solidity/libsolidity/formal/SMTEncoder.h

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/*
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/>.
*/
/**
* Encodes Solidity into SMT expressions without creating
* any verification targets.
* Also implements the SSA scheme for branches.
*/
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#pragma once
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#include <libsolidity/formal/EncodingContext.h>
#include <libsolidity/formal/SymbolicVariables.h>
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#include <libsolidity/formal/VariableUsage.h>
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#include <libsolidity/ast/ASTVisitor.h>
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#include <libsolidity/interface/ReadFile.h>
#include <liblangutil/ErrorReporter.h>
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#include <string>
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#include <unordered_map>
#include <vector>
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namespace langutil
{
class ErrorReporter;
struct SourceLocation;
}
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namespace dev
{
namespace solidity
{
class SMTEncoder: public ASTConstVisitor
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{
public:
SMTEncoder(smt::EncodingContext& _context);
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/// @returns the leftmost identifier in a multi-d IndexAccess.
static Expression const* leftmostBase(IndexAccess const& _indexAccess);
/// @returns the FunctionDefinition of a FunctionCall
/// if possible or nullptr.
static FunctionDefinition const* functionCallToDefinition(FunctionCall const& _funCall);
protected:
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// TODO: Check that we do not have concurrent reads and writes to a variable,
// because the order of expression evaluation is undefined
// TODO: or just force a certain order, but people might have a different idea about that.
bool visit(ContractDefinition const& _node) override;
void endVisit(ContractDefinition const& _node) override;
void endVisit(VariableDeclaration const& _node) override;
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bool visit(ModifierDefinition const& _node) override;
bool visit(FunctionDefinition const& _node) override;
void endVisit(FunctionDefinition const& _node) override;
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bool visit(PlaceholderStatement const& _node) override;
bool visit(IfStatement const& _node) override;
bool visit(WhileStatement const&) override { return false; }
bool visit(ForStatement const&) override { return false; }
void endVisit(VariableDeclarationStatement const& _node) override;
void endVisit(Assignment const& _node) override;
void endVisit(TupleExpression const& _node) override;
bool visit(UnaryOperation const& _node) override;
void endVisit(UnaryOperation const& _node) override;
bool visit(BinaryOperation const& _node) override;
void endVisit(BinaryOperation const& _node) override;
void endVisit(FunctionCall const& _node) override;
void endVisit(Identifier const& _node) override;
void endVisit(Literal const& _node) override;
void endVisit(Return const& _node) override;
bool visit(MemberAccess const& _node) override;
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void endVisit(IndexAccess const& _node) override;
void endVisit(IndexRangeAccess const& _node) override;
bool visit(InlineAssembly const& _node) override;
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void endVisit(Break const&) override {}
void endVisit(Continue const&) override {}
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/// Do not visit subtree if node is a RationalNumber.
/// Symbolic _expr is the rational literal.
bool shortcutRationalNumber(Expression const& _expr);
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void arithmeticOperation(BinaryOperation const& _op);
/// @returns _op(_left, _right) with and without modular arithmetic.
/// Used by the function above, compound assignments and
/// unary increment/decrement.
virtual std::pair<smt::Expression, smt::Expression> arithmeticOperation(
Token _op,
smt::Expression const& _left,
smt::Expression const& _right,
TypePointer const& _commonType,
Expression const& _expression
);
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void compareOperation(BinaryOperation const& _op);
void booleanOperation(BinaryOperation const& _op);
void initFunction(FunctionDefinition const& _function);
void visitAssert(FunctionCall const& _funCall);
void visitRequire(FunctionCall const& _funCall);
void visitGasLeft(FunctionCall const& _funCall);
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void visitTypeConversion(FunctionCall const& _funCall);
void visitFunctionIdentifier(Identifier const& _identifier);
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/// Encodes a modifier or function body according to the modifier
/// visit depth.
void visitFunctionOrModifier();
/// Defines a new global variable or function.
void defineGlobalVariable(std::string const& _name, Expression const& _expr, bool _increaseIndex = false);
/// Handles the side effects of assignment
/// to variable of some SMT array type
/// while aliasing is not supported.
void arrayAssignment();
/// Handles assignment to SMT array index.
void arrayIndexAssignment(Expression const& _expr, smt::Expression const& _rightHandSide);
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/// Division expression in the given type. Requires special treatment because
/// of rounding for signed division.
smt::Expression division(smt::Expression _left, smt::Expression _right, IntegerType const& _type);
void assignment(VariableDeclaration const& _variable, Expression const& _value);
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/// Handles assignments to variables of different types.
void assignment(VariableDeclaration const& _variable, smt::Expression const& _value);
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/// Handles assignments between generic expressions.
