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cppcheck/lib/checksizeof.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2023 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 "checksizeof.h"
#include "errortypes.h"
#include "library.h"
#include "settings.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"
#include <algorithm>
#include <iterator>
#include <map>
#include <vector>
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckSizeof instance;
}
// CWE IDs used:
static const struct CWE CWE398(398U); // Indicator of Poor Code Quality
static const struct CWE CWE467(467U); // Use of sizeof() on a Pointer Type
static const struct CWE CWE682(682U); // Incorrect Calculation
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
void CheckSizeof::checkSizeofForNumericParameter()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::checkSizeofForNumericParameter"); // warning
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, "sizeof ( %num% )") ||
Token::Match(tok, "sizeof %num%")) {
sizeofForNumericParameterError(tok);
}
}
}
}
void CheckSizeof::sizeofForNumericParameterError(const Token *tok)
{
reportError(tok, Severity::warning,
"sizeofwithnumericparameter", "Suspicious usage of 'sizeof' with a numeric constant as parameter.\n"
"It is unusual to use a constant value with sizeof. For example, 'sizeof(10)'"
" returns 4 (in 32-bit systems) or 8 (in 64-bit systems) instead of 10. 'sizeof('A')'"
" and 'sizeof(char)' can return different results.", CWE682, Certainty::normal);
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
void CheckSizeof::checkSizeofForArrayParameter()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::checkSizeofForArrayParameter"); // warning
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, "sizeof ( %var% )") ||
Token::Match(tok, "sizeof %var% !![")) {
const Token* varTok = tok->next();
if (varTok->str() == "(") {
varTok = varTok->next();
}
const Variable *var = varTok->variable();
if (var && var->isArray() && var->isArgument() && !var->isReference())
sizeofForArrayParameterError(tok);
}
}
}
}
void CheckSizeof::sizeofForArrayParameterError(const Token *tok)
{
reportError(tok, Severity::warning,
"sizeofwithsilentarraypointer", "Using 'sizeof' on array given as function argument "
"returns size of a pointer.\n"
"Using 'sizeof' for array given as function argument returns the size of a pointer. "
"It does not return the size of the whole array in bytes as might be "
"expected. For example, this code:\n"
" int f(char a[100]) {\n"
" return sizeof(a);\n"
" }\n"
"returns 4 (in 32-bit systems) or 8 (in 64-bit systems) instead of 100 (the "
"size of the array in bytes).", CWE467, Certainty::normal
);
}
void CheckSizeof::checkSizeofForPointerSize()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::checkSizeofForPointerSize"); // warning
const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
const Token* tokSize;
const Token* tokFunc;
const Token *variable = nullptr;
const Token *variable2 = nullptr;
// Find any function that may use sizeof on a pointer
// Once leaving those tests, it is mandatory to have:
// - variable matching the used pointer
// - tokVar pointing on the argument where sizeof may be used
if (Token::Match(tok->tokAt(2), "%name% (") && mSettings->library.getAllocFuncInfo(tok->tokAt(2))) {
if (Token::Match(tok, "%var% ="))
variable = tok;
else if (tok->strAt(1) == ")" && Token::Match(tok->linkAt(1)->tokAt(-2), "%var% ="))
variable = tok->linkAt(1)->tokAt(-2);
else if (tok->link() && Token::Match(tok, "> ( %name% (") && mSettings->library.getAllocFuncInfo(tok->tokAt(2)) && Token::Match(tok->link()->tokAt(-3), "%var% ="))
variable = tok->link()->tokAt(-3);
tokSize = tok->tokAt(4);
tokFunc = tok->tokAt(2);
} else if (Token::simpleMatch(tok, "memset (") && tok->strAt(-1) != ".") {
variable = tok->tokAt(2);
tokSize = variable->nextArgument();
if (tokSize)
tokSize = tokSize->nextArgument();
tokFunc = tok;
} else if (Token::Match(tok, "memcpy|memcmp|memmove|strncpy|strncmp|strncat (") && tok->strAt(-1) != ".") {
variable = tok->tokAt(2);
variable2 = variable->nextArgument();
if (!variable2)
continue;
tokSize = variable2->nextArgument();
tokFunc = tok;
} else {
continue;
}
if (tokSize && tokFunc->str() == "calloc")
tokSize = tokSize->nextArgument();
if (tokSize) {
const Token * const paramsListEndTok = tokFunc->linkAt(1);
for (const Token* tok2 = tokSize; tok2 != paramsListEndTok; tok2 = tok2->next()) {
if (Token::simpleMatch(tok2, "/ sizeof")) {
// Allow division with sizeof(char)
if (Token::simpleMatch(tok2->next(), "sizeof (")) {
const Token *sztok = tok2->tokAt(2)->astOperand2();
const ValueType *vt = ((sztok != nullptr) ? sztok->valueType() : nullptr);
if (vt && vt->type == ValueType::CHAR && vt->pointer == 0)
continue;
}
auto hasMultiplication = [](const Token* parTok) -> bool {
while (parTok) { // Allow division if followed by multiplication
if (parTok->isArithmeticalOp() && parTok->str() == "*") {
const Token* szToks[] = { parTok->astOperand1(), parTok->astOperand2() };
if (std::any_of(std::begin(szToks), std::end(szToks), [](const Token* szTok) {
return Token::simpleMatch(szTok, "(") && Token::simpleMatch(szTok->previous(), "sizeof");
}))
return true;
}
parTok = parTok->astParent();
}
return false;
};
if (hasMultiplication(tok2->astParent()))
continue;
divideBySizeofError(tok2, tokFunc->str());
}
}
}
if (!variable || !tokSize)
continue;
while (Token::Match(variable, "%var% ::|."))
