheckCondition::identicalInnerConditionError(const Token *tok1, const Token* tok2, ErrorPath errorPath) { if (diag(tok1) & diag(tok2)) return; const std::string s1(tok1 ? tok1->expressionString() : "x"); const std::string s2(tok2 ? tok2->expressionString() : "x"); const std::string innerSmt = innerSmtString(tok2); errorPath.emplace_back(ErrorPathItem(tok1, "outer condition: " + s1)); errorPath.emplace_back(ErrorPathItem(tok2, "identical inner condition: " + s2)); const std::string msg("Identical inner '" + innerSmt + "' condition is always true.\n" "Identical inner '" + innerSmt + "' condition is always true (outer condition is '" + s1 + "' and inner condition is '" + s2 + "')."); reportError(errorPath, Severity::warning, "identicalInnerCondition", msg, CWE398, Certainty::normal); } void CheckCondition::identicalConditionAfterEarlyExitError(const Token *cond1, const Token* cond2, ErrorPath errorPath) { if (diag(cond1) & diag(cond2)) return; const bool isReturnValue = cond2 && Token::simpleMatch(cond2->astParent(), "return"); const std::string cond(cond1 ? cond1->expressionString() : "x"); const std::string value = (cond2 && cond2->valueType() && cond2->valueType()->type == ValueType::Type::BOOL) ? "false" : "0"; errorPath.emplace_back(ErrorPathItem(cond1, "If condition '" + cond + "' is true, the function will return/exit")); errorPath.emplace_back(ErrorPathItem(cond2, (isReturnValue ? "Returning identical expression '" : "Testing identical condition '") + cond + "'")); reportError(errorPath, Severity::warning, "identicalConditionAfterEarlyExit", isReturnValue ? ("Identical condition and return expression '" + cond + "', return value is always " + value) : ("Identical condition '" + cond + "', second condition is always false"), CWE398, Certainty::normal); } //--------------------------------------------------------------------------- // if ((x != 1) || (x != 3)) // expression always true // if ((x == 1) && (x == 3)) // expression always false // if ((x < 1) && (x > 3)) // expression always false // if ((x > 3) || (x < 10)) // expression always true // if ((x > 5) && (x != 1)) // second comparison always true // // Check for suspect logic for an expression consisting of 2 comparison // expressions with a shared variable and constants and a logical operator // between them. // // Suggest a different logical operator when the logical operator between // the comparisons is probably wrong. // // Inform that second comparison is always true when first comparison is true. //--------------------------------------------------------------------------- static std::string invertOperatorForOperandSwap(std::string s) { if (s[0] == '<') s[0] = '>'; else if (s[0] == '>') s[0] = '<'; return s; } template static bool checkIntRelation(const std::string &op, const T value1, const T value2) { return (op == "==" && value1 == value2) || (op == "!=" && value1 != value2) || (op == ">" && value1 > value2) || (op == ">=" && value1 >= value2) || (op == "<" && value1 < value2) || (op == "<=" && value1 <= value2); } static bool checkFloatRelation(const std::string &op, const double value1, const double value2) { return (op == ">" && value1 > value2) || (op == ">=" && value1 >= value2) || (op == "<" && value1 < value2) || (op == "<=" && value1 <= value2); } template T getvalue3(const T value1, const T value2) { const T min = std::min(value1, value2); if (min== std::numeric_limits::max()) return min; else return min+1; // see #5895 } template<> double getvalue3(const double value1, const double value2) { return (value1 + value2) / 2.0f; } template static inline T getvalue(const int test, const T value1, const T value2) { // test: // 1 => return value that is less than both value1 and value2 // 2 => return value1 // 3 => return value that is between value1 and value2 // 4 => return value2 // 5 => return value that is larger than both value1 and value2 switch (test) { case 1: return std::numeric_limits::lowest(); case 2: return value1; case 3: return getvalue3(value1, value2); case 4: return value2; case 5: return std::numeric_limits::max(); } return 0; } static bool parseComparison(const Token *comp, bool *not1, std::string *op, std::string *value, const Token **expr, bool* inconclusive) { *not1 = false; while (comp && comp->str() == "!") { *not1 = !(*not1); comp = comp->astOperand1(); } if (!comp) return false; const Token* op1 = comp->astOperand1(); const Token* op2 = comp->astOperand2(); if (!comp->isComparisonOp() || !op1 || !op2) { *op = "!