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checkother.cpp
2877 lines (2573 loc) · 137 KB
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checkother.cpp
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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2018 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 <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
#include "checkother.h"
#include "astutils.h"
#include "errorlogger.h"
#include "library.h"
#include "mathlib.h"
#include "settings.h"
#include "standards.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"
#include "utils.h"
#include <algorithm> // find_if()
#include <list>
#include <map>
#include <ostream>
#include <set>
#include <stack>
#include <utility>
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckOther instance;
}
static const struct CWE CWE128(128U); // Wrap-around Error
static const struct CWE CWE131(131U); // Incorrect Calculation of Buffer Size
static const struct CWE CWE197(197U); // Numeric Truncation Error
static const struct CWE CWE362(362U); // Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
static const struct CWE CWE369(369U); // Divide By Zero
static const struct CWE CWE398(398U); // Indicator of Poor Code Quality
static const struct CWE CWE475(475U); // Undefined Behavior for Input to API
static const struct CWE CWE482(482U); // Comparing instead of Assigning
static const struct CWE CWE561(561U); // Dead Code
static const struct CWE CWE563(563U); // Assignment to Variable without Use ('Unused Variable')
static const struct CWE CWE570(570U); // Expression is Always False
static const struct CWE CWE571(571U); // Expression is Always True
static const struct CWE CWE672(672U); // Operation on a Resource after Expiration or Release
static const struct CWE CWE628(628U); // Function Call with Incorrectly Specified Arguments
static const struct CWE CWE683(683U); // Function Call With Incorrect Order of Arguments
static const struct CWE CWE686(686U); // Function Call With Incorrect Argument Type
static const struct CWE CWE704(704U); // Incorrect Type Conversion or Cast
static const struct CWE CWE758(758U); // Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
static const struct CWE CWE768(768U); // Incorrect Short Circuit Evaluation
static const struct CWE CWE783(783U); // Operator Precedence Logic Error
//----------------------------------------------------------------------------------
// The return value of fgetc(), getc(), ungetc(), getchar() etc. is an integer value.
// If this return value is stored in a character variable and then compared
// to EOF, which is an integer, the comparison maybe be false.
//
// Reference:
// - Ticket #160
// - http://www.cplusplus.com/reference/cstdio/fgetc/
// - http://www.cplusplus.com/reference/cstdio/getc/
// - http://www.cplusplus.com/reference/cstdio/getchar/
// - http://www.cplusplus.com/reference/cstdio/ungetc/ ...
//----------------------------------------------------------------------------------
void CheckOther::checkCastIntToCharAndBack()
{
if (!_settings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
std::map<unsigned int, std::string> vars;
for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
// Quick check to see if any of the matches below have any chances
if (!Token::Match(tok, "%var%|EOF %comp%|="))
continue;
if (Token::Match(tok, "%var% = fclose|fflush|fputc|fputs|fscanf|getchar|getc|fgetc|putchar|putc|puts|scanf|sscanf|ungetc (")) {
const Variable *var = tok->variable();
if (var && var->typeEndToken()->str() == "char" && !var->typeEndToken()->isSigned()) {
vars[tok->varId()] = tok->strAt(2);
}
} else if (Token::Match(tok, "EOF %comp% ( %var% = fclose|fflush|fputc|fputs|fscanf|getchar|getc|fgetc|putchar|putc|puts|scanf|sscanf|ungetc (")) {
tok = tok->tokAt(3);
const Variable *var = tok->variable();
if (var && var->typeEndToken()->str() == "char" && !var->typeEndToken()->isSigned()) {
checkCastIntToCharAndBackError(tok, tok->strAt(2));
}
} else if (_tokenizer->isCPP() && (Token::Match(tok, "EOF %comp% ( %var% = std :: cin . get (") || Token::Match(tok, "EOF %comp% ( %var% = cin . get ("))) {
tok = tok->tokAt(3);
const Variable *var = tok->variable();
if (var && var->typeEndToken()->str() == "char" && !var->typeEndToken()->isSigned()) {
checkCastIntToCharAndBackError(tok, "cin.get");
}
} else if (_tokenizer->isCPP() && (Token::Match(tok, "%var% = std :: cin . get (") || Token::Match(tok, "%var% = cin . get ("))) {
const Variable *var = tok->variable();
if (var && var->typeEndToken()->str() == "char" && !var->typeEndToken()->isSigned()) {
vars[tok->varId()] = "cin.get";
}
} else if (Token::Match(tok, "%var% %comp% EOF")) {
if (vars.find(tok->varId()) != vars.end()) {
checkCastIntToCharAndBackError(tok, vars[tok->varId()]);
}
} else if (Token::Match(tok, "EOF %comp% %var%")) {
tok = tok->tokAt(2);
if (vars.find(tok->varId()) != vars.end()) {
checkCastIntToCharAndBackError(tok, vars[tok->varId()]);
}
}
}
}
}
void CheckOther::checkCastIntToCharAndBackError(const Token *tok, const std::string &strFunctionName)
{
reportError(
tok,
Severity::warning,
"checkCastIntToCharAndBack",
"$symbol:" + strFunctionName + "\n"
"Storing $symbol() return value in char variable and then comparing with EOF.\n"
"When saving $symbol() return value in char variable there is loss of precision. "
" When $symnol() returns EOF this value is truncated. Comparing the char "
"variable with EOF can have unexpected results. For instance a loop \"while (EOF != (c = $symbol());\" "
"loops forever on some compilers/platforms and on other compilers/platforms it will stop "
"when the file contains a matching character.", CWE197, false
);
}
//---------------------------------------------------------------------------
// Clarify calculation precedence for ternary operators.
