/*
 * 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/>.
 */

//---------------------------------------------------------------------------
// Check functions
//---------------------------------------------------------------------------

#include "checkfunctions.h"

#include "astutils.h"
#include "mathlib.h"
#include "standards.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"
#include "valueflow.h"

#include <cmath>
#include <cstddef>
#include <iomanip>
#include <ostream>
#include <vector>

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


// Register this check class (by creating a static instance of it)
namespace {
 CheckFunctions instance;
}

static const CWE CWE252(252U); // Unchecked Return Value
static const CWE CWE477(477U); // Use of Obsolete Functions
static const CWE CWE758(758U); // Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
static const CWE CWE628(628U); // Function Call with Incorrectly Specified Arguments
static const CWE CWE686(686U); // Function Call With Incorrect Argument Type
static const CWE CWE687(687U); // Function Call With Incorrectly Specified Argument Value
static const CWE CWE688(688U); // Function Call With Incorrect Variable or Reference as Argument

void CheckFunctions::checkProhibitedFunctions()
{
 const bool checkAlloca = mSettings->isEnabled(Settings::WARNING) && ((mSettings->standards.c >= Standards::C99 && mTokenizer->isC()) || mSettings->standards.cpp >= Standards::CPP11);

 const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
 for (const Scope *scope : symbolDatabase->functionScopes) {
 for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
 if (!Token::Match(tok, "%name% (") && tok->varId() == 0)
 continue;
 // alloca() is special as it depends on the code being C or C++, so it is not in Library
 if (checkAlloca && Token::simpleMatch(tok, "alloca (") && (!tok->function() || tok->function()->nestedIn->type == Scope::eGlobal)) {
 if (mTokenizer->isC()) {
 if (mSettings->standards.c > Standards::C89)
 reportError(tok, Severity::warning, "allocaCalled",
 "$symbol:alloca\n"
 "Obsolete function 'alloca' called. In C99 and later it is recommended to use a variable length array instead.\n"
 "The obsolete function 'alloca' is called. In C99 and later it is recommended to use a variable length array or "
 "a dynamically allocated array instead. The function 'alloca' is dangerous for many reasons "
 "(http://stackoverflow.com/questions/1018853/why-is-alloca-not-considered-good-practice and http://linux.die.net/man/3/alloca).");
 } else
 reportError(tok, Severity::warning, "allocaCalled",
 "$symbol:alloca\n"
 "Obsolete function 'alloca' called.\n"
 "The obsolete function 'alloca' is called. In C++11 and later it is recommended to use std::array<> or "
 "a dynamically allocated array instead. The function 'alloca' is dangerous for many reasons "
 "(http://stackoverflow.com/questions/1018853/why-is-alloca-not-considered-good-practice and http://linux.die.net/man/3/alloca).");
 } else {
 if (tok->function() && tok->function()->hasBody())
 continue;

 const Library::WarnInfo* wi = mSettings->library.getWarnInfo(tok);
 if (wi) {
 if (mSettings->isEnabled(wi->severity) && mSettings->standards.c >= wi->standards.c && mSettings->standards.cpp >= wi->standards.cpp) {
 reportError(tok, wi->severity, tok->str() + "Called", wi->message, CWE477, false);
 }
 }
 }
 }
 }
}

//---------------------------------------------------------------------------
// Check <valid> and <not-bool>
//---------------------------------------------------------------------------
void CheckFunctions::invalidFunctionUsage()
{
 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, "%name% ( !!)"))
 continue;
 const Token * const functionToken = tok;
 const std::vector<const Token *> arguments = getArguments(tok);
 for (int argnr = 1; argnr <= arguments.size(); ++argnr) {
 const Token * const argtok = arguments[argnr-1];

 // check <valid>...</valid>
 const ValueFlow::Value *invalidValue = argtok->getInvalidValue(functionToken,argnr,mSettings);
 if (invalidValue) {
 invalidFunctionArgError(argtok, functionToken->next()->astOperand1()->expressionString(), argnr, invalidValue, mSettings->library.validarg(functionToken, argnr));
 }

 if (astIsBool(argtok)) {
 // check <not-bool>
 if (mSettings->library.isboolargbad(functionToken, argnr))
 invalidFunctionArgBoolError(argtok, functionToken->str(), argnr);

