> What practical patterns are enabled by TCO in C?

Continuation Passing Style - an important construction for interpreters, but which is also useful for compilers as it's a nice way to do control flow analysis, data flow analysis and more.

The missing feature is closures - functions which capture values from their static environment, which are basically needed to make CPS useful. GCC has nested functions, but they cannot capture without making the stack executable, which is terrible. There's a proposal[1] to get closures into C, but at present you need to simulate the capturing yourself, which is cumbersome, but can be done efficiently.

[1]:https://thephd.dev/_vendor/future_cxx/papers/C%20-%20Functio...