The Language

Whamm enables tool implementers to express their instrumentation in terms of program events and corresponding predicated actions; "When this event occurs during program execution, do these actions if this predicate (or conditional) evaluates to true." This abstraction provides a high-level and intuitive syntax that can target events at various granularities in the target program.

Read on for an overview of the syntax and semantics of the language.

Language Concepts

• Variables are used to store data.
• Logical operations can be used to combine boolean expressions.
• Ternary Expressions can be used for succinct conditional variable assignments.
• Primitive types are numbers, booleans, and strings.
• Various arithmetic operations can be used with numbers.
• Strings are key for dealing with text, etc.
• Tuples allow using multiple values where one value is expected.
• Maps are key for storing large amounts of data, but they're implemented quite differently in Whamm.
• Function definitions can be used to reuse code snippets.
• Conditionals are if/else/elif statements used for simple control flow.
• Type Bounds are for dealing with polymorphic opcodes.
• Whamm also provides helpful features to enable instrumentation expressiveness.
  • Report variables are key for flushing the dynamic data collected by instrumentation during an application's run.
  • Unshared variables are used to create an instance of a variable per probe match-site whose value is retained across site visits.
  • Shared variables are used to create an instance of a variable that is shared by every probe match-site.
  • Frame variables are used to create an instance of a variable that is stored on a function's active frame.
• And finally, probes are used to express instrumentation.
• All of this syntax is used to write Whamm scripts.