Program Dependence Graph (PDG) Construction Quiz

To extract the part of the program that can affect the values computed at a given program point

System Dependency Graph (SDG)

Handling object-oriented programs in Java

Graphs do not produce complete slices for all types of programs

The object variables selected by the programmer

Handling linear dependence within sub-statements of programs

It leads to a loss of completeness in many cases.

To improve the completeness of program slices when an object variable is selected as the slicing criterion.

It is used for extracting statements that affect the value of a variable at a given program point.

To support polymorphism, dynamic binding, and inheritance.

They are not always complete, missing some code that can affect the slicing criterion.

The bug will remain undetected and may cause further issues.

To ensure that the slice computed from a variable produces specialized code equivalent to the original program.

The exclusion of some required data members from object variables.

The set of program variables whose value is accessed at statement n

When m post-dominates one but not all of n’s CFG successors

v is defined in node n and used in node m without being redefined in between

Parameter passing between method calls and definitions

By augmenting its representation to consider object-oriented programs

As separate trees for each possible dynamic type connected to the corresponding method definition

Infinite representation of object parameters

Augments its representation to consider OO programs.

Separate trees for each possible dynamic type connected to the corresponding method definition.

Infinite representation of object parameters.

When a statement modifies the object the variable points to, but not its data members

The DEF set contains the data member followed by the object variable itself

Data members of an object can only be accessed through a method call

To simplify the computation of flow dependence

It poses new difficulties in the computation of flow dependence

The DEF set is transformed into an ordered sequence with the data members defined first, followed by the caller object itself

An alias assignment occurs when two object variables point to different objects

When an object variable is defined through the return of a method call

Modifies at least one data member but not its reference

It poses new difficulties in flow dependence computation.

Data members can only be accessed through a method call.

Partial definitions occur when no variable is used after its definition, while total definitions include assignments through method returns.

It cannot produce complete slices for Java OO programs

Primitive variables

Multiple data members

When all its data members are defined by a constructor call

Only used and defined data members have a representation in the unfolding tree

Control dependence subtree of the selected object variable

Flow dependences of object variables

The order in which all data members are defined

All data members followed by the object variable

The DEF set includes both old and new memory locations

Define all data members of an object variable

Method call does not depend on any data member of object variable a1 to define data member x

Standard notion of flow dependence for objects

Replacing the current definition of flow dependence with three more accurate definitions

More concrete slicing criteria

DEF and USE sets

Program variables that are defined and used at this CFG node

The DEF and USE sets for every statement

To represent all possible execution paths of a method

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All program variables defined at that node

All variables used in the program at that node

To extract the part of the program that can affect the values computed at a given program point (slicing criterion).

The assumptions provide an incomplete slice in all cases, specifically when some object variables are selected as the slicing criterion.

The sets DEF, USE, and KILL need to be redefined to distinguish when object variables are totally or partially used or defined in method calls.

The standard definition is insufficient to capture the dependences between partial definitions of objects.

To deal with Java object-oriented programs and represent the System Dependence Graph (SDG).

The DEF set of a node in a CFG contains the set of program variables that are defined at the node.

The purpose is to extract from a program the set of statements that affect the value of a variable at a given program point, which is known as the slicing criterion.

The fundamental problem is incompleteness, where the slices contain less code than needed, leading to the exclusion of some code that can affect the slicing criterion.

The impact is that the slicing criterion includes the definition of the method and tracks down where the values of the data members come from.

The flow dependence is characterized by the fact that a node m is control dependent on a node n in the CFG.

The DEF set denotes the variables being defined at the node, while the USE set denotes the variables being used at the node.

The paper presents the extension of program representations with the addition of object-flow dependence as a solution to the problem.

The selection of an object variable as the slicing criterion is crucial for the definition of flow dependence.

Object variables in Java consist of data members and methods.

The SSLDG extends the model to accept object variables as the slicing criterion.

The purpose is to extend the representation to accept object variables as the slicing criterion.

The purpose is to obtain complete slices when an object variable is selected as the slicing criterion.

Program slicing is used to identify and extract relevant parts of a program for tasks such as debugging, software maintenance, and program specialization.

Control dependence and flow dependence

To connect the PDGs of all the methods of a program and simulate parameter passing between calls and definitions.

It defines a class entry node for each class, connected to the method Enter nodes of all its methods by class membership arcs.

It represents the caller and its defined and used data members as a tree.

To address the issue of potentially infinite tree representation when an object is represented recursively.

The static representation of the program needs to define both possibilities.

The object parameter is represented in the graph as a tree structure, with a subtree for each possible dynamic class.

The JSysDG represents the relationship with a tree representation, linking only data members inside each type tree.

It occurs when a variable v is in DEF(n), v is in USE(m), and there exists a control-flow path from n to m where v is not redefined.

To accurately represent the dependence between objects and their data members in the program.

