Earlier quoted context omitted.
4. the machine that executes the code is ill-defined and will change far before the code you write is retired.
An program written in an ill-defined language being run by a malicious interpreter with an agenda would be a really interesting project in seeing how far you could twist the meaning of the original program.
There are some known issues of compilers eliding the zero-ing out of secret data. There is no portable way of enforcing this.