//---------------------------------------------------------------------------
void CheckOther::clarifyCalculation()
{
if (!_settings->isEnabled(Settings::STYLE))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
// ? operator where lhs is arithmetical expression
if (tok->str() != "?" || !tok->astOperand1() || !tok->astOperand1()->isCalculation())
continue;
if (!tok->astOperand1()->isArithmeticalOp() && tok->astOperand1()->tokType() != Token::eBitOp)
continue;
// Is code clarified by parentheses already?
const Token *tok2 = tok->astOperand1();
for (; tok2; tok2 = tok2->next()) {
if (tok2->str() == "(")
tok2 = tok2->link();
else if (tok2->str() == ")")
break;
else if (tok2->str() == "?") {
clarifyCalculationError(tok, tok->astOperand1()->str());
break;
}
}
}
}
}
void CheckOther::clarifyCalculationError(const Token *tok, const std::string &op)
{
// suspicious calculation
const std::string calc("'a" + op + "b?c:d'");
// recommended calculation #1
const std::string s1("'(a" + op + "b)?c:d'");
// recommended calculation #2
const std::string s2("'a" + op + "(b?c:d)'");
reportError(tok,
Severity::style,
"clarifyCalculation",
"Clarify calculation precedence for '" + op + "' and '?'.\n"
"Suspicious calculation. Please use parentheses to clarify the code. "
"The code '" + calc + "' should be written as either '" + s1 + "' or '" + s2 + "'.", CWE783, false);
}
//---------------------------------------------------------------------------
// Clarify (meaningless) statements like *foo++; with parentheses.
//---------------------------------------------------------------------------
void CheckOther::clarifyStatement()
{
if (!_settings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart; tok && tok != scope->bodyEnd; tok = tok->next()) {
if (Token::Match(tok, "* %name%") && tok->astOperand1()) {
const Token *tok2 = tok->previous();
while (tok2 && tok2->str() == "*")
tok2 = tok2->previous();
if (tok2 && !tok2->astParent() && Token::Match(tok2, "[{};]")) {
tok2 = tok->astOperand1();
if (Token::Match(tok2, "++|-- [;,]"))
clarifyStatementError(tok2);
}
}
}
}
}
void CheckOther::clarifyStatementError(const Token *tok)
{
reportError(tok, Severity::warning, "clarifyStatement", "Ineffective statement similar to '*A++;'. Did you intend to write '(*A)++;'?\n"
"A statement like '*A++;' might not do what you intended. Postfix 'operator++' is executed before 'operator*'. "
"Thus, the dereference is meaningless. Did you intend to write '(*A)++;'?", CWE783, false);
}
//---------------------------------------------------------------------------
// Check for suspicious occurrences of 'if(); {}'.
//---------------------------------------------------------------------------
void CheckOther::checkSuspiciousSemicolon()
{
if (!_settings->inconclusive || !_settings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
// Look for "if(); {}", "for(); {}" or "while(); {}"
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
if (i->type == Scope::eIf || i->type == Scope::eElse || i->type == Scope::eWhile || i->type == Scope::eFor) {
// Ensure the semicolon is at the same line number as the if/for/while statement
// and the {..} block follows it without an extra empty line.
if (Token::simpleMatch(i->bodyStart, "{ ; } {") &&
i->bodyStart->previous()->linenr() == i->bodyStart->tokAt(2)->linenr()
&& i->bodyStart->linenr()+1 >= i->bodyStart->tokAt(3)->linenr()) {
SuspiciousSemicolonError(i->classDef);
}
}
}
}
void CheckOther::SuspiciousSemicolonError(const Token* tok)
{
reportError(tok, Severity::warning, "suspiciousSemicolon",
"Suspicious use of ; at the end of '" + (tok ? tok->str() : std::string()) + "' statement.", CWE398, true);
}
//---------------------------------------------------------------------------
// For C++ code, warn if C-style casts are used on pointer types
//---------------------------------------------------------------------------
void CheckOther::warningOldStylePointerCast()
{
// Only valid on C++ code
if (!_settings->isEnabled(Settings::STYLE) || !_tokenizer->isCPP())
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
const Token* tok;
if (scope->function && scope->function->isConstructor())
tok = scope->classDef;
else
tok = scope->bodyStart;
for (; tok && tok != scope->bodyEnd; tok = tok->next()) {
// Old style pointer casting..