variable = variable->tokAt(2);
while (Token::Match(variable2, "%var% ::|."))
variable2 = variable2->tokAt(2);
if (!variable)
continue;
// Ensure the variables are in the symbol database
// Also ensure the variables are pointers
// Only keep variables which are pointers
const Variable *var = variable->variable();
if (!var || !var->isPointer() || var->isArray()) {
variable = nullptr;
}
if (variable2) {
var = variable2->variable();
if (!var || !var->isPointer() || var->isArray()) {
variable2 = nullptr;
}
}
// If there are no pointer variable at this point, there is
// no need to continue
if (variable == nullptr && variable2 == nullptr) {
continue;
}
// Jump to the next sizeof token in the function and in the parameter
// This is to allow generic operations with sizeof
for (; tokSize && tokSize->str() != ")" && tokSize->str() != "," && tokSize->str() != "sizeof"; tokSize = tokSize->next()) {}
if (tokSize->str() != "sizeof")
continue;
// Now check for the sizeof usage: Does the level of pointer indirection match?
if (tokSize->linkAt(1)->strAt(-1) == "*") {
if (variable && variable->valueType() && variable->valueType()->pointer == 1 && variable->valueType()->type != ValueType::VOID)
sizeofForPointerError(variable, variable->str());
else if (variable2 && variable2->valueType() && variable2->valueType()->pointer == 1 && variable2->valueType()->type != ValueType::VOID)
sizeofForPointerError(variable2, variable2->str());
}
if (Token::simpleMatch(tokSize, "sizeof ( &"))
tokSize = tokSize->tokAt(3);
else if (Token::Match(tokSize, "sizeof (|&"))
tokSize = tokSize->tokAt(2);
else
tokSize = tokSize->next();
while (Token::Match(tokSize, "%var% ::|."))
tokSize = tokSize->tokAt(2);
if (Token::Match(tokSize, "%var% [|("))
continue;
// Now check for the sizeof usage again. Once here, everything using sizeof(varid) or sizeof(&varid)
// looks suspicious
if (variable && tokSize->varId() == variable->varId())
sizeofForPointerError(variable, variable->str());
if (variable2 && tokSize->varId() == variable2->varId())
sizeofForPointerError(variable2, variable2->str());
}
}
}
void CheckSizeof::sizeofForPointerError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::warning, "pointerSize",
"Size of pointer '" + varname + "' used instead of size of its data.\n"
"Size of pointer '" + varname + "' used instead of size of its data. "
"This is likely to lead to a buffer overflow. You probably intend to "
"write 'sizeof(*" + varname + ")'.", CWE467, Certainty::normal);
}
void CheckSizeof::divideBySizeofError(const Token *tok, const std::string &memfunc)
{
reportError(tok, Severity::warning, "sizeofDivisionMemfunc",
"Division by result of sizeof(). " + memfunc + "() expects a size in bytes, did you intend to multiply instead?", CWE682, Certainty::normal);
}
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckSizeof::sizeofsizeof()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::sizeofsizeof"); // warning
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (Token::Match(tok, "sizeof (| sizeof")) {
sizeofsizeofError(tok);
tok = tok->next();
}
}
}
void CheckSizeof::sizeofsizeofError(const Token *tok)
{
reportError(tok, Severity::warning,
"sizeofsizeof", "Calling 'sizeof' on 'sizeof'.\n"
"Calling sizeof for 'sizeof looks like a suspicious code and "
"most likely there should be just one 'sizeof'. The current "
"code is equivalent to 'sizeof(size_t)'", CWE682, Certainty::normal);
}
//-----------------------------------------------------------------------------
void CheckSizeof::sizeofCalculation()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::sizeofCalculation"); // warning
const bool printInconclusive = mSettings->certainty.isEnabled(Certainty::inconclusive);
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (!Token::simpleMatch(tok, "sizeof ("))
