path: root/libsolidity/inlineasm/AsmParser.cpp

/*
    This file is part of solidity.

    solidity 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.

    solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2016
 * Solidity inline assembly parser.
 */

#include <libsolidity/inlineasm/AsmParser.h>
#include <liblangutil/Scanner.h>
#include <liblangutil/ErrorReporter.h>

#include <boost/algorithm/string.hpp>

#include <cctype>
#include <algorithm>

using namespace std;
using namespace dev;
using namespace langutil;
using namespace dev::solidity;
using namespace dev::solidity::assembly;

shared_ptr<assembly::Block> Parser::parse(std::shared_ptr<Scanner> const& _scanner, bool _reuseScanner)
{
    m_recursionDepth = 0;
    try
    {
        m_scanner = _scanner;
        auto block = make_shared<Block>(parseBlock());
        if (!_reuseScanner)
            expectToken(Token::EOS);
        return block;
    }
    catch (FatalError const&)
    {
        if (m_errorReporter.errors().empty())
            throw; // Something is weird here, rather throw again.
    }
    return nullptr;
}

assembly::Block Parser::parseBlock()
{
    RecursionGuard recursionGuard(*this);
    assembly::Block block = createWithLocation<Block>();
    expectToken(Token::LBrace);
    while (currentToken() != Token::RBrace)
        block.statements.emplace_back(parseStatement());
    block.location.end = endPosition();
    advance();
    return block;
}

assembly::Statement Parser::parseStatement()
{
    RecursionGuard recursionGuard(*this);
    switch (currentToken())
    {
    case Token::Let:
        return parseVariableDeclaration();
    case Token::Function:
        return parseFunctionDefinition();
    case Token::LBrace:
        return parseBlock();
    case Token::If:
    {
        assembly::If _if = createWithLocation<assembly::If>();
        m_scanner->next();
        _if.condition = make_shared<Expression>(parseExpression());
        _if.body = parseBlock();
        return _if;
    }
    case Token::Switch:
    {
        assembly::Switch _switch = createWithLocation<assembly::Switch>();
        m_scanner->next();
        _switch.expression = make_shared<Expression>(parseExpression());
        while (m_scanner->currentToken() == Token::Case)
            _switch.cases.emplace_back(parseCase());
        if (m_scanner->currentToken() == Token::Default)
            _switch.cases.emplace_back(parseCase());
        if (m_scanner->currentToken() == Token::Default)
            fatalParserError("Only one default case allowed.");
        else if (m_scanner->currentToken() == Token::Case)
            fatalParserError("Case not allowed after default case.");
        if (_switch.cases.empty())
            fatalParserError("Switch statement without any cases.");
        _switch.location.end = _switch.cases.back().body.location.end;
        return _switch;
    }
    case Token::For:
        return parseForLoop();
    case Token::Assign:
    {
        if (m_flavour != AsmFlavour::Loose)
            break;
        assembly::StackAssignment assignment = createWithLocation<assembly::StackAssignment>();
        advance();
        expectToken(Token::Colon);
        assignment.variableName.location = location();
        assignment.variableName.name = YulString(currentLiteral());
        if (instructions().count(assignment.variableName.name.str()))
            fatalParserError("Identifier expected, got instruction name.");
        assignment.location.end = endPosition();
        expectToken(Token::Identifier);
        return assignment;
    }
    default:
        break;
    }
    // Options left:
    // Simple instruction (might turn into functional),
    // literal,
    // identifier (might turn into label or functional assignment)
    ElementaryOperation elementary(parseElementaryOperation());
    switch (currentToken())
    {
    case Token::LParen:
    {
        Expression expr = parseCall(std::move(elementary));
        return ExpressionStatement{locationOf(expr), expr};
    }
    case Token::Comma:
    {
        // if a comma follows, a multiple assignment is assumed

        if (elementary.type() != typeid(assembly::Identifier))
            fatalParserError("Label name / variable name must precede \",\" (multiple assignment).");
        assembly::Identifier const& identifier = boost::get<assembly::Identifier>(elementary);

