Package it.unive.lisa.program.cfg.statement.string

Class Length

java.lang.Object

it.unive.lisa.program.cfg.statement.Statement

it.unive.lisa.program.cfg.statement.Expression

it.unive.lisa.program.cfg.statement.NaryExpression

it.unive.lisa.program.cfg.statement.UnaryExpression

it.unive.lisa.program.cfg.statement.string.Length

All Implemented Interfaces:

ProgramPoint, CodeElement, Node<Statement,Edge,CFG>, java.lang.Comparable<Statement>

public class Length
extends UnaryExpression

An expression modeling the string length operation. The type of the operand must be StringType. The type of this expression is the Int32.

Since in most languages string operations are provided through calls to library functions, this class contains a field originating whose purpose is to optionally store a Statement that is rewritten to an instance of this class (i.e., a call to a NativeCFG modeling the library function). If present, such statement will be used as ProgramPoint for semantics computations. This allows subclasses to implement PluggableStatement easily without redefining the semantics provided by this class.

Field Summary

Fields

Modifier and Type	Field	Description
protected Statement	originating	Statement that has been rewritten to this operation, if any.

Fields inherited from class it.unive.lisa.program.cfg.statement.Statement

offset

Constructor Summary

Constructors

Constructor	Description
Length(CFG cfg, CodeLocation location, Expression parameter)	Builds the length.

Method Summary

Modifier and Type	Method	Description
protected <A extends AbstractState<A,H,V,T>,H extends HeapDomain<H>,V extends ValueDomain<V>,T extends TypeDomain<T>> AnalysisState<A,H,V,T>	unarySemantics(InterproceduralAnalysis<A,H,V,T> interprocedural, AnalysisState<A,H,V,T> state, SymbolicExpression expr, StatementStore<A,H,V,T> expressions)	Computes the semantics of the expression, after the semantics of the sub-expression has been computed.

Methods inherited from class it.unive.lisa.program.cfg.statement.UnaryExpression

expressionSemantics, getSubExpression

Methods inherited from class it.unive.lisa.program.cfg.statement.NaryExpression

accept, equals, getConstructName, getOrder, getStatementEvaluatedBefore, getSubExpressions, hashCode, semantics, setOffset, toString

Methods inherited from class it.unive.lisa.program.cfg.statement.Expression

getMetaVariables, getParentStatement, getRootStatement, getStaticType, setParentStatement

Methods inherited from class it.unive.lisa.program.cfg.statement.Statement

compareTo, getCFG, getEvaluationPredecessor, getLocation, getOffset, stopsExecution, throwsError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

originating

protected Statement originating

Statement that has been rewritten to this operation, if any. This is to accomodate the fact that, in most languages, string operations are performed through calls, and one might want to provide the semantics of those calls through NativeCFG that rewrites to instances of this class.

Constructor Detail

Length

public Length(CFG cfg,
              CodeLocation location,
              Expression parameter)

Builds the length.

Parameters:

cfg - the CFG where this operation lies

location - the code location where this operation is defined

parameter - the operand of this operation

Method Detail

unarySemantics

protected <A extends AbstractState<A,H,V,T>,H extends HeapDomain<H>,V extends ValueDomain<V>,T extends TypeDomain<T>> AnalysisState<A,H,V,T> unarySemantics(InterproceduralAnalysis<A,H,V,T> interprocedural,
                                                                                                                                                                                                                  AnalysisState<A,H,V,T> state,
                                                                                                                                                                                                                  SymbolicExpression expr,
                                                                                                                                                                                                                  StatementStore<A,H,V,T> expressions)
                                                                                                                                                                                                           throws SemanticException

Description copied from class: UnaryExpression

Computes the semantics of the expression, after the semantics of the sub-expression has been computed. Meta variables from the sub-expression will be forgotten after this expression returns.

Specified by:

unarySemantics in class UnaryExpression

Type Parameters:

A - the type of AbstractState

H - the type of the HeapDomain

V - the type of the ValueDomain

T - the type of TypeDomain

Parameters:

interprocedural - the interprocedural analysis of the program to analyze

state - the state where the expression is to be evaluated

expr - the symbolic expressions representing the computed value of the sub-expression of this expression

expressions - the cache where analysis states of intermediate expressions are stored and that can be accessed to query for post-states of parameters expressions

Returns:

the AnalysisState representing the abstract result of the execution of this expression

Throws:

SemanticException - if something goes wrong during the computation