if (!Token::Match(tok, "( const|volatile| const|volatile| %type% * const| ) (| %name%|%num%|%bool%|%char%|%str%"))
continue;
// skip first "const" in "const Type* const"
while (Token::Match(tok->next(), "const|volatile"))
tok = tok->next();
const Token* typeTok = tok->next();
// skip second "const" in "const Type* const"
if (tok->strAt(3) == "const")
tok = tok->next();
const Token *p = tok->tokAt(4);
if (p->hasKnownIntValue() && p->values().front().intvalue==0) // Casting nullpointers is safe
continue;
// Is "type" a class?
if (typeTok->type())
cstyleCastError(tok);
}
}
}
void CheckOther::cstyleCastError(const Token *tok)
{
reportError(tok, Severity::style, "cstyleCast",
"C-style pointer casting\n"
"C-style pointer casting detected. C++ offers four different kinds of casts as replacements: "
"static_cast, const_cast, dynamic_cast and reinterpret_cast. A C-style cast could evaluate to "
"any of those automatically, thus it is considered safer if the programmer explicitly states "
"which kind of cast is expected. See also: https://www.securecoding.cert.org/confluence/display/cplusplus/EXP05-CPP.+Do+not+use+C-style+casts.", CWE398, false);
}
//---------------------------------------------------------------------------
// float* f; double* d = (double*)f; <-- Pointer cast to a type with an incompatible binary data representation
//---------------------------------------------------------------------------
void CheckOther::invalidPointerCast()
{
if (!_settings->isEnabled(Settings::PORTABILITY))
return;
const bool printInconclusive = _settings->inconclusive;
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
const Token* toTok = nullptr;
const Token* fromTok = nullptr;
// Find cast
if (Token::Match(tok, "( const|volatile| const|volatile| %type% %type%| const| * )")) {
toTok = tok;
fromTok = tok->astOperand1();
} else if (Token::simpleMatch(tok, "reinterpret_cast <") && tok->linkAt(1)) {
toTok = tok->linkAt(1)->next();
fromTok = toTok->astOperand2();
}
if (!fromTok)
continue;
const ValueType* fromType = fromTok->valueType();
const ValueType* toType = toTok->valueType();
if (!fromType || !toType || !fromType->pointer || !toType->pointer)
continue;
if (fromType->type != toType->type && fromType->type >= ValueType::Type::BOOL && toType->type >= ValueType::Type::BOOL && (toType->type != ValueType::Type::CHAR || printInconclusive)) {
if (toType->isIntegral() && fromType->isIntegral())
continue;
std::string toStr = toType->isIntegral() ? "integer *" : toType->str();
toStr.erase(toStr.size()-2);
std::string fromStr = fromType->isIntegral() ? "integer *" : fromType->str();
fromStr.erase(fromStr.size() - 2);
invalidPointerCastError(tok, fromStr, toStr, toType->type == ValueType::Type::CHAR);
}
}
}
}
void CheckOther::invalidPointerCastError(const Token* tok, const std::string& from, const std::string& to, bool inconclusive)
{
if (to == "integer") { // If we cast something to int*, this can be useful to play with its binary data representation
if (!inconclusive)
reportError(tok, Severity::portability, "invalidPointerCast", "Casting from " + from + "* to integer* is not portable due to different binary data representations on different platforms.", CWE704, false);
else
reportError(tok, Severity::portability, "invalidPointerCast", "Casting from " + from + "* to char* is not portable due to different binary data representations on different platforms.", CWE704, true);
} else
reportError(tok, Severity::portability, "invalidPointerCast", "Casting between " + from + "* and " + to + "* which have an incompatible binary data representation.", CWE704, false);
}
//---------------------------------------------------------------------------
// This check detects errors on POSIX systems, when a pipe command called
// with a wrong dimensioned file descriptor array. The pipe command requires
// exactly an integer array of dimension two as parameter.