/// Will also be used for assignments of tuple components.
void assignment(
Expression const& _left,
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std::vector<smt::Expression> const& _right,
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TypePointer const& _type,
langutil::SourceLocation const& _location
);
/// Computes the right hand side of a compound assignment.
smt::Expression compoundAssignment(Assignment const& _assignment);
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/// Maps a variable to an SSA index.
using VariableIndices = std::unordered_map<VariableDeclaration const*, int>;
/// Visits the branch given by the statement, pushes and pops the current path conditions.
/// @param _condition if present, asserts that this condition is true within the branch.
/// @returns the variable indices after visiting the branch.
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VariableIndices visitBranch(ASTNode const* _statement, smt::Expression const* _condition = nullptr);
VariableIndices visitBranch(ASTNode const* _statement, smt::Expression _condition);
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using CallStackEntry = std::pair<CallableDeclaration const*, ASTNode const*>;
void initializeStateVariables(ContractDefinition const& _contract);
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void initializeLocalVariables(FunctionDefinition const& _function);
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void initializeFunctionCallParameters(CallableDeclaration const& _function, std::vector<smt::Expression> const& _callArgs);
void resetStateVariables();
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/// @returns the type without storage pointer information if it has it.
TypePointer typeWithoutPointer(TypePointer const& _type);
/// Given two different branches and the touched variables,
/// merge the touched variables into after-branch ite variables
/// using the branch condition as guard.
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void mergeVariables(std::set<VariableDeclaration const*> const& _variables, smt::Expression const& _condition, VariableIndices const& _indicesEndTrue, VariableIndices const& _indicesEndFalse);
/// Tries to create an uninitialized variable and returns true on success.
bool createVariable(VariableDeclaration const& _varDecl);
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/// @returns an expression denoting the value of the variable declared in @a _decl
/// at the current point.
smt::Expression currentValue(VariableDeclaration const& _decl);
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/// @returns an expression denoting the value of the variable declared in @a _decl
/// at the given index. Does not ensure that this index exists.
smt::Expression valueAtIndex(VariableDeclaration const& _decl, int _index);
/// Returns the expression corresponding to the AST node.
/// If _targetType is not null apply conversion.
/// Throws if the expression does not exist.
smt::Expression expr(Expression const& _e, TypePointer _targetType = nullptr);
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/// Creates the expression (value can be arbitrary)
void createExpr(Expression const& _e);
/// Creates the expression and sets its value.
void defineExpr(Expression const& _e, smt::Expression _value);
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/// Adds a new path condition
void pushPathCondition(smt::Expression const& _e);
/// Remove the last path condition
void popPathCondition();
/// Returns the conjunction of all path conditions or True if empty
smt::Expression currentPathConditions();
/// @returns a human-readable call stack. Used for models.
langutil::SecondarySourceLocation callStackMessage(std::vector<CallStackEntry> const& _callStack);
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/// Copies and pops the last called node.
CallStackEntry popCallStack();
/// Adds (_definition, _node) to the callstack.
void pushCallStack(CallStackEntry _entry);
/// Add to the solver: the given expression implied by the current path conditions
void addPathImpliedExpression(smt::Expression const& _e);
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/// Copy the SSA indices of m_variables.
VariableIndices copyVariableIndices();
/// Resets the variable indices.
void resetVariableIndices(VariableIndices const& _indices);
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/// @returns variables that are touched in _node's subtree.
std::set<VariableDeclaration const*> touchedVariables(ASTNode const& _node);
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/// @returns the VariableDeclaration referenced by an Identifier or nullptr.
VariableDeclaration const* identifierToVariable(Expression const& _expr);
/// Creates symbolic expressions for the returned values
/// and set them as the components of the symbolic tuple.
void createReturnedExpressions(FunctionCall const& _funCall);
/// @returns a note to be added to warnings.
std::string extraComment();
smt::VariableUsage m_variableUsage;
bool m_arrayAssignmentHappened = false;
// True if the "No SMT solver available" warning was already created.
bool m_noSolverWarning = false;
/// Stores the instances of an Uninterpreted Function applied to arguments.
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/// These may be direct application of UFs or Array index access.
/// Used to retrieve models.
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std::set<Expression const*> m_uninterpretedTerms;
std::vector<smt::Expression> m_pathConditions;
/// Local SMTEncoder ErrorReporter.
/// This is necessary to show the "No SMT solver available"
/// warning before the others in case it's needed.
langutil::ErrorReporter m_errorReporter;
langutil::ErrorList m_smtErrors;
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/// Stores the current function/modifier call/invocation path.
std::vector<CallStackEntry> m_callStack;
/// Returns true if the current function was not visited by
/// a function call.
bool isRootFunction();
/// Returns true if _funDef was already visited.
bool visitedFunction(FunctionDefinition const* _funDef);
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/// Depth of visit to modifiers.
/// When m_modifierDepth == #modifiers the function can be visited
/// when placeholder is visited.
/// Needs to be a stack because of function calls.
std::vector<int> m_modifierDepthStack;
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ContractDefinition const* m_currentContract = nullptr;
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/// Stores the context of the encoding.
smt::EncodingContext& m_context;
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};
}
}