Jan Schaumann via freebsd-net <freebsd-net@freebsd.org> wrote: > Konstantin Belousov <kostik...@gmail.com> wrote: > > On Tue, Nov 23, 2021 at 09:08:39PM -0500, Jan Schaumann via freebsd-net > > wrote: > > > > - Why does _any_ of those fail? > > > - Why does a.c succeed when compiled with clang, but > > > b.c does not? > > Most likely because you did not fully initialized *sin. > > > Really it is UB, try to memset(sin, 0, sizeof(*sin)). > > Nice, that works.
Specifically, it looks like it's the sin6_scope_id that matters here: In the case where we have additional stack variables, 'sin->sin6_scope_id' ends up being set to '0', while in the other case it retains a random value. The random value then means that we're trying to bind not "::1", but "::1%<value>", which is why this fails. Fun. -Jan