//
// References:
// - http://linux.die.net/man/2/pipe
// - ticket #3521
//---------------------------------------------------------------------------
void CheckOther::checkPipeParameterSize()
{
if (!_settings->standards.posix)
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
if (Token::Match(tok, "pipe ( %var% )") ||
Token::Match(tok, "pipe2 ( %var% ,")) {
const Token * const varTok = tok->tokAt(2);
const Variable *var = varTok->variable();
MathLib::bigint dim;
if (var && var->isArray() && !var->isArgument() && ((dim=var->dimension(0U)) < 2)) {
const std::string strDim = MathLib::toString(dim);
checkPipeParameterSizeError(varTok,varTok->str(), strDim);
}
}
}
}
}
void CheckOther::checkPipeParameterSizeError(const Token *tok, const std::string &strVarName, const std::string &strDim)
{
reportError(tok, Severity::error,
"wrongPipeParameterSize",
"$symbol:" + strVarName + "\n"
"Buffer '$symbol' must have size of 2 integers if used as parameter of pipe().\n"
"The pipe()/pipe2() system command takes an argument, which is an array of exactly two integers.\n"
"The variable '$symbol' is an array of size " + strDim + ", which does not match.", CWE686, false);
}
//---------------------------------------------------------------------------
// Detect redundant assignments: x = 0; x = 4;
//---------------------------------------------------------------------------
static bool nonLocal(const Variable* var)
{
return !var || (!var->isLocal() && !var->isArgument()) || var->isStatic() || var->isReference();
}
static bool nonLocalVolatile(const Variable* var)
{
if (var && var->isVolatile())
return false;
return nonLocal(var);
}
static void eraseNotLocalArg(std::map<unsigned int, const Token*>& container, const SymbolDatabase* symbolDatabase)
{
for (std::map<unsigned int, const Token*>::iterator i = container.begin(); i != container.end();) {
const Variable* var = symbolDatabase->getVariableFromVarId(i->first);
if (!var || nonLocal(var)) {
container.erase(i++);
} else
++i;
}
}
static void eraseMemberAssignments(const unsigned int varId, const std::map<unsigned int, std::set<unsigned int> > &membervars, std::map<unsigned int, const Token*> &varAssignments)
{
const std::map<unsigned int, std::set<unsigned int> >::const_iterator it = membervars.find(varId);
if (it != membervars.end()) {
const std::set<unsigned int>& v = it->second;
for (std::set<unsigned int>::const_iterator vit = v.begin(); vit != v.end(); ++vit) {
varAssignments.erase(*vit);
if (*vit != varId)
eraseMemberAssignments(*vit, membervars, varAssignments);
}
}
}
static bool checkExceptionHandling(const Token* tok)
{
const Variable* var = tok->variable();
const Scope* upperScope = tok->scope();
if (var && upperScope == var->scope())
return true;
while (upperScope && upperScope->type != Scope::eTry && upperScope->type != Scope::eLambda && (!var || upperScope->nestedIn != var->scope()) && upperScope->isExecutable()) {
upperScope = upperScope->nestedIn;
}
if (var && upperScope && upperScope->type == Scope::eTry) {
// Check all exception han
const Token* tok2 = upperScope->bodyEnd;
while (Token::simpleMatch(tok2, "} catch (")) {
tok2 = tok2->linkAt(2)->next();
if (Token::findmatch(tok2, "%varid%", tok2->link(), var->declarationId()))
return false;
tok2 = tok2->link();
}
}
return true;
}
void CheckOther::checkRedundantAssignment()
{
const bool printPerformance = _settings->isEnabled(Settings::PERFORMANCE);
const bool printStyle = _settings->isEnabled(Settings::STYLE);
const bool printWarning = _settings->isEnabled(Settings::WARNING);
if (!printWarning && !printPerformance && !printStyle)
return;
const bool printInconclusive = _settings->inconclusive;
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
for (std::list<Scope>::const_iterator scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope) {
if (!scope->isExecutable())
continue;
std::map<unsigned int, const Token*> varAssignments;
std::map<unsigned int, const Token*> memAssignments;
std::map<unsigned int, std::set<unsigned int> > membervars;
std::set<unsigned int> initialized;
const Token* writtenArgumentsEnd = nullptr;