="; *value = "0"; *expr = comp; } else if (op1->isLiteral()) { if (op1->isExpandedMacro()) return false; *op = invertOperatorForOperandSwap(comp->str()); if (op1->enumerator() && op1->enumerator()->value_known) *value = MathLib::toString(op1->enumerator()->value); else *value = op1->str(); *expr = op2; } else if (comp->astOperand2()->isLiteral()) { if (op2->isExpandedMacro()) return false; *op = comp->str(); if (op2->enumerator() && op2->enumerator()->value_known) *value = MathLib::toString(op2->enumerator()->value); else *value = op2->str(); *expr = op1; } else { *op = "!="; *value = "0"; *expr = comp; } *inconclusive = *inconclusive || ((*value)[0] == '\'' && !(*op == "!=" || *op == "==")); // Only float and int values are currently handled if (!MathLib::isInt(*value) && !MathLib::isFloat(*value) && (*value)[0] != '\'') return false; return true; } static std::string conditionString(bool not1, const Token *expr1, const std::string &op, const std::string &value1) { if (expr1->astParent()->isComparisonOp()) return std::string(not1 ? "!(" : "") + (expr1->isName() ? expr1->str() : std::string("EXPR")) + " " + op + " " + value1 + (not1 ? ")" : ""); return std::string(not1 ? "!" : "") + (expr1->isName() ? expr1->str() : std::string("EXPR")); } static std::string conditionString(const Token * tok) { if (!tok) return ""; if (tok->isComparisonOp()) { bool inconclusive = false; bool not_; std::string op, value; const Token *expr; if (parseComparison(tok, ¬_, &op, &value, &expr, &inconclusive) && expr->isName()) { return conditionString(not_, expr, op, value); } } if (Token::Match(tok, "%cop%|&&|%oror%")) { if (tok->astOperand2()) return conditionString(tok->astOperand1()) + " " + tok->str() + " " + conditionString(tok->astOperand2()); return tok->str() + "(" + conditionString(tok->astOperand1()) + ")"; } return tok->expressionString(); } static bool isIfConstexpr(const Token* tok) { const Token* const top = tok->astTop(); return top && Token::simpleMatch(top->astOperand1(), "if") && top->astOperand1()->isConstexpr(); } void CheckCondition::checkIncorrectLogicOperator() { const bool printStyle = mSettings->severity.isEnabled(Severity::style); const bool printWarning = mSettings->severity.isEnabled(Severity::warning); if (!printWarning && !printStyle) return; const bool printInconclusive = mSettings->certainty.isEnabled(Certainty::inconclusive); const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) { if (!Token::Match(tok, "%oror%|&&") || !tok->astOperand1() || !tok->astOperand2()) continue; // 'A && (!A || B)' is equivalent to 'A && B' // 'A || (!A && B)' is equivalent to 'A || B' // 'A && (A || B)' is equivalent to 'A' // 'A || (A && B)' is equivalent to 'A' if (printStyle && ((tok->str() == "||" && tok->astOperand2()->str() == "&&") || (tok->str() == "&&" && tok->astOperand2()->str() == "||"))) { const Token* tok2 = tok->astOperand2()->astOperand1(); if (isOppositeCond(true, mTokenizer->isCPP(), tok->astOperand1(), tok2, mSettings->library, true, false)) { std::string expr1(tok->astOperand1()->expressionString()); std::string expr2(tok->astOperand2()->astOperand1()->expressionString()); std::string expr3(tok->astOperand2()->astOperand2()->expressionString()); // make copy for later because the original string might get overwritten const std::string expr1VerboseMsg = expr1; const std::string expr2VerboseMsg = expr2; const std::string expr3VerboseMsg = expr3; if (expr1.length() + expr2.length() + expr3.length() > 50U) { if (expr1[0] == '!' && expr2[0] != '!') { expr1 = "!A"; expr2 = "A"; } else { expr1 = "A"; expr2 = "!A"; } expr3 = "B"; } const std::string cond1 = expr1 + " " + tok->str() + " (" + expr2 + " " + tok->astOperand2()->str() + " " + expr3 + ")"; const std::string cond2 = expr1 + " " + tok->str() + " " + expr3; const std::string cond1VerboseMsg = expr1VerboseMsg + " " + tok->str() + " " + expr2VerboseMsg + " " + tok->astOperand2()->str() + " " + expr3VerboseMsg; const std::string cond2VerboseMsg = expr1VerboseMsg + " " + tok->str() + " " + expr3VerboseMsg; // for the --verbose message, transform the actual condition and print it const std::string msg = tok2->expressionString() + ". '" + cond1 + "' is equivalent to '" + cond2 + "'\n" "The condition '" + cond1VerboseMsg + "' is equivalent to '" + cond2VerboseMsg + "'."; redundantConditionError(tok, msg, false); continue; } else if (isSameExpression(mTokenizer->isCPP(), false, tok->astOperand1(), tok2, mSettings->library, true, true)) { std::string