The sequence of instructions given above is incorrect, it does not detect integer overflow (i.e. signed integer overflow). It detects carry, which is something else.

The correct sequence, which can be found in the official RISC-V documentation, requires more instructions.

Not checking for overflow in C programs is a serious mistake. All decent C compilers have compilation options for enabling checking for overflow. Such options should always be used, with the exception of the functions that have been analyzed carefully by the programmer and the conclusion has been that integer overflow cannot happen.

For example with operations involving counters or indices, overflow cannot normally happen, so in such places overflow checking may be disabled.