for (const Token* tok = scope->bodyStart->next(); tok && tok != scope->bodyEnd; tok = tok->next()) {
if (tok == writtenArgumentsEnd)
writtenArgumentsEnd = nullptr;
if (tok->str() == "?" && tok->astOperand2()) {
tok = Token::findmatch(tok->astOperand2(), ";|}");
if (!tok)
break;
varAssignments.clear();
memAssignments.clear();
} else if (tok->str() == "{" && tok->strAt(-1) != "{" && tok->strAt(-1) != "=" && tok->strAt(-4) != "case" && tok->strAt(-3) != "default") { // conditional or non-executable inner scope: Skip it and reset status
tok = tok->link();
varAssignments.clear();
memAssignments.clear();
} else if (Token::Match(tok, "for|if|while (")) {
tok = tok->linkAt(1);
} else if (Token::Match(tok, "break|return|continue|throw|goto|asm")) {
varAssignments.clear();
memAssignments.clear();
} else if (tok->tokType() == Token::eVariable && !Token::Match(tok, "%name% (")) {
const Token *eq = nullptr;
for (const Token *tok2 = tok; tok2; tok2 = tok2->next()) {
if (Token::Match(tok2, "[([]")) {
// bail out if there is a variable in rhs - we only track 1 variable
bool bailout = false;
for (const Token *tok3 = tok2->link(); tok3 != tok2; tok3 = tok3->previous()) {
if (tok3->varId()) {
const Variable *var = tok3->variable();
if (!var || !var->isConst() || var->isReference() || var->isPointer()) {
bailout = true;
break;
}
}
}
if (bailout)
break;
tok2 = tok2->link();
} else if (Token::Match(tok2, "[)];,]"))
break;
else if (tok2->str() == "=") {
eq = tok2;
break;
}
}
// Set initialization flag
if (!Token::Match(tok, "%var% ["))
initialized.insert(tok->varId());
else {
const Token *tok2 = tok->next();
while (tok2 && tok2->str() == "[")
tok2 = tok2->link()->next();
if (tok2 && tok2->str() != ";")
initialized.insert(tok->varId());
}
const Token *startToken = tok;
while (Token::Match(startToken, "%name%|::|.")) {
startToken = startToken->previous();
if (Token::Match(startToken, "%name% . %var%"))
membervars[startToken->varId()].insert(startToken->tokAt(2)->varId());
}
const std::map<unsigned int, const Token*>::iterator it = varAssignments.find(tok->varId());
if (eq && Token::Match(startToken, "[;{}]")) { // Assignment
if (it != varAssignments.end()) {
const Token *oldeq = nullptr;
for (const Token *tok2 = it->second; tok2; tok2 = tok2->next()) {
if (Token::Match(tok2, "[([]"))
tok2 = tok2->link();
else if (Token::Match(tok2, "[)];,]"))
break;
else if (Token::Match(tok2, "++|--|=")) {
oldeq = tok2;
break;
}
}
if (!oldeq) {
const Token *tok2 = it->second;
while (Token::Match(tok2, "%name%|.|[|*|("))
tok2 = tok2->astParent();
if (Token::Match(tok2, "++|--"))
oldeq = tok2;
}
// Ensure that LHS in assignments are the same
bool error = oldeq && eq->astOperand1() && isSameExpression(_tokenizer->isCPP(), true, eq->astOperand1(), oldeq->astOperand1(), _settings->library, true);
// Ensure that variable is not used on right side
std::stack<const Token *> tokens;
tokens.push(eq->astOperand2());
while (!tokens.empty()) {
const Token *rhs = tokens.top();
tokens.pop();
if (!rhs)
continue;
tokens.push(rhs->astOperand1());
tokens.push(rhs->astOperand2());
if (rhs->varId() == tok->varId()) {
error = false;
break;
}
if (Token::Match(rhs->previous(), "%name% (") && nonLocalVolatile(tok->variable())) { // Called function might use the variable
const Function* const func = rhs->function();
const Variable* const var = tok->variable();
if (!var || var->isGlobal() || var->isReference() || ((!func || func->nestedIn) && rhs->strAt(-1) != ".")) {// Global variable, or member function
error = false;
break;
}
}
}
if (error) {
if (printWarning && scope->type == Scope::eSwitch && Token::findmatch(it->second, "default|case", tok))
redundantAssignmentInSwitchError(it->second, tok, eq->astOperand1()->expressionString());
else if (printStyle) {
// c++, unknown type => assignment might have additional side effects
const bool possibleSideEffects(_tokenizer->isCPP() && !tok->valueType());
// TODO nonlocal variables are not tracked entirely.
const bool nonlocal = it->second->variable() && nonLocalVolatile(it->second->variable());
// Warnings are inconclusive if there are possible side effects or if variable is not
// tracked perfectly.