        Assignment assignment = createWithLocation<Assignment>(identifier.location);
        assignment.variableNames.emplace_back(identifier);

        do
        {
            expectToken(Token::Comma);
            elementary = parseElementaryOperation();
            if (elementary.type() != typeid(assembly::Identifier))
                fatalParserError("Variable name expected in multiple assignment.");
            assignment.variableNames.emplace_back(boost::get<assembly::Identifier>(elementary));
        }
        while (currentToken() == Token::Comma);

        expectToken(Token::Colon);
        expectToken(Token::Assign);

        assignment.value.reset(new Expression(parseExpression()));
        assignment.location.end = locationOf(*assignment.value).end;
        return assignment;
    }
    case Token::Colon:
    {
        if (elementary.type() != typeid(assembly::Identifier))
            fatalParserError("Label name / variable name must precede \":\".");
        assembly::Identifier const& identifier = boost::get<assembly::Identifier>(elementary);
        advance();
        // identifier:=: should be parsed as identifier: =: (i.e. a label),
        // while identifier:= (being followed by a non-colon) as identifier := (assignment).
        if (currentToken() == Token::Assign && peekNextToken() != Token::Colon)
        {
            assembly::Assignment assignment = createWithLocation<assembly::Assignment>(identifier.location);
            if (m_flavour != AsmFlavour::Yul && instructions().count(identifier.name.str()))
                fatalParserError("Cannot use instruction names for identifier names.");
            advance();
            assignment.variableNames.emplace_back(identifier);
            assignment.value.reset(new Expression(parseExpression()));
            assignment.location.end = locationOf(*assignment.value).end;
            return assignment;
        }
        else
        {
            // label
            if (m_flavour != AsmFlavour::Loose)
                fatalParserError("Labels are not supported.");
            Label label = createWithLocation<Label>(identifier.location);
            label.name = identifier.name;
            return label;
        }
    }
    default:
        if (m_flavour != AsmFlavour::Loose)
            fatalParserError("Call or assignment expected.");
        break;
    }
    if (elementary.type() == typeid(assembly::Identifier))
    {
        Expression expr = boost::get<assembly::Identifier>(elementary);
        return ExpressionStatement{locationOf(expr), expr};
    }
    else if (elementary.type() == typeid(assembly::Literal))
    {
        Expression expr = boost::get<assembly::Literal>(elementary);
        return ExpressionStatement{locationOf(expr), expr};
    }
    else
    {
        solAssert(elementary.type() == typeid(assembly::Instruction), "Invalid elementary operation.");
        return boost::get<assembly::Instruction>(elementary);
    }
}

assembly::Case Parser::parseCase()
{
    RecursionGuard recursionGuard(*this);
    assembly::Case _case = createWithLocation<assembly::Case>();
    if (m_scanner->currentToken() == Token::Default)
        m_scanner->next();
    else if (m_scanner->currentToken() == Token::Case)
    {
        m_scanner->next();
        ElementaryOperation literal = parseElementaryOperation();
        if (literal.type() != typeid(assembly::Literal))
            fatalParserError("Literal expected.");
        _case.value = make_shared<Literal>(boost::get<assembly::Literal>(std::move(literal)));
    }
    else
        fatalParserError("Case or default case expected.");
    _case.body = parseBlock();
    _case.location.end = _case.body.location.end;
    return _case;
}

assembly::ForLoop Parser::parseForLoop()
{
    RecursionGuard recursionGuard(*this);
    ForLoop forLoop = createWithLocation<ForLoop>();
    expectToken(Token::For);
    forLoop.pre = parseBlock();
    forLoop.condition = make_shared<Expression>(parseExpression());
    forLoop.post = parseBlock();
    forLoop.body = parseBlock();
    forLoop.location.end = forLoop.body.location.end;
    return forLoop;
}

assembly::Expression Parser::parseExpression()
{
    RecursionGuard recursionGuard(*this);
    // In strict mode, this might parse a plain Instruction, but
    // it will be converted to a FunctionalInstruction inside
    // parseCall below.
    ElementaryOperation operation = parseElementaryOperation();
    if (operation.type() == typeid(Instruction))
    {
        Instruction const& instr = boost::get<Instruction>(operation);
        // Disallow instructions returning multiple values (and DUP/SWAP) as expression.
        if (
            instructionInfo(instr.instruction).ret != 1 ||
            isDupInstruction(instr.instruction) ||
            isSwapInstruction(instr.instruction)
        )
            fatalParserError(
                "Instruction \"" +
                instructionNames().at(instr.instruction) +
                "\" not allowed in this context."
            );
        if (m_flavour != AsmFlavour::Loose && currentToken() != Token::LParen)
            fatalParserError(
                "Non-functional instructions are not allowed in this context."
            );
        // Enforce functional notation for instructions requiring multiple arguments.
        int args = instructionInfo(instr.instruction).args;
        if (args > 0 && currentToken() != Token::LParen)
            fatalParserError(string(
                "Expected '(' (instruction \"" +
                instructionNames().at(instr.instruction) +
                "\" expects " +
                to_string(args) +
                " arguments)"
            ));
    }
    if (currentToken() == Token::LParen)
        return parseCall(std::move(operation));
    else if (operation.type() == typeid(Instruction))
    {
        // Instructions not taking arguments are allowed as expressions.
        solAssert(m_flavour == AsmFlavour::Loose, "");
        Instruction& instr = boost::get<Instruction>(operation);
        return FunctionalInstruction{std::move(instr.location), instr.instruction, {}};
    }
    else if (operation.type() == typeid(assembly::Identifier))
        return boost::get<assembly::Identifier>(operation);
    else
    {
        solAssert(operation.type() == typeid(assembly::Literal), "");
        return boost::get<assembly::Literal>(operation);
    }
}

