Re: BUG #2406: Not all systems support SHM_SHARE_MMU - Mailing list pgsql-bugs

Paul van der Zwan <Paul.Vanderzwan@Sun.COM> writes:
> AFAIK getpagesizes() appeared in 2001 so that probably means it is
> missing in anything before Solaris 9.

We could handle this without relying on getpagesizes() by just trying
and falling back:

#ifdef SHM_SHARE_MMU
    memAddress = shmat(shmid, addr, SHM_SHARE_MMU);
    if (memAddress == (void *) -1 && errno == EINVAL)
        memAddress = shmat(shmid, addr, 0);
#else
    memAddress = shmat(shmid, addr, 0);
#endif

However, I would argue that a system is pretty broken if it exposes the
SHM_SHARE_MMU #define and then rejects it at runtime.

> I'll see if I can get the x86 experts here to have a look at it...

I think either Solaris/x86 should not expose this #define, or it should
silently ignore the bit at runtime.  AFAICS, SHM_SHARE_MMU has no
guaranteed semantic effect anyway, it's just a performance hint; so
ignoring it on platforms that can't handle it is reasonable.

            regards, tom lane