Suppose we have a problem:
$$\max_x f(x) \quad \text{s.t.} \quad g(x)\leq 0.$$
Assume $f$ and $g$ are both continuous. Assume now the following cases:
that $g(x)$ is not differentiable. We can assume what we like about $f$ though I'd prefer it to be as general as possible. If it is necessary, we can assume that $g$ is convex, or that it is piecewise differentiable.
That $f(x)$ is not differentiable. Again we can assume it is convex or piecewise differentiable.
What is the generic method for solving this for local/global maximum? If $f$ and $g$ were differentiable I'd have used the KKT method. But the KKT theorem doesn't apply because it assumes they are is (continuously) differentiable, at least at the optima I think.
Note that I am not looking for numerical methods. I am looking for an exact method that can produce a closed form solution at least in the cases where this is possible.