Apparently, looking for an appropriately named file doesn't work on some
older versions, so put the back the explicit platform detection.

For building PL/Perl, PL/Python, and PL/Tcl, we need a shared library of
libperl, libpython, and libtcl, respectively.  Previously, this was
checked in the makefiles, skipping the PL build with a warning if no
shared library was available.  Now this is checked in configure, with an
error if no shared library is available.

The previous situation arose because in the olden days, the configure
options --with-perl, --with-python, and --with-tcl controlled whether
frontend interfaces for those languages would be built.  The procedural
languages were added later, and shared libraries were often not
available in the beginning.  So it was decided skip the builds of the
procedural languages in those cases.  The frontend interfaces have since
been removed from the tree, and shared libraries are now available most
of the time, so that setup makes much less sense now.

Also, the new setup allows contrib modules and pgxs users to rely on the
respective PLs being available based on configure flags.

On gcc and clang, the _mm_crc32_u8 and _mm_crc32_u64 intrinsics are not
defined at all, when not building with -msse4.2. But on icc, they are.
So we cannot assume that if those intrinsics are defined, we can always use
them safely, we might still need the runtime check.

To fix, check if the __SSE_4_2__ preprocessor symbol is defined. That's
supposed to be defined only when the compiler is targeting a processor that
has SSE 4.2 support.

Per buildfarm members fulmar and okapi.

Modern x86 and x86-64 processors with SSE 4.2 support have special
instructions, crc32b and crc32q, for calculating CRC-32C. They greatly
speed up CRC calculation.

Whether the instructions can be used or not depends on the compiler and the
target architecture. If generation of SSE 4.2 instructions is allowed for
the target (-msse4.2 flag on gcc and clang), use them. If they are not
allowed by default, but the compiler supports the -msse4.2 flag to enable
them, compile just the CRC-32C function with -msse4.2 flag, and check at
runtime whether the processor we're running on supports it. If it doesn't,
fall back to the slicing-by-8 algorithm. (With the common defaults on
current operating systems, the runtime-check variant is what you get in
practice.)

Abhijit Menon-Sen, heavily modified by me, reviewed by Andres Freund.

Considering the number of cases in which "unused" command line arguments
are silently ignored by compilers, it's fairly astonishing that anybody
thought this warning was useful; it's certainly nothing but an annoyance
when building Postgres.  One such case is that neither gcc nor clang
complain about unrecognized -Wno-foo switches, making it more difficult
to figure out whether the switch does anything than one could wish.

Back-patch to 9.3, which is as far back as the patch applies conveniently
(we'd have to back-patch PGAC_PROG_CC_VAR_OPT to go further, and it doesn't
seem worth that).

We will, for the foreseeable future, not expose 128 bit datatypes to
SQL. But being able to use 128bit math will allow us, in a later patch,
to use 128bit accumulators for some aggregates; leading to noticeable
speedups over using numeric.

So far we only detect a gcc/clang extension that supports 128bit math,
but no 128bit literals, and no *printf support. We might want to expand
this in the future to further compilers; if there are any that that
provide similar support.

Discussion: 544BB5F1.50709@proxel.se
Author: Andreas Karlsson, with significant editorializing by me
Reviewed-By: Peter Geoghegan, Oskari Saarenmaa

Oversight in my commit 91f4a5a9.
Per buildfarm member brolga.

Since commit ba7c5975, port/dirmod.c
has contained only Windows-specific functions.  Most platforms don't
seem to mind uselessly building an empty file, but OS X for one issues
warnings.  Hence, treat dirmod.c as a Windows-specific file selected
by configure rather than one that's always built.  We can revert this
change if dirmod.c ever gains any non-Windows functionality again.

Back-patch to 9.4 where the mentioned commit appeared.

This speeds up WAL generation and replay. The new algorithm is
significantly faster with large inputs, like full-page images or when
inserting wide rows. It is slower with tiny inputs, i.e. less than 10 bytes
or so, but the speedup with longer inputs more than make up for that. Even
small WAL records at least have 24 byte header in the front.

The output is identical to the current byte-at-a-time computation, so this
does not affect compatibility. The new algorithm is only used for the
CRC-32C variant, not the legacy version used in tsquery or the
"traditional" CRC-32 used in hstore and ltree. Those are not as performance
critical, and are usually only applied over small inputs, so it seems
better to not carry around the extra lookup tables to speed up those rare
cases.

Abhijit Menon-Sen

Previously, configure would add any switches that it chose of its own
accord to the end of the user-specified CFLAGS string.  Since most
compilers process these left-to-right, this meant that configure's choices
would override the user-specified flags in case of conflicts.  We'd rather
that worked the other way around, so adjust the logic to put the user's
string at the end not the beginning.

There does not seem to be a need for a similar behavior change for CPPFLAGS
or LDFLAGS: in those, the earlier switches tend to win (think -I or -L
behavior) so putting the user's string at the front is fine.

Backpatch to 9.4 but not earlier.  I'm not planning to run buildfarm member
guar on older branches, and it seems a bit risky to change this behavior
in long-stable branches.

We had code that supposed that some platforms might offer a nonstandard
version of getpwuid_r() with only four arguments.  However, the 5-argument
definition has been standardized at least since the Single Unix Spec v2,
which is our normal reference for what's portable across all Unix-oid
platforms.  (What's more, this wasn't the only pre-standardization version
of getpwuid_r(); my old HPUX 10.20 box has still another signature.)
So let's just get rid of the now-useless configure step.