continue;
// ignore if the `sizeof` result is cast to void inside a macro, i.e. the calculation is
// expected to be parsed but skipped, such as in a disabled custom ASSERT() macro
if (tok->isExpandedMacro() && tok->previous()) {
const Token *cast_end = (tok->previous()->str() == "(") ? tok->previous() : tok;
if (Token::simpleMatch(cast_end->tokAt(-3), "( void )") ||
Token::simpleMatch(cast_end->tokAt(-4), "static_cast < void >")) {
continue;
}
}
const Token *argument = tok->next()->astOperand2();
if (!argument || !argument->isCalculation())
continue;
bool inconclusive = false;
if (argument->isExpandedMacro())
inconclusive = true;
else if (tok->next()->isExpandedMacro())
inconclusive = true;
if (!inconclusive || printInconclusive)
sizeofCalculationError(argument, inconclusive);
}
}
void CheckSizeof::sizeofCalculationError(const Token *tok, bool inconclusive)
{
reportError(tok, Severity::warning,
"sizeofCalculation", "Found calculation inside sizeof().", CWE682, inconclusive ? Certainty::inconclusive : Certainty::normal);
}
//-----------------------------------------------------------------------------
void CheckSizeof::sizeofFunction()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
logChecker("CheckSizeof::sizeofFunction"); // warning
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (Token::simpleMatch(tok, "sizeof (")) {
// ignore if the `sizeof` result is cast to void inside a macro, i.e. the calculation is
// expected to be parsed but skipped, such as in a disabled custom ASSERT() macro
if (tok->isExpandedMacro() && tok->previous()) {
const Token *cast_end = (tok->previous()->str() == "(") ? tok->previous() : tok;
if (Token::simpleMatch(cast_end->tokAt(-3), "( void )") ||
Token::simpleMatch(cast_end->tokAt(-4), "static_cast < void >")) {
continue;
}
}
if (const Token *argument = tok->next()->astOperand2()) {
const Token *checkToken = argument->previous();
if (checkToken->tokType() == Token::eName)
break;
const Function * fun = checkToken->function();
// Don't report error if the function is overloaded
if (fun && fun->nestedIn->functionMap.count(checkToken->str()) == 1) {
sizeofFunctionError(tok);
}
}
}
}
}
void CheckSizeof::sizeofFunctionError(const Token *tok)
{
reportError(tok, Severity::warning,
"sizeofFunctionCall", "Found function call inside sizeof().", CWE682, Certainty::normal);
}
//-----------------------------------------------------------------------------
// Check for code like sizeof()*sizeof() or sizeof(ptr)/value
//-----------------------------------------------------------------------------
void CheckSizeof::suspiciousSizeofCalculation()
{
if (!mSettings->severity.isEnabled(Severity::warning) || !mSettings->certainty.isEnabled(Certainty::inconclusive))
return;
logChecker("CheckSizeof::suspiciousSizeofCalculation"); // warning,inconclusive
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (Token::simpleMatch(tok, "sizeof (")) {
const Token* lPar = tok->astParent();
if (lPar && lPar->str() == "(") {
const Token* const rPar = lPar->link();
const Token* varTok = lPar->astOperand2();
int derefCount = 0;
while (Token::Match(varTok, "[|*")) {
++derefCount;
varTok = varTok->astOperand1();
}
if (lPar->astParent() && lPar->astParent()->str() == "/") {
const Variable* var = varTok ? varTok->variable() : nullptr;
if (var && var->isPointer() && !var->isArray() && !(var->valueType() && var->valueType()->pointer <= derefCount))
divideSizeofError(tok);
}
else if (Token::simpleMatch(rPar, ") * sizeof") && rPar->next()->astOperand1() == tok->next())
multiplySizeofError(tok);
}
}
}
}
void CheckSizeof::multiplySizeofError(const Token *tok)
{
reportError(tok, Severity::warning,
"multiplySizeof", "Multiplying sizeof() with sizeof() indicates a logic error.", CWE682, Certainty::inconclusive);
