In article <199902110336.TAA08878@lestat.nas.nasa.gov>
thorpej@nas.nasa.gov writes:

> Anyhow, a0 is a scratch register, and the ABI doesn't guarantee that it
> will be preserved in a longjmp(), etc.  However, during _signal_ delivery,
> and genuine _signal return_ (i.e. not longjmp()'s use of sigreturn to
> restore the context), __a0 must be preserved__, else programs could break.

Well, I understand user registers including scratch [ad][01] are restored
from the signal stack on signal return.
They are unmodified (restored by user land code) on longjmp, though.

Do I misunderstand something?
--
ITOH, Yasufumi <yasufu-i@is.aist-nara.ac.jp>, <itohy@netbsd.org>