Tom Lane escribió:
> Andrew Dunstan <andrew@dunslane.net> writes:
> > Not quite out of the woods yet. We're getting this regression failure on
> > Windows/MSVC (see
> > <http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=bowerbird&dt=2014-01-17%2018%3A20%3A35>):
>
> > SELECT test_shm_mq(32768, (select string_agg(chr(32+(random()*96)::int), '') from generate_series(1,400)),
10000,1);
> > ! ERROR: queue size must be at least 472262143 bytes
>
> It looks like this is computing a bogus value:
>
> const Size shm_mq_minimum_size =
> MAXALIGN(offsetof(shm_mq, mq_ring)) + MAXIMUM_ALIGNOF;
>
> I seem to recall that we've previously found that you have to write
>
> MAXALIGN(offsetof(shm_mq, mq_ring[0])) + MAXIMUM_ALIGNOF;
>
> to keep MSVC happy with a reference to an array member in offsetof.
Hmm, this seems to contradict what's documented at the definition of
FLEXIBLE_ARRAY_MEMBER:
/* Define to nothing if C supports flexible array members, and to 1 if it does not. That way, with a declaration like
`structs { int n; double d[FLEXIBLE_ARRAY_MEMBER]; };', the struct hack can be used with pre-C99 compilers. When
computingthe size of such an object, don't use 'sizeof (struct s)' as it overestimates the size. Use 'offsetof (struct
s,d)' instead. Don't use 'offsetof (struct s, d[0])', as this doesn't work with MSVC and with C++ compilers. */
#define FLEXIBLE_ARRAY_MEMBER /**/
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