}
void CheckSizeof::divideSizeofError(const Token *tok)
{
reportError(tok, Severity::warning,
"divideSizeof", "Division of result of sizeof() on pointer type.\n"
"Division of result of sizeof() on pointer type. sizeof() returns the size of the pointer, "
"not the size of the memory area it points to.", CWE682, Certainty::inconclusive);
}
void CheckSizeof::sizeofVoid()
{
if (!mSettings->severity.isEnabled(Severity::portability))
return;
logChecker("CheckSizeof::sizeofVoid"); // portability
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (Token::simpleMatch(tok, "sizeof ( void )")) {
sizeofVoidError(tok);
} else if (Token::simpleMatch(tok, "sizeof (") && tok->next()->astOperand2()) {
const ValueType *vt = tok->next()->astOperand2()->valueType();
if (vt && vt->type == ValueType::Type::VOID && vt->pointer == 0U)
sizeofDereferencedVoidPointerError(tok, tok->strAt(3));
} else if (tok->str() == "-") {
// only warn for: 'void *' - 'integral'
const ValueType *vt1 = tok->astOperand1() ? tok->astOperand1()->valueType() : nullptr;
const ValueType *vt2 = tok->astOperand2() ? tok->astOperand2()->valueType() : nullptr;
const bool op1IsvoidPointer = (vt1 && vt1->type == ValueType::Type::VOID && vt1->pointer == 1U);
const bool op2IsIntegral = (vt2 && vt2->isIntegral() && vt2->pointer == 0U);
if (op1IsvoidPointer && op2IsIntegral)
arithOperationsOnVoidPointerError(tok, tok->astOperand1()->expressionString(), vt1->str());
} else if (Token::Match(tok, "+|++|--|+=|-=")) { // Arithmetic operations on variable of type "void*"
const ValueType *vt1 = tok->astOperand1() ? tok->astOperand1()->valueType() : nullptr;
const ValueType *vt2 = tok->astOperand2() ? tok->astOperand2()->valueType() : nullptr;
const bool voidpointer1 = (vt1 && vt1->type == ValueType::Type::VOID && vt1->pointer == 1U);
const bool voidpointer2 = (vt2 && vt2->type == ValueType::Type::VOID && vt2->pointer == 1U);
if (voidpointer1)
arithOperationsOnVoidPointerError(tok, tok->astOperand1()->expressionString(), vt1->str());
if (!tok->isAssignmentOp() && voidpointer2)
arithOperationsOnVoidPointerError(tok, tok->astOperand2()->expressionString(), vt2->str());
}
}
}
void CheckSizeof::sizeofVoidError(const Token *tok)
{
const std::string message = "Behaviour of 'sizeof(void)' is not covered by the ISO C standard.";
const std::string verbose = message + " A value for 'sizeof(void)' is defined only as part of a GNU C extension, which defines 'sizeof(void)' to be 1.";
reportError(tok, Severity::portability, "sizeofVoid", message + "\n" + verbose, CWE682, Certainty::normal);
}
void CheckSizeof::sizeofDereferencedVoidPointerError(const Token *tok, const std::string &varname)
{
const std::string message = "'*" + varname + "' is of type 'void', the behaviour of 'sizeof(void)' is not covered by the ISO C standard.";
const std::string verbose = message + " A value for 'sizeof(void)' is defined only as part of a GNU C extension, which defines 'sizeof(void)' to be 1.";
reportError(tok, Severity::portability, "sizeofDereferencedVoidPointer", message + "\n" + verbose, CWE682, Certainty::normal);
}
void CheckSizeof::arithOperationsOnVoidPointerError(const Token* tok, const std::string &varname, const std::string &vartype)
{
const std::string message = "'$symbol' is of type '" + vartype + "'. When using void pointers in calculations, the behaviour is undefined.";
const std::string verbose = message + " Arithmetic operations on 'void *' is a GNU C extension, which defines the 'sizeof(void)' to be 1.";
reportError(tok, Severity::portability, "arithOperationsOnVoidPointer", "$symbol:" + varname + '\n' + message + '\n' + verbose, CWE467, Certainty::normal);
}
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