LabVIEW programming elements
The main challenge in symbolic executing dataflow programs is assigning execution order to the instruction blocks. Since there is likely to be one or more parallel parts in the program, which have a non-deterministic execution order, converting them to a sequence of instructions is not a trivial question.
From the symbolic execution point of view, VIs (Virtual Instruments) can be treated as the program, on which the symbolic execution is done. It has inputs, outputs, and most of the instructions are usually the native components of LabVIEW (so that their behaviour can be predicted).
- Controls are going to be the inputs of our program. Their data type can be chosen as one of the basic types, clusters (similar to struct), or objects. In the case of symbolic execution, we are going to stick to the basic types.
- Indicators are the outputs of the program.
Instruction blocks use wires to pass data to each other. They are similar to variables in text-based languages, but they also define order of execution between blocks. Since each wire is going to represent a new variable in the program, the symbolic executor will have to deal with lots of unnamed variables.
This section will describe, how the native blocks of LabVIEW NXG will be planned or expected to behave during symbolic execution.
This palette contains the basic programming elements of LabVIEW.
The case structure will simply be interpreted as an IF statement, and loops can also be handled as an IF-GOTO structure. Most of the cases, for loops run a fixed number of iterations, which means there will be no symbolic variable in the loop condition.
TODO further investigation
TODO EVENT LOOP. Timer blocks can be ignored by symbolic execution most of the time.
Based on a boolean value, it passes the corresponding wire through. It will not be a forking statement, since both branches will be executed by the processing of the select block.
These will be the fix parameters of the program.
Basic math operations, like addition and subtraction will be easy to handle. Complex numbers can be treated as a struct. For Random Number block, we can assign a fix expected value, like 0.5 (or can be treated like an input).
These are basic string operations, like in any other programming language.
Like struct
Special cluster, with error information (error code, decription)
Mathematical functions
These are the same operations as in Data types.
These can be calculated, or approximated.
2D double array operations
Fitting, linear algebra, special functions, statistics, probability, interpolation, integral differentation, formula, geometry, BLAS, polynomial, optimization, ODE
I feel, implementing these would be too difficult for this project.
When possible, use an approximate value.
Black box, use expected vaules
Something like global variable, use expected value
Black box
Black box
Since it behaves like a global variable, they cannot be implemented in symbolic execution.
Black box
These might be handled as program inputs (which button is pressed)
???
Black box