Properly check for readdir/closedir() failures

Clear errno before calling readdir() and handle old MinGW errno bug
while adding full test coverage for readdir/closedir failures.

Backpatch through 8.4.
Fix typos in pg_basebackup documentation

Joshua Tolley
Don't forget to flush XLOG_PARAMETER_CHANGE record.

Backpatch to 9.0 where XLOG_PARAMETER_CHANGE record was instroduced.
Fix refcounting bug in PLy_modify_tuple().

We must increment the refcount on "plntup" as soon as we have the
reference, not sometime later.  Otherwise, if an error is thrown in
between, the Py_XDECREF(plntup) call in the PG_CATCH block removes a
refcount we didn't add, allowing the object to be freed even though
it's still part of the plpython function's parsetree.

This appears to be the cause of crashes seen on buildfarm member
prairiedog.  It's a bit surprising that we've not seen it fail repeatably
before, considering that the regression tests have been exercising the
faulty code path since 2009.

The real-world impact is probably minimal, since it's unlikely anyone would
be provoking the "TD["new"] is not a dictionary" error in production, and
that's the only case that is actually wrong.  Still, it's a bug affecting
the regression tests, so patch all supported branches.

In passing, remove dead variable "plstr", and demote "platt" to a local
variable inside the PG_TRY block, since we don't need to clean it up
in the PG_CATCH path.
Document platform-specificity of unix_socket_permissions.

Back-patch to 8.4 (all supported versions).
Secure Unix-domain sockets of "make check" temporary clusters.

Any OS user able to access the socket can connect as the bootstrap
superuser and in turn execute arbitrary code as the OS user running the
test.  Protect against that by placing the socket in the temporary data
directory, which has mode 0700 thanks to initdb.  Back-patch to 8.4 (all
supported versions).  The hazard remains wherever the temporary cluster
accepts TCP connections, notably on Windows.

Attempts to run "make check" from a directory with a long name will now
fail.  An alternative not sharing that problem was to place the socket
in a subdirectory of /tmp, but that is only secure if /tmp is sticky.
The PG_REGRESS_SOCK_DIR environment variable is available as a
workaround when testing from long directory paths.

As a convenient side effect, this lets testing proceed smoothly in
builds that override DEFAULT_PGSOCKET_DIR.  Popular non-default values
like /var/run/postgresql are often unwritable to the build user.

Security: CVE-2014-0067
Revert "Secure Unix-domain sockets of "make check" temporary clusters."

About half of the buildfarm members use too-long directory names,
strongly suggesting that this approach is a dead end.
Fix typo in comment.

Amit Langote
Fix bugs in manipulation of PgBackendStatus.st_clienthostname.

Initialization of this field was not being done according to the
st_changecount protocol (it has to be done within the changecount increment
range, not outside).  And the test to see if the value should be reported
as null was wrong.  Noted while perusing uses of Port.remote_hostname.

This was wrong from the introduction of this code (commit 4a25bc145),
so back-patch to 9.1.
Fix assorted issues in client host name lookup.

The code for matching clients to pg_hba.conf lines that specify host names
(instead of IP address ranges) failed to complain if reverse DNS lookup
failed; instead it silently didn't match, so that you might end up getting
a surprising "no pg_hba.conf entry for ..." error, as seen in bug #9518
from Mike Blackwell.  Since we don't want to make this a fatal error in
situations where pg_hba.conf contains a mixture of host names and IP
addresses (clients matching one of the numeric entries should not have to
have rDNS data), remember the lookup failure and mention it as DETAIL if
we get to "no pg_hba.conf entry".  Apply the same approach to forward-DNS
lookup failures, too, rather than treating them as immediate hard errors.

Along the way, fix a couple of bugs that prevented us from detecting an
rDNS lookup error reliably, and make sure that we make only one rDNS lookup
attempt; formerly, if the lookup attempt failed, the code would try again
for each host name entry in pg_hba.conf.  Since more or less the whole
point of this design is to ensure there's only one lookup attempt not one
per entry, the latter point represents a performance bug that seems
sufficient justification for back-patching.

Also, adjust src/port/getaddrinfo.c so that it plays as well as it can
with this code.  Which is not all that well, since it does not have actual
support for rDNS lookup, but at least it should return the expected (and
required by spec) error codes so that the main code correctly perceives the
lack of functionality as a lookup failure.  It's unlikely that PG is still
being used in production on any machines that require our getaddrinfo.c,
so I'm not excited about working harder than this.