expr1(tok->astOperand1()->expressionString()); std::string expr2(tok->astOperand2()->astOperand1()->expressionString()); std::string expr3(tok->astOperand2()->astOperand2()->expressionString()); // make copy for later because the original string might get overwritten const std::string expr1VerboseMsg = expr1; const std::string expr2VerboseMsg = expr2; const std::string expr3VerboseMsg = expr3; if (expr1.length() + expr2.length() + expr3.length() > 50U) { expr1 = "A"; expr2 = "A"; expr3 = "B"; } const std::string cond1 = expr1 + " " + tok->str() + " (" + expr2 + " " + tok->astOperand2()->str() + " " + expr3 + ")"; const std::string cond2 = expr1; const std::string cond1VerboseMsg = expr1VerboseMsg + " " + tok->str() + " " + expr2VerboseMsg + " " + tok->astOperand2()->str() + " " + expr3VerboseMsg; const std::string& cond2VerboseMsg = expr1VerboseMsg; // for the --verbose message, transform the actual condition and print it const std::string msg = tok2->expressionString() + ". '" + cond1 + "' is equivalent to '" + cond2 + "'\n" "The condition '" + cond1VerboseMsg + "' is equivalent to '" + cond2VerboseMsg + "'."; redundantConditionError(tok, msg, false); continue; } } // Comparison #1 (LHS) const Token *comp1 = tok->astOperand1(); if (comp1->str() == tok->str()) comp1 = comp1->astOperand2(); // Comparison #2 (RHS) const Token *comp2 = tok->astOperand2(); bool inconclusive = false; bool parseable = true; // Parse LHS bool not1; std::string op1, value1; const Token *expr1 = nullptr; parseable &= (parseComparison(comp1, ¬1, &op1, &value1, &expr1, &inconclusive)); // Parse RHS bool not2; std::string op2, value2; const Token *expr2 = nullptr; parseable &= (parseComparison(comp2, ¬2, &op2, &value2, &expr2, &inconclusive)); if (inconclusive && !printInconclusive) continue; const bool isUnknown = (expr1 && expr1->valueType() && expr1->valueType()->type == ValueType::UNKNOWN_TYPE) || (expr2 && expr2->valueType() && expr2->valueType()->type == ValueType::UNKNOWN_TYPE); if (isUnknown) continue; const bool isfloat = astIsFloat(expr1, true) || MathLib::isFloat(value1) || astIsFloat(expr2, true) || MathLib::isFloat(value2); ErrorPath errorPath; // Opposite comparisons around || or && => always true or always false const bool isLogicalOr(tok->str() == "||"); if (!isfloat && isOppositeCond(isLogicalOr, mTokenizer->isCPP(), tok->astOperand1(), tok->astOperand2(), mSettings->library, true, true, &errorPath)) { if (!isIfConstexpr(tok)) { const bool alwaysTrue(isLogicalOr); incorrectLogicOperatorError(tok, conditionString(tok), alwaysTrue, inconclusive, errorPath); } continue; } if (!parseable) continue; if (isSameExpression(mTokenizer->isCPP(), true, comp1, comp2, mSettings->library, true, true)) continue; // same expressions => only report that there are same expressions if (!isSameExpression(mTokenizer->isCPP(), true, expr1, expr2, mSettings->library, true, true)) continue; // don't check floating point equality comparisons. that is bad // and deserves different warnings. if (isfloat && (op1 == "==" || op1 == "!=" || op2 == "==" || op2 == "!=")) continue; const double d1 = (isfloat) ? MathLib::toDoubleNumber(value1) : 0; const double d2 = (isfloat) ? MathLib::toDoubleNumber(value2) : 0; const MathLib::bigint i1 = (isfloat) ? 0 : MathLib::toLongNumber(value1); const MathLib::bigint i2 = (isfloat) ? 0 : MathLib::toLongNumber(value2); const bool useUnsignedInt = (std::numeric_limits::max()==i1) || (std::numeric_limits::max()==i2); const MathLib::biguint u1 = (useUnsignedInt) ? MathLib::toLongNumber(value1) : 0; const MathLib::biguint u2 = (useUnsignedInt) ? MathLib::toLongNumber(value2) : 0; // evaluate if expression is always true/false bool alwaysTrue = true, alwaysFalse = true; bool firstTrue = true, secondTrue = true; for (int test = 1; test <= 5; ++test) { // test: // 1 => testvalue is less than both value1 and value2 // 2 => testvalue is value1 // 3 => testvalue is between value1 and value2 // 4 => testvalue value2 // 5 => testvalue is larger than both value1 and value2 bool result1, result2; if (isfloat) { const double testvalue = getvalue(test, d1, d2); result1 = checkFloatRelation(op1, testvalue, d1); result2 = checkFloatRelation(op2, testvalue, d2); } else if (useUnsignedInt) { const MathLib::biguint testvalue = getvalue(test, u1, u2); result1 = checkIntRelation(op1, testvalue, u1); result2 = checkIntRelation(op2, testvalue, u2); } else { const MathLib::bigint testvalue = getvalue(test, i1, i2); result1 = checkIntRelation(op1, testvalue, i1); result2 = checkIntRelation(op2, testvalue, i2); } if (not1) result1 = !result1; if (not2) result2 = !result2; if (tok->str() == "&&") { alwaysTrue &= (result1 && result2); alwaysFalse &= !