333 lines
13 KiB
C++
333 lines
13 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2014 Daniel Marjamäki and Cppcheck team.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//---------------------------------------------------------------------------
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// Check for assignment / condition mismatches
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//---------------------------------------------------------------------------
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#include "checkassignif.h"
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#include "symboldatabase.h"
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//---------------------------------------------------------------------------
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// Register this check class (by creating a static instance of it)
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namespace {
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CheckAssignIf instance;
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}
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void CheckAssignIf::assignIf()
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{
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if (!_settings->isEnabled("style"))
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return;
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
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if (tok->str() != "=")
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continue;
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if (Token::Match(tok->tokAt(-2), "[;{}] %var% =")) {
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const Variable *var = tok->previous()->variable();
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if (var == 0)
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continue;
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char bitop = '\0';
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MathLib::bigint num = 0;
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if (Token::Match(tok->next(), "%num% [&|]")) {
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bitop = tok->strAt(2).at(0);
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num = MathLib::toLongNumber(tok->next()->str());
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} else {
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const Token *endToken = Token::findsimplematch(tok, ";");
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// Casting address
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if (endToken && Token::Match(endToken->tokAt(-4), "* ) & %any% ;"))
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endToken = nullptr;
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if (endToken && Token::Match(endToken->tokAt(-2), "[&|] %num% ;")) {
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bitop = endToken->strAt(-2).at(0);
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num = MathLib::toLongNumber(endToken->previous()->str());
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}
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}
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if (bitop == '\0')
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continue;
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if (num < 0 && bitop == '|')
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continue;
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assignIfParseScope(tok, tok->tokAt(4), var->declarationId(), var->isLocal(), bitop, num);
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}
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}
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}
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/** parse scopes recursively */
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bool CheckAssignIf::assignIfParseScope(const Token * const assignTok,
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const Token * const startTok,
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const unsigned int varid,
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const bool islocal,
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const char bitop,
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const MathLib::bigint num)
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{
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bool ret = false;
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for (const Token *tok2 = startTok; tok2; tok2 = tok2->next()) {
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if (Token::Match(tok2->tokAt(2), "%varid% %cop% %num% ;", varid) && tok2->strAt(3) == std::string(1U, bitop)) {
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const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(4));
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if ((bitop == '&') && (0 == (num & num2)))
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mismatchingBitAndError(assignTok, num, tok2, num2);
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}
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if (Token::Match(tok2, "%varid% =", varid)) {
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if (Token::Match(tok2->tokAt(2), "%varid% %cop% %num% ;", varid) && tok2->strAt(3) == std::string(1U, bitop)) {
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const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(4));
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if ((bitop == '&') && (0 == (num & num2)))
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mismatchingBitAndError(assignTok, num, tok2, num2);
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}
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return true;
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}
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if (Token::Match(tok2, "++|-- %varid%", varid) || Token::Match(tok2, "%varid% ++|--", varid))
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return true;
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if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid)) {
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unsigned int argumentNumber = 0;
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const Token *ftok;
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for (ftok = tok2; ftok && ftok->str() != "("; ftok = ftok->previous()) {
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if (ftok->str() == ")")
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ftok = ftok->link();
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else if (ftok->str() == ",")
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argumentNumber++;
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}
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ftok = ftok ? ftok->previous() : nullptr;
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if (!(ftok && ftok->function()))
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return true;
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const Variable *par = ftok->function()->getArgumentVar(argumentNumber);
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if (par == nullptr || par->isReference() || par->isPointer())
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return true;
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}
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if (tok2->str() == "}")
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return false;
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if (Token::Match(tok2, "break|continue|return"))
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ret = true;
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if (ret && tok2->str() == ";")
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return false;