const bool inconclusive = possibleSideEffects | nonlocal;
if (printInconclusive || !inconclusive)
if (_tokenizer->isC() || checkExceptionHandling(tok)) // see #6555 to see how exception handling might have an impact
redundantAssignmentError(it->second, tok, eq->astOperand1()->expressionString(), inconclusive);
}
}
it->second = tok;
}
if (!Token::simpleMatch(tok->tokAt(2), "0 ;") || (tok->variable() && tok->variable()->nameToken() != tok->tokAt(-2)))
varAssignments[tok->varId()] = tok;
memAssignments.erase(tok->varId());
eraseMemberAssignments(tok->varId(), membervars, varAssignments);
} else if ((tok->next() && tok->next()->tokType() == Token::eIncDecOp) || (tok->previous()->tokType() == Token::eIncDecOp && tok->strAt(1) == ";")) { // Variable incremented/decremented; Prefix-Increment is only suspicious, if its return value is unused
varAssignments[tok->varId()] = tok;
memAssignments.erase(tok->varId());
eraseMemberAssignments(tok->varId(), membervars, varAssignments);
} else if (!Token::simpleMatch(tok->tokAt(-2), "sizeof (")) { // Other usage of variable
if (it != varAssignments.end())
varAssignments.erase(it);
if (!writtenArgumentsEnd) // Indicates that we are in the first argument of strcpy/memcpy/... function
memAssignments.erase(tok->varId());
}
} else if (Token::Match(tok, "%name% (") && !_settings->library.isFunctionConst(tok->str(), true)) { // Function call. Global variables might be used. Reset their status
const bool memfunc = Token::Match(tok, "memcpy|memmove|memset|strcpy|strncpy|sprintf|snprintf|strcat|strncat|wcscpy|wcsncpy|swprintf|wcscat|wcsncat");
if (tok->varId()) // operator() or function pointer
varAssignments.erase(tok->varId());
if (memfunc && tok->strAt(-1) != "(" && tok->strAt(-1) != "=") {
const Token* param1 = tok->tokAt(2);
writtenArgumentsEnd = param1->next();
if (param1->varId() && param1->strAt(1) == "," && !Token::Match(tok, "strcat|strncat|wcscat|wcsncat") && param1->variable() && param1->variable()->isLocal() && param1->variable()->isArray()) {
if (tok->str() == "memset" && initialized.find(param1->varId()) == initialized.end())
initialized.insert(param1->varId());
else {
const std::map<unsigned int, const Token*>::const_iterator it = memAssignments.find(param1->varId());
if (it == memAssignments.end())
memAssignments[param1->varId()] = tok;
else {
bool read = false;
for (const Token *tok2 = tok->linkAt(1); tok2 != writtenArgumentsEnd; tok2 = tok2->previous()) {
if (tok2->varId() == param1->varId()) {
// TODO: is this a read? maybe it's a write
read = true;
break;
}
}
if (read) {
memAssignments[param1->varId()] = tok;
continue;
}
if (printWarning && scope->type == Scope::eSwitch && Token::findmatch(it->second, "default|case", tok))
redundantCopyInSwitchError(it->second, tok, param1->str());
else if (printPerformance)
redundantCopyError(it->second, tok, param1->str());
}
}
}
} else if (scope->type == Scope::eSwitch) { // Avoid false positives if noreturn function is called in switch
const Function* const func = tok->function();
if (!func || !func->hasBody()) {
varAssignments.clear();
memAssignments.clear();
continue;
}
const Token* funcEnd = func->functionScope->bodyEnd;
bool noreturn;
if (!_tokenizer->IsScopeNoReturn(funcEnd, &noreturn) && !noreturn) {
eraseNotLocalArg(varAssignments, symbolDatabase);
eraseNotLocalArg(memAssignments, symbolDatabase);
} else {
varAssignments.clear();
memAssignments.clear();
}
} else { // Noreturn functions outside switch don't cause problems
eraseNotLocalArg(varAssignments, symbolDatabase);
eraseNotLocalArg(memAssignments, symbolDatabase);
}
}
}
}
}
void CheckOther::redundantCopyError(const Token *tok1, const Token* tok2, const std::string& var)
{
const std::list<const Token *> callstack = { tok1, tok2 };
reportError(callstack, Severity::performance, "redundantCopy",
"$symbol:" + var + "\n"
"Buffer '$symbol' is being written before its old content has been used.", CWE563, false);
}
void CheckOther::redundantCopyInSwitchError(const Token *tok1, const Token* tok2, const std::string &var)
{
const std::list<const Token *> callstack = { tok1, tok2 };
reportError(callstack, Severity::warning, "redundantCopyInSwitch",
"$symbol:" + var + "\n"
"Buffer '$symbol' is being written before its old content has been used. 'break;' missing?", CWE563, false);
}
void CheckOther::redundantAssignmentError(const Token *tok1, const Token* tok2, const std::string& var, bool inconclusive)
{
const std::list<const Token *> callstack = { tok1, tok2 };
if (inconclusive)
reportError(callstack, Severity::style, "redundantAssignment",
"$symbol:" + var + "\n"
"Variable '$symbol' is reassigned a value before the old one has been used if variable is no semaphore variable.\n"
"Variable '$symbol' is reassigned a value before the old one has been used. Make sure that this variable is not used like a semaphore in a threading environment before simplifying this code.", CWE563, true);
else
reportError(callstack, Severity::style, "redundantAssignment",
"$symbol:" + var + "\n"
"Variable '$symbol' is reassigned a value before the old one has been used.", CWE563, false);
}
void CheckOther::redundantAssignmentInSwitchError(const Token *tok1, const Token* tok2, const std::string &var)
{
const std::list<const Token *> callstack = { tok1, tok2 };
reportError(callstack, Severity::warning, "redundantAssignInSwitch",
"$symbol:" + var + "\n"
"Variable '$symbol' is reassigned a value before the old one has been used. 'break;' missing?", CWE563, false);
}
//---------------------------------------------------------------------------
// switch (x)
// {
// case 2:
// y = a; // <- this assignment is redundant
// case 3:
// y = b; // <- case 2 falls through and sets y twice
// }
//---------------------------------------------------------------------------
static inline bool isFunctionOrBreakPattern(const Token *tok)
{
if (Token::Match(tok, "%name% (") || Token::Match(tok, "break|continue|return|exit|goto|throw"))
return true;
return false;
}
void CheckOther::checkRedundantAssignmentInSwitch()
{
if (!_settings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
// Find the beginning of a switch. E.g.:
// switch (var) { ...
