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363 lines (319 loc) · 16.7 KB
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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2015 Daniel Marjamäki and 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 "checkstring.h"
#include "symboldatabase.h"
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckString instance;
}
//---------------------------------------------------------------------------
// Writing string literal is UB
//---------------------------------------------------------------------------
void CheckString::stringLiteralWrite()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (!tok->variable() || !tok->variable()->isPointer())
continue;
const Token *str = tok->getValueTokenMinStrSize();
if (!str)
continue;
if (Token::Match(tok, "%var% [") && Token::simpleMatch(tok->linkAt(1), "] ="))
stringLiteralWriteError(tok, str);
else if (Token::Match(tok->previous(), "* %var% ="))
stringLiteralWriteError(tok, str);
}
}
}
void CheckString::stringLiteralWriteError(const Token *tok, const Token *strValue)
{
std::list<const Token *> callstack;
callstack.push_back(tok);
if (strValue)
callstack.push_back(strValue);
std::string errmsg("Modifying string literal");
if (strValue) {
std::string s = strValue->strValue();
if (s.size() > 15U)
s = s.substr(0,13) + "..";
errmsg += " \"" + s + "\"";
}
errmsg += " directly or indirectly is undefined behaviour.";
reportError(callstack, Severity::error, "stringLiteralWrite", errmsg);
}
//---------------------------------------------------------------------------
// Check for string comparison involving two static strings.
// if(strcmp("00FF00","00FF00")==0) // <- statement is always true
//---------------------------------------------------------------------------
void CheckString::checkAlwaysTrueOrFalseStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
for (const Token* tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (tok->isName() && Token::Match(tok, "memcmp|strncmp|strcmp|stricmp|strverscmp|bcmp|strcmpi|strcasecmp|strncasecmp|strncasecmp_l|strcasecmp_l|wcsncasecmp|wcscasecmp|wmemcmp|wcscmp|wcscasecmp_l|wcsncasecmp_l|wcsncmp|_mbscmp|_memicmp|_memicmp_l|_stricmp|_wcsicmp|_mbsicmp|_stricmp_l|_wcsicmp_l|_mbsicmp_l (")) {
if (Token::Match(tok->tokAt(2), "%str% , %str% ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(4);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(5);
} else if (Token::Match(tok->tokAt(2), "%name% , %name% ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(4);
if (str1 == str2)
alwaysTrueStringVariableCompareError(tok, str1, str2);
tok = tok->tokAt(5);
} else if (Token::Match(tok->tokAt(2), "%name% . c_str ( ) , %name% . c_str ( ) ,|)")) {
const std::string &str1 = tok->strAt(2);
const std::string &str2 = tok->strAt(8);
if (str1 == str2)
alwaysTrueStringVariableCompareError(tok, str1, str2);
tok = tok->tokAt(13);
}
} else if (tok->isName() && Token::Match(tok, "QString :: compare ( %str% , %str% )")) {
const std::string &str1 = tok->strAt(4);
const std::string &str2 = tok->strAt(6);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(7);
} else if (Token::Match(tok, "!!+ %str% ==|!= %str% !!+")) {
const std::string &str1 = tok->strAt(1);
const std::string &str2 = tok->strAt(3);
alwaysTrueFalseStringCompareError(tok, str1, str2);
tok = tok->tokAt(5);
}
if (!tok)
break;
}
}
void CheckString::alwaysTrueFalseStringCompareError(const Token *tok, const std::string& str1, const std::string& str2)
{
const std::size_t stringLen = 10;
const std::string string1 = (str1.size() < stringLen) ? str1 : (str1.substr(0, stringLen-2) + "..");
const std::string string2 = (str2.size() < stringLen) ? str2 : (str2.substr(0, stringLen-2) + "..");
reportError(tok, Severity::warning, "staticStringCompare",
"Unnecessary comparison of static strings.\n"
"The compared strings, '" + string1 + "' and '" + string2 + "', are always " + (str1==str2?"identical":"unequal") + ". "
"Therefore the comparison is unnecessary and looks suspicious.");
}
void CheckString::alwaysTrueStringVariableCompareError(const Token *tok, const std::string& str1, const std::string& str2)
{
reportError(tok, Severity::warning, "stringCompare",
"Comparison of identical string variables.\n"
"The compared strings, '" + str1 + "' and '" + str2 + "', are identical. "
"This could be a logic bug.");
}
//-----------------------------------------------------------------------------
// Detect "str == '\0'" where "*str == '\0'" is correct.