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if (!islocal && Token::Match(tok2, "%var% (") && !Token::simpleMatch(tok2->next()->link(), ") {"))
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return true;
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if (Token::Match(tok2, "if|while (")) {
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if (!islocal && tok2->str() == "while")
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continue;
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// parse condition
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const Token * const end = tok2->next()->link();
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for (; tok2 != end; tok2 = tok2->next()) {
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if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid)) {
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return true;
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}
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if (Token::Match(tok2,"&&|%oror%|( %varid% %any% %num% &&|%oror%|)", varid)) {
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const Token *vartok = tok2->next();
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const std::string& op(vartok->strAt(1));
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const MathLib::bigint num2 = MathLib::toLongNumber(vartok->strAt(2));
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const std::string condition(vartok->str() + op + vartok->strAt(2));
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if (op == "==" && (num & num2) != ((bitop=='&') ? num2 : num))
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assignIfError(assignTok, tok2, condition, false);
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else if (op == "!=" && (num & num2) != ((bitop=='&') ? num2 : num))
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assignIfError(assignTok, tok2, condition, true);
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}
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}
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bool ret1 = assignIfParseScope(assignTok, end->tokAt(2), varid, islocal, bitop, num);
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bool ret2 = false;
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if (Token::simpleMatch(end->next()->link(), "} else {"))
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ret2 = assignIfParseScope(assignTok, end->next()->link()->tokAt(3), varid, islocal, bitop, num);
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if (ret1 || ret2)
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return true;
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}
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}
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return false;
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}
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void CheckAssignIf::assignIfError(const Token *tok1, const Token *tok2, const std::string &condition, bool result)
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{
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std::list<const Token *> locations;
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locations.push_back(tok1);
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locations.push_back(tok2);
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reportError(locations,
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Severity::style,
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"assignIfError",
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"Mismatching assignment and comparison, comparison '" + condition + "' is always " + std::string(result ? "true" : "false") + ".");
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}
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void CheckAssignIf::mismatchingBitAndError(const Token *tok1, const MathLib::bigint num1, const Token *tok2, const MathLib::bigint num2)
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{
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std::list<const Token *> locations;
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locations.push_back(tok1);
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locations.push_back(tok2);
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std::ostringstream msg;
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msg << "Mismatching bitmasks. Result is always 0 ("
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<< "X = Y & 0x" << std::hex << num1 << "; Z = X & 0x" << std::hex << num2 << "; => Z=0).";
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reportError(locations,
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Severity::style,
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"mismatchingBitAnd",
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msg.str());
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}
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static void getnumchildren(const Token *tok, std::list<MathLib::bigint> &numchildren)
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{
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if (tok->astOperand1() && tok->astOperand1()->isNumber())
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numchildren.push_back(MathLib::toLongNumber(tok->astOperand1()->str()));
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else if (tok->astOperand1() && tok->str() == tok->astOperand1()->str())
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getnumchildren(tok->astOperand1(), numchildren);
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if (tok->astOperand2() && tok->astOperand2()->isNumber())
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numchildren.push_back(MathLib::toLongNumber(tok->astOperand2()->str()));
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else if (tok->astOperand2() && tok->str() == tok->astOperand2()->str())
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getnumchildren(tok->astOperand2(), numchildren);
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}
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void CheckAssignIf::comparison()
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{
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if (!_settings->isEnabled("style"))
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return;
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// Experimental code based on AST
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
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if (Token::Match(tok, "==|!=")) {
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const Token *expr1 = tok->astOperand1();
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const Token *expr2 = tok->astOperand2();
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if (!expr1 || !expr2)
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continue;
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if (expr1->isNumber())
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std::swap(expr1,expr2);
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if (!expr2->isNumber())
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continue;
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const MathLib::bigint num2 = MathLib::toLongNumber(expr2->str());
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if (num2 < 0)
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continue;
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if (!Token::Match(expr1,"[&|]"))
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continue;
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std::list<MathLib::bigint> numbers;
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getnumchildren(expr1, numbers);
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for (std::list<MathLib::bigint>::const_iterator num = numbers.begin(); num != numbers.end(); ++num) {