When an object variable is redefined with only some of its data members, leaving others unchanged.

The potential for infinite tree representation when an object is represented recursively.

primitive variables

An object variable v that points to a memory location m1 is totally defined in a program statement s if the execution of s makes v to point to m2, and m1 is not equal to m2.

The ordered sequence DEF os includes all the data members being defined first, and the object variable is defined at the end.

The main problem is that a statement may modify only some of the data members of an object variable, leading to partial definitions being split into different statements.

The JSysDG can produce incomplete slices, leading to limitations in accurately representing Java OO programs.

The JSysDG assumes that when an object variable is the caller of a method call, only the used and defined data members of the object have a representation in the unfolding tree as argument-in and argument-out nodes respectively.

The standard notion of flow dependence needs to be extended for the case of objects in order to solve the identified problem.

The paper presents the need to extend the standard notion of flow dependence for the case of objects in order to solve the identified problem.

The purpose of the JSysDG is to accurately represent the dependencies and flow of object-oriented programs, allowing for the computation of program slices.

The object variable is considered to be totally defined in that program statement, according to the definition provided in the text.

Program slicing is significant in helping with software maintenance, debugging, and program specialization by allowing developers to focus on specific parts of the code that are relevant to the task at hand.

The slicing criterion is a set of program statements and predicates that might affect the value of a program variable v that is defined or used at a program point p; (p, v) is known as the slicing criterion.

DEF os (#13) = [a1.x, a1. y , a1]

∅

When a statement modifies at least one data member of an object variable, but not the object it points to.

A method call that defines a data member of the caller, and an assignment of an object variable’s data member.

An ordered sequence that contains the data member followed by the object variable itself.

It allows differentiation of the specific moment in which a data member and an object is defined or used, and allows slicing a program with respect to a specific instant in the computation.

It allows differentiation of the specific moment in which a data member and an object is defined or used, and thus allows slicing a program with respect to a specific instant in the computation.

It provides an enhanced graph representation for object variables at the scope of a method call.

The standard definition is insufficient to account for the partial definition of an object variable.

The computation of the usual flow dependence encounters difficulties due to the partial definition of an object variable.

They represent the value of the object variable before and after the call, including the data members used or defined inside the function call.

The differentiation of the specific moment in which a data member and an object is defined or used.

The JSysDG addresses the problem of representing objects recursively and dealing with object variables that can be partially defined or used in a statement.

The incremental evolution from CFG to JSysDG aims to properly represent the program in order to automatically obtain the desired slice.

For an assignment of an object variable’s data member, the DEF set turns into the set of variables that are defined at that statement.

The new method is significant for distinguishing when object variables are being totally or partially used or defined in method calls.

The main limitation of JSysDG is its incompleteness when slicing an object that is the caller of a method call.

The JSysDG aims to solve the problem of representing object variables and their dependencies accurately in method calls.

When an assignment statement makes an object variable point to a different memory location, the dependencies and definitions of the object variable may change.

The purpose of extending the representations with the addition of object-flow dependence is to accurately capture the flow of object variables and their dependencies.

Program slicing is significant for understanding and analyzing the impact and dependencies of specific parts of a program, which is crucial for software maintenance, debugging, and program specialization.

A method call that defines some or all of the data members of the caller can impact the dependencies and definitions of the caller object variable.

The paper presents an approach that solves the problem by replacing the current definition of flow dependence with more accurate definitions for object variables.

The ordered sequence of definitions for an object variable includes the standard definition for primitive variables and a pair of new definitions for object variables called object-flow dependence and object-reference dependence.

To extract the part of the program that can affect the values computed at a given program point.

It leads to a scenario where the slice obtained by JSysDG is not complete when selecting some object variables as the slicing criterion.

The slices obtained from JSysDG do not produce complete slices in all cases, specifically when some object variables are selected as the slicing criterion.

The main limitation is that JSysDG does not produce complete slices in all cases, particularly when certain object variables are chosen as the slicing criterion.

The incompleteness result proves that the graphs used in program slicing do not produce complete slices in all cases, especially when some object variables are selected as the slicing criterion.

ClDG enhances the SDG representation by dealing with class-level dependencies, such as static method calls and static data members.

To extract from a program the set of statements that affect the value of a variable at a given program point.

The representation of dependences between partial definitions of objects is ill-defined, leading to a loss of completeness.

The set of statements in the program that affect the value of the selected object variable at a given program point.

JSysDG is not prepared to select an object variable as the slicing criterion, and it can produce a slice where only some of its required data members are included.

To introduce a program slicing technique for object-oriented programs based on the new program representation.

It allows for a more accurate flow representation between object variables and their data members.

The JSysDG is not prepared to select an object variable as the slicing criterion, leading to incompleteness in the computed slices.

The minimal slice of the code in Fig. 1a has been computed with the JSysDG.

A specific flow dependence for object type variables called object-flow dependence is added to the representations.

