Difference between revisions of "XCSG:Variable"
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| − | + | A Variable in XCSG is a named assignable entity. | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| + | The semantics of Variable are those common to all its subtypes. | ||
== Specifications == | == Specifications == | ||
{{Node | {{Node | ||
| − | | extends = | + | | extends = Node |
| − | | description = | + | | description = A named assignable entity that represents a portion of the system’s state. |
}} | }} | ||
| Line 18: | Line 15: | ||
{{XCSGTag | {{XCSGTag | ||
| − | | name = | + | | name = volatileVariable |
| description = Present if the code indicates the variable requires special treatment because the variable's value can be changed externally, e.g. by hardware. | | description = Present if the code indicates the variable requires special treatment because the variable's value can be changed externally, e.g. by hardware. | ||
}} | }} | ||
{{XCSGTag | {{XCSGTag | ||
| − | | name = | + | | name = happensBefore |
| description = Indicates that reading from the variable creates a "happens before" relationship to any code (in any thread) that previously wrote to the variable. | | description = Indicates that reading from the variable creates a "happens before" relationship to any code (in any thread) that previously wrote to the variable. | ||
| references = [http://docs.oracle.com/javase/specs/jls/se5.0/html/classes.html#8.3.1.4 JLS, SE 5.0: volatile fields] | | references = [http://docs.oracle.com/javase/specs/jls/se5.0/html/classes.html#8.3.1.4 JLS, SE 5.0: volatile fields] | ||
}} | }} | ||
| + | |||
| + | {{XCSGTag | ||
| + | | name = restrict | ||
| + | | description = Indicates a promise on the part of the programmer that the tagged [[Variable]] (which must be an instance of a [[Pointer]] type) is the only way to access the memory it points to; that is, that no other pointer will be used to alias the same range of memory, permitting the compiler to perform optimizations that would cause errors if the promise is not fulfilled. | ||
| + | }} | ||
| + | |||
| + | {{TaggedWithEnumeration | Visibility}} | ||
== Language mappings == | == Language mappings == | ||
| − | The <code>volatile</code> tag maps exactly to the <code>volatile</code> keyword in C and C++. Note that other languages, notably | + | The <code>volatile</code> tag maps exactly to the <code>volatile</code> keyword in C and C++. Note that other languages, notably Java (since 1.5), use the same keyword, but additionally require a memory barrier or "happens before" relationship between writes to the variable and later reads; for such variables, both the <code>volatile</code> and <code>memoryBarrier</code> tags should be present. |
Individual language mappings are provided for each subtype of Variable (Attribute, AssociationEnd, ArrayElement, Parameter, and LocalVariable). | Individual language mappings are provided for each subtype of Variable (Attribute, AssociationEnd, ArrayElement, Parameter, and LocalVariable). | ||
Latest revision as of 20:31, 9 December 2014
A Variable in XCSG is a named assignable entity.
The semantics of Variable are those common to all its subtypes.
Specifications
| Metaclass | Variable |
|---|---|
| Extends | Node |
| Description | A named assignable entity that represents a portion of the system’s state. |
| Direct Subkinds | CallInput, Field, ProgramVariable, StackVariable |
|---|
| All Superkinds | Node, ModelElement |
|---|
| Specified In Edges | |||
|---|---|---|---|
| In Edge | Predecessor | Multiplicity | Description |
| DataFlow (Edge) | DataFlow (Node) | ✱ | Connects DataFlow nodes to one another and to Variables, linking the origin of data to locations that it is modified or consumed. |
| Specified Out Edges | |||
|---|---|---|---|
| Out Edge | Successor | Multiplicity | Description |
| DataFlow (Edge) | DataFlow (Node) | ✱ | Connects DataFlow nodes to one another and to Variables, linking the origin of data to locations that it is modified or consumed. |
| DefinedAs | TypeAlias | 0..1 | Connects a Variable or DataFlow node which received its Type via a TypeAlias (such as a C/C++ typedef) to that TypeAlias. |
| InstanceVariableWritten | InstanceVariableAssignment | ✱ | Connects a value (DataFlow (Node) or Variable) representing an object instance to an InstanceVariableAssignment representing a write to a field of that object. |
| TypeOf | Type | 1 | Links a Variable or DataFlow node to its Type |
| Known Possible In Edges | ||||
|---|---|---|---|---|
| In Edge | Predecessor | Multiplicity | Description | |
| HasVariable | Namespace | 1 | Links a Classifier or Package to one of its Variables. | |
| InterproceduralDataFlow | Assignment | ✱ | Represents data flows between Functions, or involving Variables visible to multiple Functions.
| |
| Inherited From | In Edge | Predecessor | Multiplicity | Description |
| Node | Contains | Node | 1 | Indicates that the predecessor contains the successor in a sense specified by the specific type of Contains edge. |
| Known Possible Out Edges | ||||
|---|---|---|---|---|
| Out Edge | Successor | Multiplicity | Description | |
| InterproceduralDataFlow | DataFlow (Node) | ✱ | Represents data flows between Functions, or involving Variables visible to multiple Functions.
| |
| Inherited From | Out Edge | Successor | Multiplicity | Description |
| Node | Contains | Node | ✱ | Indicates that the predecessor contains the successor in a sense specified by the specific type of Contains edge. |
| Tag | immutable |
|---|---|
| Description | Present if the variable cannot be changed after initialization. |
| Tag | volatileVariable |
|---|---|
| Description | Present if the code indicates the variable requires special treatment because the variable's value can be changed externally, e.g. by hardware. |
| Tag | happensBefore |
|---|---|
| Description | Indicates that reading from the variable creates a "happens before" relationship to any code (in any thread) that previously wrote to the variable. |
| Tag | restrict |
|---|---|
| Description | Indicates a promise on the part of the programmer that the tagged Variable (which must be an instance of a Pointer type) is the only way to access the memory it points to; that is, that no other pointer will be used to alias the same range of memory, permitting the compiler to perform optimizations that would cause errors if the promise is not fulfilled. |
| Enumeration | Visibility |
|---|---|
| Description | The visibility of a Type, Variable, or Function in its Namespace. |
Language mappings
The volatile tag maps exactly to the volatile keyword in C and C++. Note that other languages, notably Java (since 1.5), use the same keyword, but additionally require a memory barrier or "happens before" relationship between writes to the variable and later reads; for such variables, both the volatile and memoryBarrier tags should be present.
Individual language mappings are provided for each subtype of Variable (Attribute, AssociationEnd, ArrayElement, Parameter, and LocalVariable).
