Add option(s) to override provable relationships

In my contract I have a relationship where each user is storing their proportion of a total quantity. Due to a provable mathematical relationship between the quantities (I increase total every time I increase mine, and I decrease total every time I decrease mine), I can maintain an invariant in my code with more minimal input validation.

How would I add comments to my code to request mythril ignore specific violations that I could provable demonstrate are invariant?

Example contract:

contract A {
  uint total;
  mapping (address => uint) mine;

  function add()
    public
  {
    require( total + 1 > total ); // Overflow protection
    // require( mine[msg.sender] <= total ); // This should be necessary to avoid integer overflow
    total += 1;
    mine[msg.sender] += 1; // Curiously, no integer overflow raised here...
  }

  function subtract()
    public
  {
    require( mine[msg.sender] > 0 ); // Underflow protection
    // require( mine[msg.sender] <= total ); // This avoids throwing integer underflow
    total -= 1; // mythril throws an integer underflow here
    mine[msg.sender] -= 1; // @myth-ignore UNDERFLOW - Example of syntax
  }
}

Some tools have a @ignore CHECK_NAME comment that can be added to a line to ignore a specific check. I could save a bit of gas by just being able to avoid having a assert(mine <= total) in my code in two spots

[JoranHonig]

Adding invariants and statements to be proved is discussed in #405

Adding constraints to inform Mythril of possible invariants in order to prune & resolve false positives is not necessary anymore as Mythril now has a constrained memory model (vs the old unconstrained one)

Therefore I’m closing this issue if there is anything that isn’t captured in the other issue yet. Please open another issue so we can look at that separately

[rocky]

A very good idea, I think. I recently noticed in one of Suhabe’s benchmarks this:

 //No underflow because of credit/balance invariant: sum (credit.values) = balance

How do people feel about this variation: in a front-end wrapper, look for comments of the form:

//invariant: sum (credit.values) = balance

And add that as a constraint to the z3 solver. Presumably this would previent Mythril from triggering the violation.

Outside of a wrapper a --constraint option could be supplied.