It’s a good question what the plans are for DP languages to handle situations where non-differentiability shouldn’t be ignored.

For sensitivity analysis it might be disastrous to conclude that an output is sensitive to an input when it is actually not, merely because an intermediary ReLU hit 0, for example.

A conservative approach could be to define versions of the relevant functions that threw exceptions at such points, or that also calculated the trusted margin of the resulting gradients; non-differentiability would then produce a zero trust margin.

he/she addressed that - the points at which the function isn't differentiable has measure zero. besides this isn't some kind of new hack - one sided limits (and therefore derivatives) were invented exactly for such cases (min, max, abs) and have been used by mathematicians probably since just about when calculus was invented.