Type Members

1.  abstract type DomainIllegalValue <: IllegalValue with DomainValue

   Abstracts over the concrete type of IllegalValue.

   Abstracts over the concrete type of IllegalValue.

   This type needs to be refined whenever the class IllegalValue is refined or the type DomainValue is refined.

   Definition Classes

   ValuesDomain

2.  abstract type DomainReferenceValue >: Null <: ReferenceValue with DomainTypedValue[ReferenceType]

   Definition Classes

   ValuesDomain

3.  abstract type DomainReturnAddressValue <: ReturnAddressValue with DomainValue

   Abstracts over the concrete type of ReturnAddressValue.

   Abstracts over the concrete type of ReturnAddressValue. Needs to be fixed by some sub-trait/sub-class. In the simplest case (i.e., when neither the Value trait nor the ReturnAddressValue trait was refined) it is sufficient to write:

   type DomainReturnAddressValue = ReturnAddressValue

   Definition Classes

   ValuesDomain

4.  abstract type DomainReturnAddressValues <: ReturnAddressValues with DomainValue

   Definition Classes

   ValuesDomain

5.  abstract type DomainTypedValue[+T <: Type] >: Null <: DomainValue

   Definition Classes

   ValuesDomain

6.  abstract type DomainValue >: Null <: Value

   Abstracts over the concrete type of Value.

   Abstracts over the concrete type of Value. Needs to be refined by traits that inherit from Domain and which extend Domain's Value trait.

   Definition Classes

   ValuesDomain

7.  type ExceptionValue = DomainReferenceValue

   A simple type alias of the type DomainValue; used to facilitate comprehension.

   A simple type alias of the type DomainValue; used to facilitate comprehension.

   Definition Classes

   ValuesDomain

8.  type ExceptionValues = Iterable[ExceptionValue]

   A type alias for Iterables of ExceptionValues; used to facilitate comprehension.

   A type alias for Iterables of ExceptionValues; used to facilitate comprehension.

   Definition Classes

   ValuesDomain

9.  type Locals = collection.mutable.Locals[DomainValue]

   An instruction's current register values/locals are represented using an array.

   An instruction's current register values/locals are represented using an array.

   Definition Classes

   ValuesDomain

10.  type LocalsArray = Array[Locals]

    Definition Classes

    ValuesDomain

11.  type Operands = List[DomainValue]

    An instruction's operands are represented using a list where the first element of the list represents the top level operand stack value.

    An instruction's operands are represented using a list where the first element of the list represents the top level operand stack value.

    Definition Classes

    ValuesDomain

12.  type OperandsArray = Array[Operands]

    Definition Classes

    ValuesDomain

13.  class IllegalValue extends Value with IsIllegalValue

    Represents a value that has no well defined state/type.

    Represents a value that has no well defined state/type. Such values are either the result of a join of two incompatible values or if the variable was identified as being dead. IllegalValue's are only found in registers (in the locals).

    Attributes

    protected

    Definition Classes

    ValuesDomain

    See also

    org.opalj.ai.Domain.Value for further details.

14.  trait RETValue extends Value with IsReturnAddressValue

    Definition Classes

    ValuesDomain

15.  trait ReferenceValue extends TypedValue[ReferenceType] with IsReferenceValue

    Definition Classes

    ValuesDomain

16.  class ReturnAddressValue extends RETValue

    Stores a single return address (i.e., a program counter/index into the code array).

    Stores a single return address (i.e., a program counter/index into the code array).

    Definition Classes

    ValuesDomain

    Note

    Though the framework completely handles all aspects related to return address values, it is nevertheless necessary that this class inherits from Value as return addresses are stored on the stack/in the registers. However, if the Value trait should be refined, all additional methods may – from the point-of-view of OPAL-AI – just throw an UnsupportedOperationException as these additional methods will never be called by the OPAL-AI.

17.  class ReturnAddressValues extends RETValue

    A collection of (not further stored) return address values.

    A collection of (not further stored) return address values. Primarily used when we join the executions of subroutines.

    Definition Classes

    ValuesDomain

18.  trait TypedValue[+T <: Type] extends Value with KnownTypedValue

    Definition Classes

    ValuesDomain

19.  trait Value extends ValueInformation

    Abstracts over a concrete operand stack value or a value stored in one of the local variables/registers.

    Abstracts over a concrete operand stack value or a value stored in one of the local variables/registers.

    Use Of Value/Dependencies On Value

    In general, subclasses and users of a Domain should not have/declare a direct dependency on Value. Instead they should use DomainValue as otherwise extensibility of a Domain may be hampered or even be impossible. The only exceptions are, of course, classes that directly inherit from this class.

    Refining Value

    If you directly extend/refine this trait (i.e., in a subclass of the Domain trait you write something like trait Value extends super.Value), make sure that you also extend all classes/traits that inherit from this type (this may require a deep mixin composition and that you refine the type DomainType accordingly). However, OPAL was designed such that extending this class should – in general – not be necessary. It may also be easier to encode the desired semantics – as far as possible – as part of the domain.

    Implementing Value

    Standard inheritance from this trait is always supported and is the primary mechanism to model an abstract domain's lattice w.r.t. some special type of value. In general, the implementation should try to avoid creating new instances of values unless strictly required to model the domain's semantics. This will greatly improve the overall performance as this framework heavily uses reference-based equality checks to speed up the evaluation.

    Definition Classes

    ValuesDomain

    Note

    OPAL does not rely on any special equality semantics w.r.t. values and never directly or indirectly calls a Value's equals method. Hence, a domain can encode equality such that it best fits its need. However, some of the provided domains rely on the following semantics for equals: Two domain values have to be equal (==) iff they represent the same information. This includes additional information, such as, the value of the origin. E.g., a value (AnIntegerValue) that represents an arbitrary Integer value has to return true if the domain value with which it is compared also represents an arbitrary Integer value (AnIntegerValue). However, it may still be necessary to use multiple objects to represent an arbitrary integer value if, e.g., constraints should be attached to specific values. For example, after a comparison of an integer value with a predefined value (e.g., AnIntegerValue < 4) it is possible to constrain the respective value on the subsequent paths (< 4 on one path and >= 4 on the other path). To make that possible, it is however necessary to distinguish the AnIntegervalue from some other AnIntegerValue to avoid constraining unrelated values.

    public void foo(int a,int b) {
        if(a < 4) {
            z = a - 2 // here a is constrained (< 4), b and z are unconstrained
        }
        else {
            z = a + 2 // here a is constrained (>= 4), b and z are unconstrained
        }
    }

    In general, equals is only defined for values belonging to the same domain. If values need to be compared across domains, they need to be adapted to a target domain first.