/*
 * Cppcheck - A tool for static C/C++ code analysis
 * Copyright (C) 2007-2020 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 "settings.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"

#include <cstddef>
//---------------------------------------------------------------------------

// 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->isEnabled(Settings::WARNING))
 return;

 const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
 for (const Scope * scope : symbolDatabase->functionScopes) {
 for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
 if (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, false);
}


//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
void CheckSizeof::checkSizeofForArrayParameter()
{
 if (!mSettings->isEnabled(Settings::WARNING))
 return;
 const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
 for (const Scope * scope : symbolDatabase->functionScopes) {
 for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
 if (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, false
 );
}

void CheckSizeof::checkSizeofForPointerSize()
{
 if (!mSettings->isEnabled(Settings::WARNING))
 return;

 const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
 for (const Scope * scope : symbolDatabase->functionScopes) {
 for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
 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), "malloc|alloca|calloc (")) {
 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, "> ( malloc|alloca|calloc (") && 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;
 }

 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);

 // 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, false);
}

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, false);
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckSizeof::sizeofsizeof()
{
 if (!mSettings->isEnabled(Settings::WARNING))
 return;

 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, false);
}

//-----------------------------------------------------------------------------

void CheckSizeof::sizeofCalculation()
{
 if (!mSettings->isEnabled(Settings::WARNING))
 return;

 const bool printInconclusive = mSettings->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->previous(), "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);
}

//-----------------------------------------------------------------------------

void CheckSizeof::sizeofFunction()
{
 if (!mSettings->isEnabled(Settings::WARNING))
 return;

 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->previous(), "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, false);
}

//-----------------------------------------------------------------------------
// Check for code like sizeof()*sizeof() or sizeof(ptr)/value
//-----------------------------------------------------------------------------
void CheckSizeof::suspiciousSizeofCalculation()
{
 if (!mSettings->isEnabled(Settings::WARNING) || !mSettings->inconclusive)
 return;

 // TODO: Use AST here. This should be possible as soon as sizeof without brackets is correctly parsed
 for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
 if (Token::simpleMatch(tok, "sizeof (")) {
 const Token* const end = tok->linkAt(1);
 const Variable* var = end->previous()->variable();
 if (end->strAt(-1) == "*" || (var && var->isPointer() && !var->isArray())) {
 if (end->strAt(1) == "/")
 divideSizeofError(tok);
 } else if (Token::simpleMatch(end, ") * sizeof") && end->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, true);
}

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, true);
}

void CheckSizeof::sizeofVoid()
{
 if (!mSettings->isEnabled(Settings::PORTABILITY))
 return;

 for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
 if (Token::simpleMatch(tok, "sizeof ( )")) { // "sizeof(void)" gets simplified to sizeof ( )
 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, false);
}

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, false);
}

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, false);
}