(result1 && result2); } else { alwaysTrue &= (result1 || result2); alwaysFalse &= !(result1 || result2); } firstTrue &= !(!result1 && result2); secondTrue &= !(result1 && !result2); } const std::string cond1str = conditionString(not1, expr1, op1, value1); const std::string cond2str = conditionString(not2, expr2, op2, value2); if (printWarning && (alwaysTrue || alwaysFalse)) { const std::string text = cond1str + " " + tok->str() + " " + cond2str; incorrectLogicOperatorError(tok, text, alwaysTrue, inconclusive, errorPath); } else if (printStyle && secondTrue) { const std::string text = "If '" + cond1str + "', the comparison '" + cond2str + "' is always true."; redundantConditionError(tok, text, inconclusive); } else if (printStyle && firstTrue) { //const std::string text = "The comparison " + cond1str + " is always " + // (firstTrue ? "true" : "false") + " when " + // cond2str + "."; const std::string text = "If '" + cond2str + "', the comparison '" + cond1str + "' is always true."; redundantConditionError(tok, text, inconclusive); } } } } void CheckCondition::incorrectLogicOperatorError(const Token *tok, const std::string &condition, bool always, bool inconclusive, ErrorPath errors) { if (diag(tok)) return; errors.emplace_back(tok, ""); if (always) reportError(errors, Severity::warning, "incorrectLogicOperator", "Logical disjunction always evaluates to true: " + condition + ".\n" "Logical disjunction always evaluates to true: " + condition + ". " "Are these conditions necessary? Did you intend to use && instead? Are the numbers correct? Are you comparing the correct variables?", CWE571, inconclusive ? Certainty::inconclusive : Certainty::normal); else reportError(errors, Severity::warning, "incorrectLogicOperator", "Logical conjunction always evaluates to false: " + condition + ".\n" "Logical conjunction always evaluates to false: " + condition + ". " "Are these conditions necessary? Did you intend to use || instead? Are the numbers correct? Are you comparing the correct variables?", CWE570, inconclusive ? Certainty::inconclusive : Certainty::normal); } void CheckCondition::redundantConditionError(const Token *tok, const std::string &text, bool inconclusive) { if (diag(tok)) return; reportError(tok, Severity::style, "redundantCondition", "Redundant condition: " + text, CWE398, inconclusive ? Certainty::inconclusive : Certainty::normal); } //----------------------------------------------------------------------------- // Detect "(var % val1) > val2" where val2 is >= val1. //----------------------------------------------------------------------------- void CheckCondition::checkModuloAlwaysTrueFalse() { if (!mSettings->severity.isEnabled(Severity::warning)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) { if (!tok->isComparisonOp()) continue; const Token *num, *modulo; if (Token::simpleMatch(tok->astOperand1(), "%") && Token::Match(tok->astOperand2(), "%num%")) { modulo = tok->astOperand1(); num = tok->astOperand2(); } else if (Token::Match(tok->astOperand1(), "%num%") && Token::simpleMatch(tok->astOperand2(), "%")) { num = tok->astOperand1(); modulo = tok->astOperand2(); } else { continue; } if (Token::Match(modulo->astOperand2(), "%num%") && MathLib::isLessEqual(modulo->astOperand2()->str(), num->str())) moduloAlwaysTrueFalseError(tok, modulo->astOperand2()->str()); } } } void CheckCondition::moduloAlwaysTrueFalseError(const Token* tok, const std::string& maxVal) { reportError(tok, Severity::warning, "moduloAlwaysTrueFalse", "Comparison of modulo result is predetermined, because it is always less than " + maxVal + ".", CWE398, Certainty::normal); } static int countPar(const Token *tok1, const Token *tok2) { int par = 0; for (const Token *tok = tok1; tok && tok != tok2; tok = tok->next()) { if (tok->str() == "(") ++par; else if (tok->str() == ")") --par; else if (tok->str() == ";") return -1; } return par; } //--------------------------------------------------------------------------- // Clarify condition '(x = a < 0)' into '((x = a) < 0)' or '(x = (a < 0))' // Clarify condition '(a & b == c)' into '((a & b) == c)' or '(a & (b == c))' //--------------------------------------------------------------------------- void CheckCondition::clarifyCondition() { if (!mSettings->severity.isEnabled(Severity::style)) return; const