to my knowledge, they detect some common intentional and unintentional infinite loop patterns, but not much more:

    for(;;) // intentional

    for(unsigned i=10;i>=0;i--)
    for(int i=0;j<10;i++)
    for(unsigned i=0;i!=100;i+=8)
    // unintentional

in C infinite loops with no side effects are UB, so detecting them is useful for diagnostics.

guaranteed termination also is needed for some optimizations. but since side-effect-less infinite loops are UB in C, a compiler doesn't have to prove that such a loop terminates, it can just assume it does. other languages may differ, but I don't think any of them prove convergence of algorithms.

a don't-mind-the-recursion flag can be `-fno-finite-loops` on clang, or a read or write to a `volatile` variable in standard C.