To keep the code in the various branches similar, this includes
back-patching commits c424d0d1052cb4053c8712ac44123f9b9a9aa3f2 and
1997f34db4687e671690ed054c8f30bb501b1168 into 9.2 and earlier.

Back-patch to 9.1 where the facility for hostnames in pg_hba.conf was
introduced.
Avoid palloc in critical section in GiST WAL-logging.

Memory allocation can fail if you run out of memory, and inside a critical
section that will lead to a PANIC. Use conservatively-sized arrays in stack
instead.

There was previously no explicit limit on the number of pages a GiST split
can produce, it was only limited by the number of LWLocks that can be held
simultaneously (100 at the moment). This patch adds an explicit limit of 75
pages. That should be plenty, a typical split shouldn't produce more than
2-3 page halves.

The bug has been there forever, but only backpatch down to 9.1. The code
was changed significantly in 9.1, and it doesn't seem worth the risk or
trouble to adapt this for 9.0 and 8.4.
Fix documentation about size of interval type.

It's been 16 bytes, not 12, for ages.  This was fixed in passing in HEAD
(commit 146604ec), but as a factual error it should have been back-patched.
Per gripe from Tatsuhito Kasahara.
Fix documentation about joining pg_locks to other views.

The advice to join to pg_prepared_xacts via the transaction column was not
updated when the transaction column was replaced by virtualtransaction.
Since it's not quite obvious how to do that join, give an explicit example.
For consistency also give an example for the adjacent case of joining to
pg_stat_activity.  And link-ify the view references too, just because we
can.  Per bug #9840 from Alexey Bashtanov.

Michael Paquier and Tom Lane
Avoid allocations in critical sections.

If a palloc in a critical section fails, it becomes a PANIC.
Fix tablespace creation WAL replay to work on Windows.

The code segment that removes the old symlink (if present) wasn't clued
into the fact that on Windows, symlinks are junction points which have
to be removed with rmdir().

Backpatch to 9.0, where the failing code was introduced.

MauMau, reviewed by Muhammad Asif Naeem and Amit Kapila
Fix processing of PGC_BACKEND GUC parameters on Windows.

EXEC_BACKEND builds (i.e., Windows) failed to absorb values of PGC_BACKEND
parameters if they'd been changed post-startup via the config file.  This
for example prevented log_connections from working if it were turned on
post-startup.  The mechanism for handling this case has always been a bit
of a kluge, and it wasn't revisited when we implemented EXEC_BACKEND.
While in a normal forking environment new backends will inherit the
postmaster's value of such settings, EXEC_BACKEND backends have to read
the settings from the CONFIG_EXEC_PARAMS file, and they were mistakenly
rejecting them.  So this case has always been broken in the Windows port;
so back-patch to all supported branches.

Amit Kapila
Block signals earlier during postmaster startup.

Formerly, we set up the postmaster's signal handling only when we were
about to start launching subprocesses.  This is a bad idea though, as
it means that for example a SIGINT arriving before that will kill the
postmaster instantly, perhaps leaving lockfiles, socket files, shared
memory, etc laying about.  We'd rather that such a signal caused orderly
postmaster termination including releasing of those resources.  A simple
fix is to move the PostmasterMain stanza that initializes signal handling
to an earlier point, before we've created any such resources.  Then, an
early-arriving signal will be blocked until we're ready to deal with it
in the usual way.  (The only part that really needs to be moved up is
blocking of signals, but it seems best to keep the signal handler
installation calls together with that; for one thing this ensures the
kernel won't drop any signals we wished to get.  The handlers won't get
invoked in any case until we unblock signals in ServerLoop.)

Per a report from MauMau.  He proposed changing the way "pg_ctl stop"
works to deal with this, but that'd just be masking one symptom not
fixing the core issue.

It's been like this since forever, so back-patch to all supported branches.
Fix hot standby bug with GiST scans.

Don't reset the rightlink of a page when replaying a page update record.
This was a leftover from pre-hot standby days, when it was not possible to
have scans concurrent with WAL replay. Resetting the right-link was not
necessary back then either, but it was done for the sake of tidiness. But
with hot standby, it's wrong, because a concurrent scan might still need it.

Backpatch all versions with hot standby, 9.0 and above.
Several fixes to array handling in ecpg.

Patches by Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>

Conflicts:
	src/interfaces/ecpg/test/expected/preproc-outofscope.c
Use correctly-sized buffer when zero-filling a WAL file.

I mixed up BLCKSZ and XLOG_BLCKSZ when I changed the way the buffer is
allocated a couple of weeks ago. With the default settings, they are both
8k, but they can be changed at compile-time.