bool isC = mTokenizer->isC(); const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) { if (Token::Match(tok, "( %name% [=&|^]")) { for (const Token *tok2 = tok->tokAt(3); tok2; tok2 = tok2->next()) { if (tok2->str() == "(" || tok2->str() == "[") tok2 = tok2->link(); else if (tok2->isComparisonOp()) { // This might be a template if (!isC && tok2->link()) break; if (Token::simpleMatch(tok2->astParent(), "?")) break; clarifyConditionError(tok, tok->strAt(2) == "=", false); break; } else if (!tok2->isName() && !tok2->isNumber() && tok2->str() != ".") break; } } else if (tok->tokType() == Token::eBitOp && !tok->isUnaryOp("&")) { if (tok->astOperand2() && tok->astOperand2()->variable() && tok->astOperand2()->variable()->nameToken() == tok->astOperand2()) continue; // using boolean result in bitwise operation ! x [&|^] const ValueType* vt1 = tok->astOperand1() ? tok->astOperand1()->valueType() : nullptr; const ValueType* vt2 = tok->astOperand2() ? tok->astOperand2()->valueType() : nullptr; if (vt1 && vt1->type == ValueType::BOOL && !Token::Match(tok->astOperand1(), "%name%|(|[|::|.") && countPar(tok->astOperand1(), tok) == 0) clarifyConditionError(tok, false, true); else if (vt2 && vt2->type == ValueType::BOOL && !Token::Match(tok->astOperand2(), "%name%|(|[|::|.") && countPar(tok, tok->astOperand2()) == 0) clarifyConditionError(tok, false, true); } } } } void CheckCondition::clarifyConditionError(const Token *tok, bool assign, bool boolop) { std::string errmsg; if (assign) errmsg = "Suspicious condition (assignment + comparison); Clarify expression with parentheses."; else if (boolop) errmsg = "Boolean result is used in bitwise operation. Clarify expression with parentheses.\n" "Suspicious expression. Boolean result is used in bitwise operation. The operator '!' " "and the comparison operators have higher precedence than bitwise operators. " "It is recommended that the expression is clarified with parentheses."; else errmsg = "Suspicious condition (bitwise operator + comparison); Clarify expression with parentheses.\n" "Suspicious condition. Comparison operators have higher precedence than bitwise operators. " "Please clarify the condition with parentheses."; reportError(tok, Severity::style, "clarifyCondition", errmsg, CWE398, Certainty::normal); } void CheckCondition::alwaysTrueFalse() { if (!mSettings->severity.isEnabled(Severity::style)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) { if (Token::simpleMatch(tok, "<") && tok->link()) // don't write false positives when templates are used continue; if (!tok->hasKnownIntValue()) continue; if (Token::Match(tok->previous(), "%name% (") && tok->previous()->function()) { const Function* f = tok->previous()->function(); if (f->functionScope && Token::Match(f->functionScope->bodyStart, "{ return true|false ;")) continue; } { // is this a condition.. const Token *parent = tok->astParent(); while (Token::Match(parent, "%oror%|&&")) parent = parent->astParent(); if (!parent) continue; const Token *condition = nullptr; if (parent->str() == "?" && precedes(tok, parent)) condition = parent->astOperand1(); else if (Token::Match(parent->previous(), "if|while (")) condition = parent->astOperand2(); else if (Token::simpleMatch(parent, "return")) condition = parent->astOperand1(); else if (parent->str() == ";" && parent->astParent() && parent->astParent()->astParent() && Token::simpleMatch(parent->astParent()->astParent()->previous(), "for (")) condition = parent->astOperand1(); else continue; (void)condition; } // Skip already diagnosed values if (diag(tok, false)) continue; if (Token::Match(tok, "%num%|%bool%|%char%")) continue; if (Token::Match(tok, "! %num%|%bool%|%char%")) continue; if (Token::Match(tok, "%oror%|&&|:")) continue; if (Token::Match(tok, "%comp%") && isSameExpression(mTokenizer->isCPP(), true, tok->astOperand1(), tok->astOperand2(), mSettings->library, true, true)) continue; if (isConstVarExpression(tok, "[|(|&|+|-|*|/|%|^|>>|<<")) continue; // there are specific warnings about nonzero expressions (pointer/unsigned) // do not write alwaysTrueFalse for these comparisons. { const ValueFlow::Value *zeroValue = nullptr; const Token *nonZeroExpr = nullptr; if (CheckOther::comparisonNonZeroExpressionLessThanZero(tok, &zeroValue, &nonZeroExpr) || CheckOther::testIfNonZeroExpressionIsPositive(tok, &zeroValue, &nonZeroExpr)) continue; } const bool constIfWhileExpression = tok->astParent() && Token::Match(tok->astTop()->astOperand1(), "if|while") && !tok->astTop()->astOperand1()->isConstexpr() && (Token::Match(tok->astParent(), "%oror%|&&") || Token::Match(tok->astParent()->astOperand1(), "if|while")); const bool constValExpr = tok->isNumber() && Token::Match(tok->astParent(),"%oror%|&&|?"); // just one number in boolean expression const bool compExpr = Token::Match(tok, "%comp%|!"); // a compare expression const bool ternaryExpression = Token::simpleMatch(tok->astParent(), "?"); const bool returnExpression = Token::simpleMatch(tok->astTop(), "return") && (tok->isComparisonOp() || Token::Match(tok, "&&|%oror%")); if (!