std::map<string, dev::solidity::Instruction> const& Parser::instructions()
{
    // Allowed instructions, lowercase names.
    static map<string, dev::solidity::Instruction> s_instructions;
    if (s_instructions.empty())
    {
        for (auto const& instruction: solidity::c_instructions)
        {
            if (
                instruction.second == solidity::Instruction::JUMPDEST ||
                solidity::isPushInstruction(instruction.second)
            )
                continue;
            string name = instruction.first;
            transform(name.begin(), name.end(), name.begin(), [](unsigned char _c) { return tolower(_c); });
            s_instructions[name] = instruction.second;
        }
    }
    return s_instructions;
}

std::map<dev::solidity::Instruction, string> const& Parser::instructionNames()
{
    static map<dev::solidity::Instruction, string> s_instructionNames;
    if (s_instructionNames.empty())
    {
        for (auto const& instr: instructions())
            s_instructionNames[instr.second] = instr.first;
        // set the ambiguous instructions to a clear default
        s_instructionNames[solidity::Instruction::SELFDESTRUCT] = "selfdestruct";
        s_instructionNames[solidity::Instruction::KECCAK256] = "keccak256";
    }
    return s_instructionNames;
}

Parser::ElementaryOperation Parser::parseElementaryOperation()
{
    RecursionGuard recursionGuard(*this);
    ElementaryOperation ret;
    switch (currentToken())
    {
    case Token::Identifier:
    case Token::Return:
    case Token::Byte:
    case Token::Address:
    {
        string literal;
        if (currentToken() == Token::Return)
            literal = "return";
        else if (currentToken() == Token::Byte)
            literal = "byte";
        else if (currentToken() == Token::Address)
            literal = "address";
        else
            literal = currentLiteral();
        // first search the set of instructions.
        if (m_flavour != AsmFlavour::Yul && instructions().count(literal))
        {
            dev::solidity::Instruction const& instr = instructions().at(literal);
            ret = Instruction{location(), instr};
        }
        else
            ret = Identifier{location(), YulString{literal}};
        advance();
        break;
    }
    case Token::StringLiteral:
    case Token::Number:
    case Token::TrueLiteral:
    case Token::FalseLiteral:
    {
        LiteralKind kind = LiteralKind::Number;
        switch (currentToken())
        {
        case Token::StringLiteral:
            kind = LiteralKind::String;
            break;
        case Token::Number:
            if (!isValidNumberLiteral(currentLiteral()))
                fatalParserError("Invalid number literal.");
            kind = LiteralKind::Number;
            break;
        case Token::TrueLiteral:
        case Token::FalseLiteral:
            kind = LiteralKind::Boolean;
            break;
        default:
            break;
        }

        Literal literal{
            location(),
            kind,
            YulString{currentLiteral()},
            {}
        };
        advance();
        if (m_flavour == AsmFlavour::Yul)
        {
            expectToken(Token::Colon);
            literal.location.end = endPosition();
            literal.type = YulString{expectAsmIdentifier()};
        }
        else if (kind == LiteralKind::Boolean)
            fatalParserError("True and false are not valid literals.");
        ret = std::move(literal);
        break;
    }
    default:
        fatalParserError(
            m_flavour == AsmFlavour::Yul ?
            "Literal or identifier expected." :
            "Literal, identifier or instruction expected."
        );
    }
    return ret;
}

assembly::VariableDeclaration Parser::parseVariableDeclaration()
{
    RecursionGuard recursionGuard(*this);
    VariableDeclaration varDecl = createWithLocation<VariableDeclaration>();
    expectToken(Token::Let);
    while (true)
    {
        varDecl.variables.emplace_back(parseTypedName());
        if (currentToken() == Token::Comma)
            expectToken(Token::Comma);
        else
            break;
    }
    if (currentToken() == Token::Colon)
    {
        expectToken(Token::Colon);
        expectToken(Token::Assign);
        varDecl.value.reset(new Expression(parseExpression()));
        varDecl.location.end = locationOf(*varDecl.value).end;
    }
    else
        varDecl.location.end = varDecl.variables.back().location.end;
    return varDecl;
}

