[JdeBP]

It's a non-local goto, also a MetaWare language extension, out of the anonymous nested function that the for statement body becomes to (effectively) an anonymous label right after the for statement.

Another part of the High C/C++ Language Reference describes non-local labels and jumps to them. It doesn't go into great detail, but it does talk about stack unwinding, so expect something similar to how High C/C++ implemented throwing exceptions.