2.13.1 CONVERSE PseudoGlobals

Three classes of pseudoglobal variables are supported: node-private, process-private, and thread-private variables.

Node-private global variables

are specific to a node. They are shared among all the processes within the node.

Process-private global variables

are specific to a process. They are shared among all the threads within the process.

Thread-private global variables

are specific to a thread. They are truely private.

There are five macros for each class. These macros are for declaration, static declaration, extern declaration, initialization, and access. The declaration, static and extern specifications have the same meaning as in C. In order to support portability, however, the global variables must be installed properly, by using the initialization macros. For example, if the underlying machine is a simulator for the machine model supported by CONVERSE, then the thread-private variables must be turned into arrays of variables. Initialize and Access macros hide these details from the user. It is possible to use global variables without these macros, as supported by the underlying machine, but at the expense of portability.

Macros for node-private variables:

CsvDeclare(type,variable)
CsvStaticDeclare(type,variable)
CsvExtern(type,variable)
CsvInitialize(type,variable)
CsvAccess(variable)

Macros for process-private variables:

CpvDeclare(type,variable)
CpvStaticDeclare(type,variable)
CpvExtern(type,variable)
CpvInitialize(type,variable)
CpvAccess(variable)

Macros for thread-private variables:

CtvDeclare(type,variable)
CtvStaticDeclare(type,variable)
CtvExtern(type,variable)
CtvInitialize(type,variable)
CtvAccess(variable)

A sample code to illustrate the usage of the macros is provided in Figure 2.1. There are a few rules that the user must pay attention to: The type and variable fields of the macros must be a single word. Therefore, structures or pointer types can be used by defining new types with the typedef. In the sample code, for example, a struct point type is redefined with a typedef as Point in order to use it in the macros. Similarly, the access macros contain only the name of the global variable. Any indexing or member access must be outside of the macro as shown in the sample code (function func1). Finally, all the global variables must be installed before they are used. One way to do this systematically is to provide a module-init function for each file (in the sample code - ModuleInit(). The module-init functions of each file, then, can be called at the beginning of execution to complete the installations of all global variables.

Figure 2.1: An example code for global variable usage