unshared Variables

If a variable is marked as unshared, an instance of this variable is made available to every match site for a probe. The scope of this variable is limited to the specific match site. The value of this variable will be stable on each entry into the probe's logic, meaning that it will not be reinitialized each time.

This can be used to collect data at a specific program point over time.

For example:

wasm:opcode:call:before {
    // collect the number of times each `call` opcode is executed during dynamic execution.
    // (as many counts as there are `call` opcodes in the program)
    // This variable will not be reinitialized each time this probe's body is executed,
    // rather, it will be the value it was the last time it ran!
    unshared var count: i32;
    count++;
    
    // This variable will be reinitialized to 0 each time this probe's body is executed
    i32 local_variable;
    local_variable++;
}