tree 9559680400635982c454e54a648d2627758dae04
parent 43e7efb46555f13a556d92944ac05c19b8929b60
author Rich Felker <dalias@aerifal.cx> 1551801735 -0500
committer Rich Felker <dalias@aerifal.cx> 1551802126 -0500

don't reject unknown/future flags in sigaltstack, allow SS_AUTODISARM

historically, and likely accidentally, sigaltstack was specified to
fail with EINVAL if any flag bit other than SS_DISABLE was set. the
resolution of Austin Group issue 1187 fixes this so that the
requirement is only to fail for SS_ONSTACK (which cannot be set) or
"invalid" flags.

Linux fails on the kernel side for invalid flags, but historically
accepts SS_ONSTACK as a no-op, so it needs to be rejected in userspace
still.

with this change, the Linux-specific SS_AUTODISARM, provided since
commit 9680e1d03a794b0e0d5815c749478228ed40a36d but unusable due to
rejection at runtime, is now usable.