On 25-apr-2006, at 16:46, Tom Lane wrote:
Paul van der Zwan <[EMAIL PROTECTED]> 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
That would be a clean solution ( and was suggested by some of my
colleagues as well)
However, I would argue that a system is pretty broken if it exposes
the
SHM_SHARE_MMU #define and then rejects it at runtime.
It is just a define, the fact that this define exists has nothing to
do with it having
any meaning. It's not like a HAVE_ISM flag. shmat() can fail for a
number of reasons, one of
them is not having ISM available on the current system.
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.
I disagree, I have no definite info why it is a hard failure,
probably because
there is no way to communicate to the app that it's request is
ignored. System calls
either fail or succeed. And introducing a new errno value just for
this is overkill, I guess.
regards, tom lane
Regards
Paul
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