// Comparing char* with each other instead of using strcmp()
//-----------------------------------------------------------------------------
void CheckString::checkSuspiciousStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (tok->tokType() != Token::eComparisonOp)
continue;
const Token* varTok = tok->astOperand1();
const Token* litTok = tok->astOperand2();
if (!varTok || !litTok) // <- failed to create AST for comparison
continue;
if (varTok->tokType() == Token::eString || varTok->tokType() == Token::eNumber)
std::swap(varTok, litTok);
else if (litTok->tokType() != Token::eString && litTok->tokType() != Token::eNumber)
continue;
// Pointer addition?
if (varTok->str() == "+" && _tokenizer->isC()) {
const Token *tokens[2] = { varTok->astOperand1(), varTok->astOperand2() };
for (int nr = 0; nr < 2; nr++) {
const Token *t = tokens[nr];
while (t && (t->str() == "." || t->str() == "::"))
t = t->astOperand2();
if (t && t->variable() && t->variable()->isPointer())
varTok = t;
}
}
if (varTok->str() == "*") {
if (!_tokenizer->isC() || varTok->astOperand2() != nullptr || litTok->tokType() != Token::eString)
continue;
varTok = varTok->astOperand1();
}
while (varTok && (varTok->str() == "." || varTok->str() == "::"))
varTok = varTok->astOperand2();
if (!varTok || !varTok->isName())
continue;
const Variable *var = varTok->variable();
while (Token::Match(varTok->astParent(), "[.*]"))
varTok = varTok->astParent();
const std::string varname = varTok->expressionString();
if (litTok->tokType() == Token::eString) {
if (_tokenizer->isC() || (var && var->isArrayOrPointer()))
suspiciousStringCompareError(tok, varname);
} else if (litTok->originalName() == "'\\0'" && var && var->isPointer()) {
suspiciousStringCompareError_char(tok, varname);
}
}
}
}
void CheckString::suspiciousStringCompareError(const Token* tok, const std::string& var)
{
reportError(tok, Severity::warning, "literalWithCharPtrCompare",
"String literal compared with variable '" + var + "'. Did you intend to use strcmp() instead?");
}
void CheckString::suspiciousStringCompareError_char(const Token* tok, const std::string& var)
{
reportError(tok, Severity::warning, "charLiteralWithCharPtrCompare",
"Char literal compared with pointer '" + var + "'. Did you intend to dereference it?");
}
//---------------------------------------------------------------------------
// Adding C-string and char with operator+
//---------------------------------------------------------------------------
static bool isChar(const Variable* var)
{
return (var && !var->isPointer() && !var->isArray() && var->typeStartToken()->str() == "char");
}
void CheckString::strPlusChar()
{
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (tok->str() == "+") {
if (tok->astOperand1() && (tok->astOperand1()->tokType() == Token::eString)) { // string literal...