(constIfWhileExpression || constValExpr || compExpr || ternaryExpression || returnExpression)) continue; const Token* expr1 = tok->astOperand1(), *expr2 = tok->astOperand2(); const bool isUnknown = (expr1 && expr1->valueType() && expr1->valueType()->type == ValueType::UNKNOWN_TYPE) || (expr2 && expr2->valueType() && expr2->valueType()->type == ValueType::UNKNOWN_TYPE); if (isUnknown) continue; // Don't warn when there are expanded macros.. bool isExpandedMacro = false; visitAstNodes(tok, [&](const Token * tok2) { if (!tok2) return ChildrenToVisit::none; if (tok2->isExpandedMacro()) { isExpandedMacro = true; return ChildrenToVisit::done; } return ChildrenToVisit::op1_and_op2; }); if (isExpandedMacro) continue; for (const Token *parent = tok; parent; parent = parent->astParent()) { if (parent->isExpandedMacro()) { isExpandedMacro = true; break; } } if (isExpandedMacro) continue; // don't warn when condition checks sizeof result bool hasSizeof = false; visitAstNodes(tok, [&](const Token * tok2) { if (!tok2) return ChildrenToVisit::none; if (tok2->isNumber()) return ChildrenToVisit::none; if (Token::simpleMatch(tok2->previous(), "sizeof (")) { hasSizeof = true; return ChildrenToVisit::none; } if (tok2->isComparisonOp() || tok2->isArithmeticalOp()) { return ChildrenToVisit::op1_and_op2; } return ChildrenToVisit::none; }); if (hasSizeof) continue; if (isIfConstexpr(tok)) continue; alwaysTrueFalseError(tok, &tok->values().front()); } } } void CheckCondition::alwaysTrueFalseError(const Token *tok, const ValueFlow::Value *value) { const bool alwaysTrue = value && (value->intvalue != 0); const std::string expr = tok ? tok->expressionString() : std::string("x"); const std::string errmsg = "Condition '" + expr + "' is always " + (alwaysTrue ? "true" : "false"); const ErrorPath errorPath = getErrorPath(tok, value, errmsg); reportError(errorPath, Severity::style, "knownConditionTrueFalse", errmsg, (alwaysTrue ? CWE571 : CWE570), Certainty::normal); } void CheckCondition::checkInvalidTestForOverflow() { // Interesting blogs: // https://www.airs.com/blog/archives/120 // https://kristerw.blogspot.com/2016/02/how-undefined-signed-overflow-enables.html // https://research.checkpoint.com/2020/optout-compiler-undefined-behavior-optimizations/ // x + c < x -> false // x + c <= x -> false // x + c > x -> true // x + c >= x -> true // x + y < x -> y < 0 if (!mSettings->severity.isEnabled(Severity::warning)) return; for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) { if (!Token::Match(tok, "<|<=|>=|>") || !tok->isBinaryOp()) continue; const Token *lhsTokens[2] = {tok->astOperand1(), tok->astOperand2()}; for (const Token *lhs: lhsTokens) { std::string cmp = tok->str(); if (lhs == tok->astOperand2()) cmp[0] = (cmp[0] == '<') ? '>' : '<'; if (!Token::Match(lhs, "[+-]") || !lhs->isBinaryOp()) continue; const bool isSignedInteger = lhs->valueType() && lhs->valueType()->isIntegral() && lhs->valueType()->sign == ValueType::Sign::SIGNED; const bool isPointer = lhs->valueType() && lhs->valueType()->pointer > 0; if (!isSignedInteger && !isPointer) continue; const Token *exprTokens[2] = {lhs->astOperand1(), lhs->astOperand2()}; for (const Token *expr: exprTokens) { if (lhs->str() == "-" && expr == lhs->astOperand2()) continue; // TODO? if (expr->hasKnownIntValue()) continue; if (!isSameExpression(mTokenizer->isCPP(), true, expr, lhs->astSibling(), mSettings->library, true, false)) continue; const Token * const other = expr->astSibling(); // x [+-] c cmp x if ((other->isNumber() && other->getKnownIntValue() > 0) || (!other->isNumber() && other->valueType() && other->valueType()->isIntegral() && other->valueType()->sign == ValueType::Sign::UNSIGNED)) { bool result; if (lhs->str() == "+") result = (cmp == ">" || cmp == ">="); else result = (cmp == "<" || cmp == "<="); invalidTestForOverflow(tok, lhs->valueType(), result ? "true" : "false"); continue; } // x + y cmp x if (lhs->str() == "+" && other->varId() > 0) { const std::string result = other->str() + cmp + "0"; invalidTestForOverflow(tok, lhs->valueType(), result); continue; } // x - y cmp x if (lhs->str() == "-" && other->varId() > 0) { std::string cmp2 = cmp; cmp2[0] = (cmp[0] == '<') ? '>' : '<'; const std::string result = other->str() + cmp2 + "0"; invalidTestForOverflow(tok, lhs->valueType(), result); continue; } } } } } void CheckCondition::invalidTestForOverflow(const Token* tok, const ValueType *valueType, const std::string &replace) { const std::string expr = (tok ? tok->expressionString() : std::string("x + c < x")); const std::string overflow = (valueType && valueType->pointer) ? "pointer overflow" : "signed integer overflow"; std::string errmsg = "Invalid test for overflow '" + expr + "'; " + overflow + " is undefined behavior."; if (replace == "false" || replace == "true") errmsg += " Some mainstream compilers remove such overflow tests when optimising the code and assume it's always " + replace + "."; else errmsg += " Some mainstream compilers removes handling of overflows when optimising the code and change the code to '" + replace + "'."; reportError(tok, Severity::warning, "invalidTestForOverflow", errmsg, uncheckedErrorConditionCWE, Certainty::normal); } void CheckCondition::checkPointerAdditionResultNotNull() { if (!mSettings->severity.isEnabled(Severity::warning)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) { if (!tok->isComparisonOp() || !tok->astOperand1() || !tok->astOperand2()) continue; // Macros might have pointless safety checks if (tok->isExpandedMacro()) continue; const Token *calcToken, *exprToken; if (tok->astOperand1()->str() == "+") { calcToken = tok->astOperand1(); exprToken = tok->astOperand2(); } else if (tok->astOperand2()->str() == "+") { calcToken = tok->astOperand2(); exprToken = tok->astOperand1(); } else continue; // pointer comparison against NULL (ptr+12==0) if (calcToken->hasKnownIntValue()) continue; if (!calcToken->valueType() || calcToken->valueType()->pointer==0) continue; if (!exprToken->hasKnownIntValue() || !exprToken->getValue(0)) continue; pointerAdditionResultNotNullError(tok, calcToken); } } } void CheckCondition::pointerAdditionResultNotNullError(const Token *tok, const Token *calc) { const std::string s = calc ? calc->expressionString() : "ptr+1"; reportError(tok, Severity::warning, "pointerAdditionResultNotNull", "Comparison is wrong. Result of '" + s + "' can't be 0 unless there is pointer overflow, and pointer overflow is undefined behaviour."); } void CheckCondition::checkDuplicateConditionalAssign() { if (!mSettings->severity.isEnabled(Severity::style)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope *scope : symbolDatabase->functionScopes) { for (const Token *tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) { if (!Token::simpleMatch(tok, "if (")) continue; if (!Token::simpleMatch(tok->next()->link(), ") {")) continue; const Token *blockTok = tok->next()->link()->next(); const Token *condTok = tok->next()->astOperand2(); if (!Token::Match(condTok, "==|!=")) continue; if (condTok->str() == "!=" && Token::simpleMatch(blockTok->link(), "} else {")) continue; if (!blockTok->next()) continue; const Token *assignTok = blockTok->next()->astTop(); if (!Token::simpleMatch(assignTok, "=")) continue; if (nextAfterAstRightmostLeaf(assignTok) != blockTok->link()->previous()) continue; if (!isSameExpression( mTokenizer->isCPP(), true, condTok->astOperand1(), assignTok->astOperand1(), mSettings->library, true, true)) continue; if (!isSameExpression( mTokenizer->isCPP(), true, condTok->astOperand2(), assignTok->astOperand2(), mSettings->library, true, true)) continue; duplicateConditionalAssignError(condTok, assignTok); } } } void CheckCondition::duplicateConditionalAssignError(const Token *condTok, const Token* assignTok) { ErrorPath errors; std::string msg = "Duplicate expression for the condition and assignment."; if (condTok && assignTok) { if (condTok->str() == "==") { msg = "Assignment '" + assignTok->expressionString() + "' is redundant with condition '" + condTok->expressionString() + "'."; errors.emplace_back(condTok, "Condition '" + condTok->expressionString() + "'"); errors.emplace_back(assignTok, "Assignment '" + assignTok->expressionString() + "' is redundant"); } else { msg = "The statement 'if (" + condTok->expressionString() + ") " + assignTok->expressionString() + "' is logically equivalent to '" + assignTok->expressionString() + "'."; errors.emplace_back(assignTok, "Assignment '" + assignTok->expressionString() + "'"); errors.emplace_back(condTok, "Condition '" + condTok->expressionString() + "' is redundant"); } } reportError( errors, Severity::style, "duplicateConditionalAssign", msg, CWE398, Certainty::normal); } void CheckCondition::checkAssignmentInCondition() { if (!mSettings->severity.isEnabled(Severity::style)) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) { if (tok->str() != "=") continue; if (!tok->astParent()) continue; // Is this assignment of container/iterator? if (!tok->valueType()) continue; if (tok->valueType()->pointer > 0) continue; if (tok->valueType()->type != ValueType::Type::CONTAINER && tok->valueType()->type != ValueType::Type::ITERATOR) continue; // warn if this is a conditional expression.. if (Token::Match(tok->astParent()->previous(), "if|while (")) assignmentInCondition(tok); else if (Token::Match(tok->astParent(), "%oror%|&&")) assignmentInCondition(tok); else if (Token::simpleMatch(tok->astParent(), "?") && tok == tok->astParent()->astOperand1()) assignmentInCondition(tok); } } } void CheckCondition::assignmentInCondition(const Token *eq) { std::string expr = eq ? eq->expressionString() : "x=y"; reportError( eq, Severity::style, "assignmentInCondition", "Suspicious assignment in condition. Condition '" + expr + "' is always true.", CWE571, Certainty::normal); } void CheckCondition::checkCompareValueOutOfTypeRange() { if (!mSettings->severity.isEnabled(Severity::style)) return; if (mSettings->platformType == cppcheck::Platform::PlatformType::Native || mSettings->platformType == cppcheck::Platform::PlatformType::Unspecified) return; const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase(); for (const Scope * scope : symbolDatabase->functionScopes) { for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) { if (!tok->isComparisonOp() || !tok->isBinaryOp()) continue; for (int i = 0; i < 2; ++i) { const Token * const valueTok = (i == 0) ? tok->astOperand1() : tok->astOperand2(); const Token * const typeTok = valueTok->astSibling(); if (!valueTok->hasKnownIntValue() || !typeTok->valueType() || typeTok->valueType()->pointer) continue; if (valueTok->getKnownIntValue() < 0 && valueTok->valueType() && valueTok->valueType()->sign != ValueType::Sign::SIGNED) continue; int bits = 0; switch (typeTok->valueType()->type) { case ValueType::Type::BOOL: bits = 1; break; case ValueType::Type::CHAR: bits = mSettings->char_bit; break; case ValueType::Type::SHORT: bits = mSettings->short_bit; break; case ValueType::Type::INT: bits = mSettings->int_bit; break; case ValueType::Type::LONG: bits = mSettings->long_bit; break; case ValueType::Type::LONGLONG: bits = mSettings->long_long_bit; break; default: break; } if (bits == 0 || bits >= 64) continue; const auto typeMinValue = (typeTok->valueType()->sign == ValueType::Sign::UNSIGNED) ? 0 : (-(1LL << (bits-1))); const auto unsignedTypeMaxValue = (1LL << bits) - 1LL; long long typeMaxValue; if (typeTok->valueType()->sign != ValueType::Sign::SIGNED) typeMaxValue = unsignedTypeMaxValue; else if (bits >= mSettings->int_bit && (!valueTok->valueType() || valueTok->valueType()->sign != ValueType::Sign::SIGNED)) typeMaxValue = unsignedTypeMaxValue; else typeMaxValue = unsignedTypeMaxValue / 2; bool result; if (tok->str() == "==") result = false; else if (tok->str() == "!=") result = true; else if (tok->str()[0] == '>' && i == 0) // num > var result = (valueTok->getKnownIntValue() > 0); else if (tok->str()[0] == '>' && i == 1) // var > num result = (valueTok->getKnownIntValue() < 0); else if (tok->str()[0] == '<' && i == 0) // num < var result = (valueTok->getKnownIntValue() < 0); else if (tok->str()[0] == '<' && i == 1) // var < num result = (valueTok->getKnownIntValue() > 0); if (valueTok->getKnownIntValue() < typeMinValue) { compareValueOutOfTypeRangeError(valueTok, typeTok->valueType()->str(), valueTok->getKnownIntValue(), result); } else if (valueTok->getKnownIntValue() > typeMaxValue) compareValueOutOfTypeRangeError(valueTok, typeTok->valueType()->str(), valueTok->getKnownIntValue(), result); } } } } void CheckCondition::compareValueOutOfTypeRangeError(const Token *comparison, const std::string &type, long long value, bool result) { reportError( comparison, Severity::style, "compareValueOutOfTypeRangeError", "Comparing expression of type '" + type + "' against value " + std::to_string(value) + ". Condition is always " + (result ? "true" : "false") + ".", CWE398, Certainty::normal); }