Stephen Frost <> writes:
> I'm going to guess this idea is a non-starter, but any hope there's some
> other system call which would tell us we're on a platform where
> shm_open() will hit us with SIGSYS?  What happens when shm_unlink() is
> called on this platform?  Or mmap()?

For context's sake, the machine does have mmap().  shm_open and shm_unlink
exist in libc and have declarations in <sys/mman.h>, but at least the
former traps with a signal, suggesting the kernel hasn't got support for

I agree with Robert that it's odd and obnoxious that the call doesn't just
return with errno = ENOSYS.  However, looking in the archives turns up
this interesting historical info:

I wonder whether, if we went back to blocking SIGSYS, we could expect that
affected calls would return ENOSYS (clearly preferable), or if that would
just lead to some very strange behavior.  Other archive entries mention
that you get SIGSYS on Cygwin if the Cygwin support daemon isn't running,
so that's at least one place where we'd want to check the behavior.

                        regards, tom lane

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