 // Are the values 0 and 1 valid?
 else if (!mSettings->library.isIntArgValid(functionToken, argnr, 0))
 invalidFunctionArgError(argtok, functionToken->str(), argnr, nullptr, mSettings->library.validarg(functionToken, argnr));
 else if (!mSettings->library.isIntArgValid(functionToken, argnr, 1))
 invalidFunctionArgError(argtok, functionToken->str(), argnr, nullptr, mSettings->library.validarg(functionToken, argnr));
 }

 if (mSettings->library.isargstrz(functionToken, argnr)) {
 if (Token::Match(argtok, "& %var% !![") && argtok->next() && argtok->next()->valueType()) {
 const ValueType * valueType = argtok->next()->valueType();
 const Variable * variable = argtok->next()->variable();
 if (valueType->type == ValueType::Type::CHAR && !variable->isArray() && !variable->isGlobal() &&
 (!argtok->next()->hasKnownValue() || argtok->next()->getValue(0) == nullptr)) {
 invalidFunctionArgStrError(argtok, functionToken->str(), argnr);
 }
 }
 }
 }
 }
 }
}

void CheckFunctions::invalidFunctionArgError(const Token *tok, const std::string &functionName, int argnr, const ValueFlow::Value *invalidValue, const std::string &validstr)
{
 std::ostringstream errmsg;
 errmsg << "$symbol:" << functionName << '\n';
 if (invalidValue && invalidValue->condition)
 errmsg << ValueFlow::eitherTheConditionIsRedundant(invalidValue->condition)
 << " or $symbol() argument nr " << argnr << " can have invalid value.";
 else
 errmsg << "Invalid $symbol() argument nr " << argnr << '.';
 if (invalidValue)
 errmsg << " The value is " << std::setprecision(10) << (invalidValue->isIntValue() ? invalidValue->intvalue : invalidValue->floatValue) << " but the valid values are '" << validstr << "'.";
 else
 errmsg << " The value is 0 or 1 (boolean) but the valid values are '" << validstr << "'.";
 if (invalidValue)
 reportError(getErrorPath(tok, invalidValue, "Invalid argument"),
 invalidValue->errorSeverity() ? Severity::error : Severity::warning,
 "invalidFunctionArg",
 errmsg.str(),
 CWE628,
 invalidValue->isInconclusive());
 else
 reportError(tok,
 Severity::error,
 "invalidFunctionArg",
 errmsg.str(),
 CWE628,
 false);
}

void CheckFunctions::invalidFunctionArgBoolError(const Token *tok, const std::string &functionName, int argnr)
{
 std::ostringstream errmsg;
 errmsg << "$symbol:" << functionName << '\n';
 errmsg << "Invalid $symbol() argument nr " << argnr << ". A non-boolean value is required.";
 reportError(tok, Severity::error, "invalidFunctionArgBool", errmsg.str(), CWE628, false);
}

void CheckFunctions::invalidFunctionArgStrError(const Token *tok, const std::string &functionName, nonneg int argnr)
{
 std::ostringstream errmsg;
 errmsg << "$symbol:" << functionName << '\n';
 errmsg << "Invalid $symbol() argument nr " << argnr << ". A nul-terminated string is required.";
 reportError(tok, Severity::error, "invalidFunctionArgStr", errmsg.str(), CWE628, false);
}

//---------------------------------------------------------------------------
// Check for ignored return values.
//---------------------------------------------------------------------------
void CheckFunctions::checkIgnoredReturnValue()
{
 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()) {
 // skip c++11 initialization, ({...})
 if (Token::Match(tok, "%var%|(|,|return {"))
 tok = tok->linkAt(1);
 else if (Token::Match(tok, "[(<]") && tok->link())
 tok = tok->link();

 if (tok->varId() || !Token::Match(tok, "%name% ("))
 continue;

 if (tok->next()->astParent())
 continue;

 if (!tok->scope()->isExecutable()) {
 tok = tok->scope()->bodyEnd;
 continue;
 }

 if ((!tok->function() || !Token::Match(tok->function()->retDef, "void %name%")) &&
 (mSettings->library.isUseRetVal(tok) || (tok->function() && tok->function()->isAttributeNodiscard())) &&
 !WRONG_DATA(!tok->next()->astOperand1(), tok)) {
 ignoredReturnValueError(tok, tok->next()->astOperand1()->expressionString());
 }
 }
 }
}

void CheckFunctions::ignoredReturnValueError(const Token* tok, const std::string& function)
{
 reportError(tok, Severity::warning, "ignoredReturnValue",
 "$symbol:" + function + "\nReturn value of function $symbol() is not used.", CWE252, false);
}