It leads to a loss of completeness in many cases.

Completeness is a fundamental property required by most applications of program slicing.

The purpose is to extract the set of statements that affect the value of a variable at a given program point.

The purpose of JSysDG is to represent polymorphic calls and dynamic binding.

Node m is control dependent on node n if m post-dominates one but not all of n’s CFG successors.

ClDG represents class entry nodes for each class, connected to method Enter nodes and data membership arcs.

JSysDG aims to represent polymorphic calls and dynamic binding, addressing the challenges of polymorphic objects and method calls with polymorphic parameters.

Program slicing is significant in identifying and isolating relevant parts of a program, aiding in software maintenance, debugging, and program specialization.

The ordered sequence DEF os for an object variable includes the variables that define its data members.

Flow dependence occurs when a variable v is defined in node n, used in node m, and there exists a control-flow path from n to m where v is not redefined.

When an assignment statement changes the reference of an object variable, it affects the control and flow dependences associated with the object variable.

Partial definitions of object variables occur when only some of the data members of an object variable are defined, leading to incomplete information about the object.

Liang and Harrold's assumptions lead to the DEF set including a tree structure representing each possible dynamic class and its data members.

The main limitation of JSysDG is the potential for infinite tree representation when objects are represented recursively.

The purpose of program slicing is to identify and extract relevant parts of a program based on a slicing criterion, aiding in program analysis and understanding.

When an object variable is the caller of a method call, only the used and defined data members of the object have a representation in the unfolding tree as argument-in and argument-out nodes respectively.

The DEF set for this statement includes the object variable itself and all its data members, and the order in which all these definitions occur is crucial for the definition of flow dependence.

The flow dependences of object variables need to be redefined so that slices are correctly computed when a whole object variable is selected as the slicing criterion.

The flow dependence between nodes n and m in a CFG is based on the set of program statements and predicates that might affect the value of a program variable v that is defined or used at a program point p.

Object variables in Java consist of a collection of data members, where each data member can be a primitive variable or another object variable.

The standard notion of flow dependence for the case of objects needs to be extended.

The DEF set includes the object variable itself and all its data members, while the USE set denotes the program statements and predicates that might affect the value of a program variable v that is defined or used at a program point p.

When a variable cannot be used without being previously defined in Java, it leads to a flow dependence between the definition and use of that variable.

The purpose of SSLDG is to annotate definitions and uses of object variables in program statements, particularly for the case of objects.

Primitive variables are always defined and used atomically in Java.

The new method is significant for extending the standard notion of flow dependence for the case of objects, as it allows for a more accurate description of the DEF and USE sets when object variables are contained inside them.

The purpose of program slicing is to obtain a set of program statements and predicates that might affect the value of a program variable, based on a slicing criterion.

The three more accurate definitions are: the standard definition of flow dependence for primitive variables, object-flow dependence, and object-reference dependence.

The 'defined variables (DEF)' and 'used variables (USE)' sets of each statement are specialized.

The purpose is to properly represent the program and automatically obtain the desired slice.

A node m is control dependent on a node n in a CFG if the execution of n influences the possible execution of m.

The impact is that the JSysDG slice may become incomplete, leading to missing data members and even method calls like the constructor.

The DEF and USE sets for every statement need to be redefined to properly represent definitions and uses of object variables and their data members.

The main problem is that the usual flow dependence was designed for variables that are atomically defined or used in a single statement, and it has not been reconsidered to deal with object variables that can be partially defined or used.

The 'defined variables (DEF)' set contains the program variables that are defined at the statement, while the 'used variables (USE)' set contains the program variables that are used at the statement.

The JSysDG assumes that the data members of an object are atomically defined or used in a single statement.

The purpose of SSLDG is to extend the theoretical model proposed by JSysDG to accept more concrete slicing criteria.

The main limitation is the incompleteness problem when slicing an object that is the caller of a method call, resulting in incomplete slices.

A partial definition involves defining or using only one of its data members in a statement.

Polymorphic calls and dynamic binding are represented as nodes in the JSysDG.

The extension JSysDG deals with representing objects recursively.

The JSysDG addresses the issue of incompleteness when representing objects recursively.

The paper presents the incompleteness result of representing objects recursively.

In Java, a variable cannot be used without being previously defined.

The DEF set denotes the definitions while the USE set denotes the uses at each CFG node.

The ClDG represents the dependencies between classes in an Object-Oriented program.

The representations need to be extended to solve the problem identified in the previous section.

The ordered sequence of definitions for an object variable in the mentioned statement is DEF os (#13) = [a1.x, a1. y , a1].

The impact is that the DEF set is transformed into an ordered sequence, including all the data members defined inside the method followed by the object variable itself.

In the scenario where no variable is used, the USE set equals to ∅ (empty set).

Program slicing is significant in various disciplines such as software maintenance, debugging, and program specialization as it allows for the extraction of relevant portions of a program.