assembly::FunctionDefinition Parser::parseFunctionDefinition()
{
    RecursionGuard recursionGuard(*this);
    FunctionDefinition funDef = createWithLocation<FunctionDefinition>();
    expectToken(Token::Function);
    funDef.name = YulString{expectAsmIdentifier()};
    expectToken(Token::LParen);
    while (currentToken() != Token::RParen)
    {
        funDef.parameters.emplace_back(parseTypedName());
        if (currentToken() == Token::RParen)
            break;
        expectToken(Token::Comma);
    }
    expectToken(Token::RParen);
    if (currentToken() == Token::Sub)
    {
        expectToken(Token::Sub);
        expectToken(Token::GreaterThan);
        while (true)
        {
            funDef.returnVariables.emplace_back(parseTypedName());
            if (currentToken() == Token::LBrace)
                break;
            expectToken(Token::Comma);
        }
    }
    funDef.body = parseBlock();
    funDef.location.end = funDef.body.location.end;
    return funDef;
}

assembly::Expression Parser::parseCall(Parser::ElementaryOperation&& _initialOp)
{
    RecursionGuard recursionGuard(*this);
    if (_initialOp.type() == typeid(Instruction))
    {
        solAssert(m_flavour != AsmFlavour::Yul, "Instructions are invalid in Yul");
        Instruction& instruction = boost::get<Instruction>(_initialOp);
        FunctionalInstruction ret;
        ret.instruction = instruction.instruction;
        ret.location = std::move(instruction.location);
        solidity::Instruction instr = ret.instruction;
        InstructionInfo instrInfo = instructionInfo(instr);
        if (solidity::isDupInstruction(instr))
            fatalParserError("DUPi instructions not allowed for functional notation");
        if (solidity::isSwapInstruction(instr))
            fatalParserError("SWAPi instructions not allowed for functional notation");
        expectToken(Token::LParen);
        unsigned args = unsigned(instrInfo.args);
        for (unsigned i = 0; i < args; ++i)
        {
            /// check for premature closing parentheses
            if (currentToken() == Token::RParen)
                fatalParserError(string(
                    "Expected expression (instruction \"" +
                    instructionNames().at(instr) +
                    "\" expects " +
                    to_string(args) +
                    " arguments)"
                ));

            ret.arguments.emplace_back(parseExpression());
            if (i != args - 1)
            {
                if (currentToken() != Token::Comma)
                    fatalParserError(string(
                        "Expected ',' (instruction \"" +
                        instructionNames().at(instr) +
                        "\" expects " +
                        to_string(args) +
                        " arguments)"
                    ));
                else
                    advance();
            }
        }
        ret.location.end = endPosition();
        if (currentToken() == Token::Comma)
            fatalParserError(string(
                "Expected ')' (instruction \"" +
                instructionNames().at(instr) +
                "\" expects " +
                to_string(args) +
                " arguments)"
            ));
        expectToken(Token::RParen);
        return ret;
    }
    else if (_initialOp.type() == typeid(Identifier))
    {
        FunctionCall ret;
        ret.functionName = std::move(boost::get<Identifier>(_initialOp));
        ret.location = ret.functionName.location;
        expectToken(Token::LParen);
        while (currentToken() != Token::RParen)
        {
            ret.arguments.emplace_back(parseExpression());
            if (currentToken() == Token::RParen)
                break;
            expectToken(Token::Comma);
        }
        ret.location.end = endPosition();
        expectToken(Token::RParen);
        return ret;
    }
    else
        fatalParserError(
            m_flavour == AsmFlavour::Yul ?
            "Function name expected." :
            "Assembly instruction or function name required in front of \"(\")"
        );

    return {};
}

TypedName Parser::parseTypedName()
{
    RecursionGuard recursionGuard(*this);
    TypedName typedName = createWithLocation<TypedName>();
    typedName.name = YulString{expectAsmIdentifier()};
    if (m_flavour == AsmFlavour::Yul)
    {
        expectToken(Token::Colon);
        typedName.location.end = endPosition();
        typedName.type = YulString{expectAsmIdentifier()};
    }
    return typedName;
}

string Parser::expectAsmIdentifier()
{
    string name = currentLiteral();
    if (m_flavour == AsmFlavour::Yul)
    {
        switch (currentToken())
        {
        case Token::Return:
        case Token::Byte:
        case Token::Address:
        case Token::Bool:
            advance();
            return name;
        default:
            break;
        }
    }
    else if (instructions().count(name))
        fatalParserError("Cannot use instruction names for identifier names.");
    expectToken(Token::Identifier);
    return name;
}

bool Parser::isValidNumberLiteral(string const& _literal)
{
    try
    {
        // Try to convert _literal to u256.
        auto tmp = u256(_literal);
        (void) tmp;
    }
    catch (...)
    {
        return false;
    }
    if (boost::starts_with(_literal, "0x"))
        return true;
    else
        return _literal.find_first_not_of("0123456789") == string::npos;
}