//---------------------------------------------------------------------------
// Detect passing wrong values to <cmath> functions like atan(0, x);
//---------------------------------------------------------------------------
void CheckFunctions::checkMathFunctions()
{
 const bool styleC99 = mSettings->isEnabled(Settings::STYLE) && mSettings->standards.c != Standards::C89 && mSettings->standards.cpp != Standards::CPP03;
 const bool printWarnings = mSettings->isEnabled(Settings::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 (tok->varId())
 continue;
 if (printWarnings && Token::Match(tok, "%name% ( !!)")) {
 if (tok->strAt(-1) != "."
 && Token::Match(tok, "log|logf|logl|log10|log10f|log10l|log2|log2f|log2l ( %num% )")) {
 const std::string& number = tok->strAt(2);
 if ((MathLib::isInt(number) && MathLib::toLongNumber(number) <= 0) ||
 (MathLib::isFloat(number) && MathLib::toDoubleNumber(number) <= 0.))
 mathfunctionCallWarning(tok);
 } else if (Token::Match(tok, "log1p|log1pf|log1pl ( %num% )")) {
 const std::string& number = tok->strAt(2);
 if ((MathLib::isInt(number) && MathLib::toLongNumber(number) <= -1) ||
 (MathLib::isFloat(number) && MathLib::toDoubleNumber(number) <= -1.))
 mathfunctionCallWarning(tok);
 }
 // atan2 ( x , y): x and y can not be zero, because this is mathematically not defined
 else if (Token::Match(tok, "atan2|atan2f|atan2l ( %num% , %num% )")) {
 if (MathLib::isNullValue(tok->strAt(2)) && MathLib::isNullValue(tok->strAt(4)))
 mathfunctionCallWarning(tok, 2);
 }
 // fmod ( x , y) If y is zero, then either a range error will occur or the function will return zero (implementation-defined).
 else if (Token::Match(tok, "fmod|fmodf|fmodl (")) {
 const Token* nextArg = tok->tokAt(2)->nextArgument();
 if (nextArg && MathLib::isNullValue(nextArg->str()))
 mathfunctionCallWarning(tok, 2);
 }
 // pow ( x , y) If x is zero, and y is negative --> division by zero
 else if (Token::Match(tok, "pow|powf|powl ( %num% , %num% )")) {
 if (MathLib::isNullValue(tok->strAt(2)) && MathLib::isNegative(tok->strAt(4)))
 mathfunctionCallWarning(tok, 2);
 }
 }

 if (styleC99) {
 if (Token::Match(tok, "%num% - erf (") && Tokenizer::isOneNumber(tok->str()) && tok->next()->astOperand2() == tok->tokAt(3)) {
 mathfunctionCallWarning(tok, "1 - erf(x)", "erfc(x)");
 } else if (Token::simpleMatch(tok, "exp (") && Token::Match(tok->linkAt(1), ") - %num%") && Tokenizer::isOneNumber(tok->linkAt(1)->strAt(2)) && tok->linkAt(1)->next()->astOperand1() == tok->next()) {
 mathfunctionCallWarning(tok, "exp(x) - 1", "expm1(x)");
 } else if (Token::simpleMatch(tok, "log (") && tok->next()->astOperand2()) {
 const Token* plus = tok->next()->astOperand2();
 if (plus->str() == "+" && ((plus->astOperand1() && Tokenizer::isOneNumber(plus->astOperand1()->str())) || (plus->astOperand2() && Tokenizer::isOneNumber(plus->astOperand2()->str()))))
 mathfunctionCallWarning(tok, "log(1 + x)", "log1p(x)");
 }
 }
 }
 }
}

void CheckFunctions::mathfunctionCallWarning(const Token *tok, const nonneg int numParam)
{
 if (tok) {
 if (numParam == 1)
 reportError(tok, Severity::warning, "wrongmathcall", "$symbol:" + tok->str() + "\nPassing value " + tok->strAt(2) + " to $symbol() leads to implementation-defined result.", CWE758, false);
 else if (numParam == 2)
 reportError(tok, Severity::warning, "wrongmathcall", "$symbol:" + tok->str() + "\nPassing values " + tok->strAt(2) + " and " + tok->strAt(4) + " to $symbol() leads to implementation-defined result.", CWE758, false);
 } else
 reportError(tok, Severity::warning, "wrongmathcall", "Passing value '#' to #() leads to implementation-defined result.", CWE758, false);
}

void CheckFunctions::mathfunctionCallWarning(const Token *tok, const std::string& oldexp, const std::string& newexp)
{
 reportError(tok, Severity::style, "unpreciseMathCall", "Expression '" + oldexp + "' can be replaced by '" + newexp + "' to avoid loss of precision.", CWE758, false);
}

//---------------------------------------------------------------------------
// memset(p, y, 0 /* bytes to fill */) <- 2nd and 3rd arguments inverted
//---------------------------------------------------------------------------
void CheckFunctions::memsetZeroBytes()
{
// FIXME:
// Replace this with library configuration.
// For instance:
// <arg nr="3">
// <warn knownIntValue="0" severity="warning" msg="..."/>
// </arg>