if (tok->astOperand2() && (tok->astOperand2()->tokType() == Token::eChar || isChar(tok->astOperand2()->variable()))) // added to char variable or char constant
strPlusCharError(tok);
}
}
}
}
}
void CheckString::strPlusCharError(const Token *tok)
{
reportError(tok, Severity::error, "strPlusChar", "Unusual pointer arithmetic. A value of type 'char' is added to a string literal.");
}
//---------------------------------------------------------------------------
// Implicit casts of string literals to bool
// Comparing string literal with strlen() with wrong length
//---------------------------------------------------------------------------
void CheckString::checkIncorrectStringCompare()
{
if (!_settings->isEnabled("warning"))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
// skip "assert(str && ..)" and "assert(.. && str)"
if (tok->str().size() >= 6U && (tok->str().find("assert") == tok->str().size() - 6U || tok->str().find("ASSERT") == tok->str().size() - 6U) &&
Token::Match(tok, "%name% (") &&
(Token::Match(tok->tokAt(2), "%str% &&") || Token::Match(tok->next()->link()->tokAt(-2), "&& %str% )")))
tok = tok->next()->link();
if (Token::simpleMatch(tok, ". substr (") && Token::Match(tok->tokAt(3)->nextArgument(), "%num% )")) {
MathLib::bigint clen = MathLib::toLongNumber(tok->linkAt(2)->strAt(-1));
const Token* begin = tok->previous();
for (;;) { // Find start of statement
while (begin->link() && Token::Match(begin, "]|)|>"))
begin = begin->link()->previous();
if (Token::Match(begin->previous(), ".|::"))
begin = begin->tokAt(-2);
else
break;
}
begin = begin->previous();
const Token* end = tok->linkAt(2)->next();
if (Token::Match(begin->previous(), "%str% ==|!=") && begin->strAt(-2) != "+") {
std::size_t slen = Token::getStrLength(begin->previous());
if (clen != (int)slen) {
incorrectStringCompareError(tok->next(), "substr", begin->strAt(-1));
}
} else if (Token::Match(end, "==|!= %str% !!+")) {
std::size_t slen = Token::getStrLength(end->next());
if (clen != (int)slen) {
incorrectStringCompareError(tok->next(), "substr", end->strAt(1));
}
}
} else if (Token::Match(tok, "&&|%oror%|( %str% &&|%oror%|)") && !Token::Match(tok, "( %str% )")) {
incorrectStringBooleanError(tok->next(), tok->strAt(1));
} else if (Token::Match(tok, "if|while ( %str% )")) {
incorrectStringBooleanError(tok->tokAt(2), tok->strAt(2));
}
}
}
}
void CheckString::incorrectStringCompareError(const Token *tok, const std::string& func, const std::string &string)
{
reportError(tok, Severity::warning, "incorrectStringCompare", "String literal " + string + " doesn't match length argument for " + func + "().");
}
void CheckString::incorrectStringBooleanError(const Token *tok, const std::string& string)
{
reportError(tok, Severity::warning, "incorrectStringBooleanError", "Conversion of string literal " + string + " to bool always evaluates to true.");
}
//---------------------------------------------------------------------------
// Overlapping source and destination passed to sprintf().
//---------------------------------------------------------------------------
void CheckString::sprintfOverlappingData()
{
const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
// Get variable id of target buffer..
unsigned int varid = 0;
if (Token::Match(tok, "sprintf|snprintf|swprintf ( %var% ,"))
varid = tok->tokAt(2)->varId();
else if (Token::Match(tok, "sprintf|snprintf|swprintf ( %name% . %var% ,"))
varid = tok->tokAt(4)->varId();
else
continue;
// goto next argument
const Token *tok2 = tok->tokAt(2)->nextArgument();
if (tok->str() == "snprintf" || tok->str() == "swprintf") { // Jump over second parameter for snprintf and swprintf
tok2 = tok2->nextArgument();
if (!tok2)
continue;
}
// is any source buffer overlapping the target buffer?
do {
if (Token::Match(tok2, "%varid% [,)]", varid)) {
sprintfOverlappingDataError(tok2, tok2->str());
break;
}
} while (nullptr != (tok2 = tok2->nextArgument()));
}
}
}
void CheckString::sprintfOverlappingDataError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::error, "sprintfOverlappingData",
"Undefined behavior: Variable '" + varname + "' is used as parameter and destination in s[n]printf().\n"
"The variable '" + varname + "' is used both as a parameter and as destination in "
"s[n]printf(). The origin and destination buffers overlap. Quote from glibc (C-library) "
"documentation (http://www.gnu.org/software/libc/manual/html_mono/libc.html#Formatted-Output-Functions): "
"\"If copying takes place between objects that overlap as a result of a call "
"to sprintf() or snprintf(), the results are undefined.\"");
}
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