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
if (i->type != Scope::eSwitch || !i->bodyStart)
continue;
// Check the contents of the switch statement
std::map<unsigned int, const Token*> varsWithBitsSet;
std::map<unsigned int, std::string> bitOperations;
for (const Token *tok2 = i->bodyStart->next(); tok2 != i->bodyEnd; tok2 = tok2->next()) {
if (tok2->str() == "{") {
// Inside a conditional or loop. Don't mark variable accesses as being redundant. E.g.:
// case 3: b = 1;
// case 4: if (a) { b = 2; } // Doesn't make the b=1 redundant because it's conditional
if (Token::Match(tok2->previous(), ")|else {") && tok2->link()) {
const Token* endOfConditional = tok2->link();
for (const Token* tok3 = tok2; tok3 != endOfConditional; tok3 = tok3->next()) {
if (tok3->varId() != 0) {
varsWithBitsSet.erase(tok3->varId());
bitOperations.erase(tok3->varId());
} else if (isFunctionOrBreakPattern(tok3)) {
varsWithBitsSet.clear();
bitOperations.clear();
}
}
tok2 = endOfConditional;
}
}
// Variable assignment. Report an error if it's assigned to twice before a break. E.g.:
// case 3: b = 1; // <== redundant
// case 4: b = 2;
if (Token::Match(tok2->previous(), ";|{|}|: %var% = %any% ;")) {
varsWithBitsSet.erase(tok2->varId());
bitOperations.erase(tok2->varId());
}
// Bitwise operation. Report an error if it's performed twice before a break. E.g.:
// case 3: b |= 1; // <== redundant
// case 4: b |= 1;
else if (Token::Match(tok2->previous(), ";|{|}|: %var% %assign% %num% ;") &&
(tok2->strAt(1) == "|=" || tok2->strAt(1) == "&=") &&
Token::Match(tok2->next()->astOperand2(), "%num%")) {
const std::string bitOp = tok2->strAt(1)[0] + tok2->strAt(2);
const std::map<unsigned int, const Token*>::const_iterator i2 = varsWithBitsSet.find(tok2->varId());
// This variable has not had a bit operation performed on it yet, so just make a note of it
if (i2 == varsWithBitsSet.end()) {
varsWithBitsSet[tok2->varId()] = tok2;
bitOperations[tok2->varId()] = bitOp;
}
// The same bit operation has been performed on the same variable twice, so report an error
else if (bitOperations[tok2->varId()] == bitOp)
redundantBitwiseOperationInSwitchError(i2->second, i2->second->str());
// A different bit operation was performed on the variable, so clear it
else {
varsWithBitsSet.erase(tok2->varId());
bitOperations.erase(tok2->varId());
}
}
// Bitwise operation. Report an error if it's performed twice before a break. E.g.:
// case 3: b = b | 1; // <== redundant
// case 4: b = b | 1;
else if (Token::Match(tok2->previous(), ";|{|}|: %var% = %name% %or%|& %num% ;") &&
tok2->varId() == tok2->tokAt(2)->varId()) {
const std::string bitOp = tok2->strAt(3) + tok2->strAt(4);
const std::map<unsigned int, const Token*>::const_iterator i2 = varsWithBitsSet.find(tok2->varId());
// This variable has not had a bit operation performed on it yet, so just make a note of it
if (i2 == varsWithBitsSet.end()) {
varsWithBitsSet[tok2->varId()] = tok2;
bitOperations[tok2->varId()] = bitOp;
}
// The same bit operation has been performed on the same variable twice, so report an error
else if (bitOperations[tok2->varId()] == bitOp)
redundantBitwiseOperationInSwitchError(i2->second, i2->second->str());
// A different bit operation was performed on the variable, so clear it
else {
varsWithBitsSet.erase(tok2->varId());
bitOperations.erase(tok2->varId());
}
}
// Not a simple assignment so there may be good reason if this variable is assigned to twice. E.g.:
// case 3: b = 1;
// case 4: b++;
else if (tok2->varId() != 0 && tok2->strAt(1) != "|" && tok2->strAt(1) != "&") {
varsWithBitsSet.erase(tok2->varId());
bitOperations.erase(tok2->varId());
}
// Reset our record of assignments if there is a break or function call. E.g.:
// case 3: b = 1; break;
if (isFunctionOrBreakPattern(tok2)) {
varsWithBitsSet.clear();
bitOperations.clear();
}
}
}
}
void CheckOther::redundantBitwiseOperationInSwitchError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::warning,
"redundantBitwiseOperationInSwitch",
"$symbol:" + varname + "\n"
"Redundant bitwise operation on '$symbol' in 'switch' statement. 'break;' missing?");
}
//---------------------------------------------------------------------------
// Check for statements like case A||B: in switch()
//---------------------------------------------------------------------------
void CheckOther::checkSuspiciousCaseInSwitch()
{
if (!_settings->inconclusive || !_settings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope & scope : symbolDatabase->scopeList) {
if (scope.type != Scope::eSwitch)
continue;
for (const Token* tok = scope.bodyStart->next(); tok != scope.bodyEnd; tok = tok->next()) {
if (tok->str() == "case") {
const Token* finding = nullptr;
for (const Token* tok2 = tok->next(); tok2; tok2 = tok2->next()) {
if (tok2->str() == ":")
break;
if (Token::Match(tok2, "[;}{]"))
break;
if (tok2->str() == "?")