 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, "memset|wmemset (") && (numberOfArguments(tok)==3)) {
 const std::vector<const Token *> &arguments = getArguments(tok);
 if (WRONG_DATA(arguments.size() != 3U, tok))
 continue;
 const Token* lastParamTok = arguments[2];
 if (MathLib::isNullValue(lastParamTok->str()))
 memsetZeroBytesError(tok);
 }
 }
 }
}

void CheckFunctions::memsetZeroBytesError(const Token *tok)
{
 const std::string summary("memset() called to fill 0 bytes.");
 const std::string verbose(summary + " The second and third arguments might be inverted."
 " The function memset ( void * ptr, int value, size_t num ) sets the"
 " first num bytes of the block of memory pointed by ptr to the specified value.");
 reportError(tok, Severity::warning, "memsetZeroBytes", summary + "\n" + verbose, CWE687, false);
}

void CheckFunctions::memsetInvalid2ndParam()
{
// FIXME:
// Replace this with library configuration.
// For instance:
// <arg nr="2">
// <not-float/>
// <warn possibleIntValue=":-129,256:" severity="warning" msg="..."/>
// </arg>

 const bool printPortability = mSettings->isEnabled(Settings::PORTABILITY);
 const bool printWarning = mSettings->isEnabled(Settings::WARNING);
 if (!printWarning && !printPortability)
 return;

 const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
 for (const Scope *scope : symbolDatabase->functionScopes) {
 for (const Token* tok = scope->bodyStart->next(); tok && (tok != scope->bodyEnd); tok = tok->next()) {
 if (!Token::simpleMatch(tok, "memset ("))
 continue;

 const std::vector<const Token *> args = getArguments(tok);
 if (args.size() != 3)
 continue;

 // Second parameter is zero literal, i.e. 0.0f
 const Token * const secondParamTok = args[1];
 if (Token::Match(secondParamTok, "%num% ,") && MathLib::isNullValue(secondParamTok->str()))
 continue;

 // Check if second parameter is a float variable or a float literal != 0.0f
 if (printPortability && astIsFloat(secondParamTok,false)) {
 memsetFloatError(secondParamTok, secondParamTok->expressionString());
 }

 if (printWarning && secondParamTok->isNumber()) { // Check if the second parameter is a literal and is out of range
 const long long int value = MathLib::toLongNumber(secondParamTok->str());
 const long long sCharMin = mSettings->signedCharMin();
 const long long uCharMax = mSettings->unsignedCharMax();
 if (value < sCharMin || value > uCharMax)
 memsetValueOutOfRangeError(secondParamTok, secondParamTok->str());
 }
 }
 }
}

void CheckFunctions::memsetFloatError(const Token *tok, const std::string &var_value)
{
 const std::string message("The 2nd memset() argument '" + var_value +
 "' is a float, its representation is implementation defined.");
 const std::string verbose(message + " memset() is used to set each byte of a block of memory to a specific value and"
 " the actual representation of a floating-point value is implementation defined.");
 reportError(tok, Severity::portability, "memsetFloat", message + "\n" + verbose, CWE688, false);
}

void CheckFunctions::memsetValueOutOfRangeError(const Token *tok, const std::string &value)
{
 const std::string message("The 2nd memset() argument '" + value + "' doesn't fit into an 'unsigned char'.");
 const std::string verbose(message + " The 2nd parameter is passed as an 'int', but the function fills the block of memory using the 'unsigned char' conversion of this value.");
 reportError(tok, Severity::warning, "memsetValueOutOfRange", message + "\n" + verbose, CWE686, false);
}

//---------------------------------------------------------------------------
// --check-library => warn for unconfigured functions
//---------------------------------------------------------------------------

void CheckFunctions::checkLibraryMatchFunctions()
{
 if (!mSettings->checkLibrary || !mSettings->isEnabled(Settings::INFORMATION))
 return;

 bool insideNew = false;
 for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
 if (!tok->scope() || !tok->scope()->isExecutable())
 continue;

 if (tok->str() == "new")
 insideNew = true;
 else if (tok->str() == ";")
 insideNew = false;
 else if (insideNew)
 continue;

 if (!Token::Match(tok, "%name% (") || Token::Match(tok, "asm|sizeof|catch"))
 continue;

 if (tok->varId() != 0 || tok->type() || tok->isStandardType() || tok->isControlFlowKeyword())
 continue;

 if (tok->linkAt(1)->strAt(1) == "(")
 continue;

 if (!mSettings->library.isNotLibraryFunction(tok))
 continue;

 const std::string &functionName = mSettings->library.getFunctionName(tok);
 if (functionName.empty() || mSettings->library.functions.find(functionName) != mSettings->library.functions.end())
 continue;

 reportError(tok,
 Severity::information,
 "checkLibraryFunction",
 "--check-library: There is no matching configuration for function " + functionName + "()");
 }
}