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const MathLib::bigint num1 = *num;
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if (num1 < 0)
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continue;
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if ((expr1->str() == "&" && (num1 & num2) != num2) ||
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(expr1->str() == "|" && (num1 | num2) != num2)) {
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const std::string& op(tok->str());
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comparisonError(expr1, expr1->str(), num1, op, num2, op=="==" ? false : true);
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}
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}
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}
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}
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}
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void CheckAssignIf::comparisonError(const Token *tok, const std::string &bitop, MathLib::bigint value1, const std::string &op, MathLib::bigint value2, bool result)
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{
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std::ostringstream expression;
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expression << std::hex << "(X " << bitop << " 0x" << value1 << ") " << op << " 0x" << value2;
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const std::string errmsg("Expression '" + expression.str() + "' is always " + (result?"true":"false") + ".\n"
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"The expression '" + expression.str() + "' is always " + (result?"true":"false") +
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". Check carefully constants and operators used, these errors might be hard to "
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"spot sometimes. In case of complex expression it might help to split it to "
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"separate expressions.");
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reportError(tok, Severity::style, "comparisonError", errmsg);
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}
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extern bool isSameExpression(const Token *tok1, const Token *tok2, const std::set<std::string> &constFunctions);
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static bool isOverlappingCond(const Token * const cond1, const Token * const cond2, const std::set<std::string> &constFunctions)
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{
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if (!cond1 || !cond2)
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return false;
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// same expressions
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if (isSameExpression(cond1,cond2,constFunctions))
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return true;
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// bitwise overlap for example 'x&7' and 'x==1'
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if (cond1->str() == "&" && cond1->astOperand1() && cond2->astOperand2()) {
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const Token *expr1 = cond1->astOperand1();
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const Token *num1 = cond1->astOperand2();
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if (!num1) // unary operator&
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return false;
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if (!num1->isNumber())
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std::swap(expr1,num1);
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if (!num1->isNumber() || MathLib::isNegative(num1->str()))
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return false;
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if (!Token::Match(cond2, "&|==") || !cond2->astOperand1() || !cond2->astOperand2())
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return false;
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const Token *expr2 = cond2->astOperand1();
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const Token *num2 = cond2->astOperand2();
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if (!num2->isNumber())
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std::swap(expr2,num2);
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if (!num2->isNumber() || MathLib::isNegative(num2->str()))
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return false;
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if (!isSameExpression(expr1,expr2,constFunctions))
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return false;
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const MathLib::bigint value1 = MathLib::toLongNumber(num1->str());
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const MathLib::bigint value2 = MathLib::toLongNumber(num2->str());
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return ((value1 & value2) == value2);
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}
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return false;
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}
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void CheckAssignIf::multiCondition()
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{
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if (!_settings->isEnabled("style"))
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return;
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const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
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for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
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if (i->type != Scope::eIf || !Token::simpleMatch(i->classDef, "if ("))
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continue;
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const Token * const cond1 = i->classDef->next()->astOperand2();
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const Token * tok2 = i->classDef->next();
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while (tok2) {
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tok2 = tok2->link();
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if (!Token::simpleMatch(tok2, ") {"))
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break;
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tok2 = tok2->linkAt(1);
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if (!Token::simpleMatch(tok2, "} else { if ("))
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break;
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tok2 = tok2->tokAt(4);
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if (isOverlappingCond(cond1, tok2->astOperand2(), _settings->library.functionpure))
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multiConditionError(tok2, cond1->linenr());
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}
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}
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}
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void CheckAssignIf::multiConditionError(const Token *tok, unsigned int line1)
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{
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std::ostringstream errmsg;
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errmsg << "Expression is always false because 'else if' condition matches previous condition at line "
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<< line1 << ".";
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reportError(tok, Severity::style, "multiCondition", errmsg.str());
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}
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