finding = nullptr;
else if (Token::Match(tok2, "&&|%oror%"))
finding = tok2;
}
if (finding)
suspiciousCaseInSwitchError(finding, finding->str());
}
}
}
}
void CheckOther::suspiciousCaseInSwitchError(const Token* tok, const std::string& operatorString)
{
reportError(tok, Severity::warning, "suspiciousCase",
"Found suspicious case label in switch(). Operator '" + operatorString + "' probably doesn't work as intended.\n"
"Using an operator like '" + operatorString + "' in a case label is suspicious. Did you intend to use a bitwise operator, multiple case labels or if/else instead?", CWE398, true);
}
//---------------------------------------------------------------------------
// if (x == 1)
// x == 0; // <- suspicious equality comparison.
//---------------------------------------------------------------------------
void CheckOther::checkSuspiciousEqualityComparison()
{
if (!_settings->isEnabled(Settings::WARNING) || !_settings->inconclusive)
return;
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
if (Token::simpleMatch(tok, "for (")) {
const Token* const openParen = tok->next();
const Token* const closeParen = tok->linkAt(1);
// Search for any suspicious equality comparison in the initialization
// or increment-decrement parts of the for() loop.
// For example:
// for (i == 2; i < 10; i++)
// or
// for (i = 0; i < 10; i == a)
if (Token::Match(openParen->next(), "%name% =="))
suspiciousEqualityComparisonError(openParen->tokAt(2));
if (closeParen->strAt(-2) == "==")
suspiciousEqualityComparisonError(closeParen->tokAt(-2));
// Skip over for() loop conditions because "for (;running==1;)"
// is a bit strange, but not necessarily incorrect.
tok = closeParen;
} else if (Token::Match(tok, "[;{}] *| %name% == %any% ;")) {
// Exclude compound statements surrounded by parentheses, such as
// printf("%i\n", ({x==0;}));
// because they may appear as an expression in GNU C/C++.
// See http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
const Token* afterStatement = tok->strAt(1) == "*" ? tok->tokAt(6) : tok->tokAt(5);
if (!Token::simpleMatch(afterStatement, "} )"))
suspiciousEqualityComparisonError(tok->next());
}
}
}
}
void CheckOther::suspiciousEqualityComparisonError(const Token* tok)
{
reportError(tok, Severity::warning, "suspiciousEqualityComparison",
"Found suspicious equality comparison. Did you intend to assign a value instead?", CWE482, true);
}
//---------------------------------------------------------------------------
// Find consecutive return, break, continue, goto or throw statements. e.g.:
// break; break;
// Detect dead code, that follows such a statement. e.g.:
// return(0); foo();
//---------------------------------------------------------------------------
void CheckOther::checkUnreachableCode()
{
if (!_settings->isEnabled(Settings::STYLE))
return;
const bool printInconclusive = _settings->inconclusive;
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart; tok && tok != scope->bodyEnd; tok = tok->next()) {
const Token* secondBreak = nullptr;
const Token* labelName = nullptr;
if (tok->link() && Token::Match(tok, "(|[|<"))
tok = tok->link();
else if (Token::Match(tok, "break|continue ;"))
secondBreak = tok->tokAt(2);
else if (Token::Match(tok, "[;{}:] return|throw")) {
tok = tok->next(); // tok should point to return or throw
for (const Token *tok2 = tok->next(); tok2; tok2 = tok2->next()) {
if (tok2->str() == "(" || tok2->str() == "{")
tok2 = tok2->link();
if (tok2->str() == ";") {