Re: Dynamic Shared Memory stuff

On Sat, Apr 12, 2014 at 1:32 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Wed, Apr 9, 2014 at 9:20 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Wed, Apr 9, 2014 at 7:41 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>> I am just not sure whether it is okay to rearrange the code and call
>>> GetLastError() only if returned handle is Invalid (NULL) or try to look
>>> for more info.
>>
>> Well, I don't know either. You wrote the Windows portion of this
>> code, so you'll have to decide what's best. If the best practice in
>> this area is to only call GetLastError() if the handle isn't valid,
>> then that's probably what we should do, too. But I can't speak to
>> what the best practice is.
>
> I have checked that other place in code also check handle to
> decide if API has failed. Refer function PGSharedMemoryIsInUse().
> So I think fix to call GetLastError() after checking handle is okay.
> Attached patch fixes this issue. After patch, the server shows below
> log which is exactly what is expected from test_shm_mq

In PostgreSQL code, hmap == NULL, rather than !hmap, is the preferred
way to test for a NULL pointer. I notice that the !hmap style is used
throughout this code, so I guess cleaning that up is a matter for a
separate commit.

For the create case, I'm wondering if we should put the block that
tests for !hmap *before* the _dosmaperr() and check for EEXIST. What
is your opinion?

--
Robert Haas
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