Returning errno as a second value

[Luís Oliveira]

Felix Filozov <ffilozov at gmail.com> writes:

> Franz support has said that setting :errno-value is the only
> guaranteed way to get errno. Macros such as without-interrupt,
> without-scheduling, and with-delayed-interrupts, are not sufficient.

Cool, thanks. It'd be nice to know what the failure modes are so we can
write tests and bug other Lisp vendors about it.

Luís