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Oracle Solaris 11.1 Dynamic Tracing Guide     Oracle Solaris 11.1 Information Library
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Document Information


1.  About DTrace

2.  D Programming Language

3.  Aggregations

4.  Actions and Subroutines

5.  Buffers and Buffering

6.  Output Formatting

7.  Speculative Tracing

Speculation Interfaces

Creating a Speculation

Using a Speculation

Committing a Speculation

Discarding a Speculation

Speculation Example

Speculation Options and Tuning

8.  dtrace(1M) Utility

9.  Scripting

10.  Options and Tunables

11.  Providers

12.  User Process Tracing

13.  Statically Defined Tracing for User Applications

14.  Security

15.  Anonymous Tracing

16.  Postmortem Tracing

17.  Performance Considerations

18.  Stability

19.  Translators

20.  Versioning


Using a Speculation

To use a speculation, an identifier returned from speculation must be passed to the speculate function in a clause before any data-recording actions. All subsequent data-recording actions in a clause containing a speculate will be speculatively traced. The D compiler will generate a compile-time error if a call to speculate follows data recording actions in a D probe clause. Therefore, clauses may contain speculative tracing or non-speculative tracing requests, but not both.

Aggregating actions, destructive actions, and the exit action may never be speculative. Any attempt to take one of these actions in a clause containing a speculate results in a compile-time error. A speculate may not follow a speculate: only one speculation is permitted per clause. A clause that contains only a speculate will speculatively trace the default action, which is defined to trace only the enabled probe ID. See Chapter 4, Actions and Subroutines for a description of the default action.

Typically, you assign the result of speculation to a thread-local variable and then use that variable as a subsequent predicate to other probes as well as an argument to speculate. For example:

        self->spec = speculation();

        printf("this is speculative");