Darwin --enable-nls builds use a substitute setlocale() that may start a
thread.  Buildfarm member orangutan experienced BackendList corruption
on account of different postmaster threads executing signal handlers
simultaneously.  Furthermore, a multithreaded postmaster risks undefined
behavior from sigprocmask() and fork().  Emit LOG messages about the
problem and its workaround.  Back-patch to 9.0 (all supported versions).

Backpatch certain files through 9.0

This eliminates gobs of "unrecognized format function type" warnings
under MinGW compilers predating GCC 4.4.

Don't skip the TAP tests anymore when IPC::Run is not found.  This will
fail normally now.

Discussion: 20140925133459.GB9633@alap3.anarazel.de
Author: Oskari Saarenmaa

Building the documentation with XSLT does not check the DTD, like a
DSSSL build would.  One can often get away with having invalid XML, but
the stylesheets might then create incorrect output, as they are not
designed to handle that.  Therefore, check the validity of the XML
against the DTD, using xmllint, during the build.

Add xmllint detection to configure, and add some documentation.

xmllint comes with libxml2, which is already in use, but it might be in
a separate package, such as libxml2-utils on Debian.

Reviewed-by: Fabien COELHO <coelho@cri.ensmp.fr>

Several upcoming performance/scalability improvements require atomic
operations. This new API avoids the need to splatter compiler and
architecture dependent code over all the locations employing atomic
ops.

For several of the potential usages it'd be problematic to maintain
both, a atomics using implementation and one using spinlocks or
similar. In all likelihood one of the implementations would not get
tested regularly under concurrency. To avoid that scenario the new API
provides a automatic fallback of atomic operations to spinlocks. All
properties of atomic operations are maintained. This fallback -
obviously - isn't as fast as just using atomic ops, but it's not bad
either. For one of the future users the atomics ontop spinlocks
implementation was actually slightly faster than the old purely
spinlock using implementation. That's important because it reduces the
fear of regressing older platforms when improving the scalability for
new ones.

The API, loosely modeled after the C11 atomics support, currently
provides 'atomic flags' and 32 bit unsigned integers. If the platform
efficiently supports atomic 64 bit unsigned integers those are also
provided.

To implement atomics support for a platform/architecture/compiler for
a type of atomics 32bit compare and exchange needs to be
implemented. If available and more efficient native support for flags,
32 bit atomic addition, and corresponding 64 bit operations may also
be provided. Additional useful atomic operations are implemented
generically ontop of these.

The implementation for various versions of gcc, msvc and sun studio have
been tested. Additional existing stub implementations for
* Intel icc
* HUPX acc
* IBM xlc
are included but have never been tested. These will likely require
fixes based on buildfarm and user feedback.

As atomic operations also require barriers for some operations the
existing barrier support has been moved into the atomics code.

Author: Andres Freund with contributions from Oskari Saarenmaa
Reviewed-By: Amit Kapila, Robert Haas, Heikki Linnakangas and Álvaro Herrera
Discussion: CA+TgmoYBW+ux5-8Ja=Mcyuy8=VXAnVRHp3Kess6Pn3DMXAPAEA@mail.gmail.com,
    20131015123303.GH5300@awork2.anarazel.de,
    20131028205522.GI20248@awork2.anarazel.de

Instead of just erroring out when a tool is missing, wrap the call with
the "missing" script that we are already using for bison, flex, and
perl, so that the users get a useful error message.

Commit a16bac36 let "configure" detect
the system getaddrinfo() when building under 64-bit MinGW-w64.  However,
src/include/port/win32/sys/socket.h assumes all native Windows
configurations use our replacement.  This change placates buildfarm
member jacana until we establish a plan for getaddrinfo() on Windows.

We have had INT64_FORMAT and UINT64_FORMAT for a long time, but that's not
good enough if you want something more exotic, like "%20lld".

Abhijit Menon-Sen, per Andres Freund's suggestion.

This refactoring is in preparation for adding support for other SSL
implementations, with no user-visible effects. There are now two #defines,
USE_OPENSSL which is defined when building with OpenSSL, and USE_SSL which
is defined when building with any SSL implementation. Currently, OpenSSL is
the only implementation so the two #defines go together, but USE_SSL is
supposed to be used for implementation-independent code.

The libpq SSL code is changed to use a custom BIO, which does all the raw
I/O, like we've been doing in the backend for a long time. That makes it
possible to use MSG_NOSIGNAL to block SIGPIPE when using SSL, which avoids
a couple of syscall for each send(). Probably doesn't make much performance
difference in practice - the SSL encryption is expensive enough to mask the
effect - but it was a natural result of this refactoring.

Based on a patch by Martijn van Oosterhout from 2006. Briefly reviewed by
Alvaro Herrera, Andreas Karlsson, Jeff Janes.

This restores the style of keeping configure.in free of AC_DEFUN.  Per
gripe from Tom Lane.

With OpenLDAP versions 2.4.24 through 2.4.31, inclusive, PostgreSQL
backends can crash at exit.  Raise a warning during "configure" based on
the compile-time OpenLDAP version number, and test the crash scenario in
the dblink test suite.  Back-patch to 9.0 (all supported versions).

Mingw uses a different header file than msvc, so we don't get the
hardcoded value, so we need the configure test to run.

Apparently we still build against OpenSSL so old that it doesn't
have this function, so add an autoconf check for it to make the
buildfarm happy. If the function doesn't exist, always return
that compression is disabled, since presumably the actual
compression functionality is always missing.

For now, hardcode the function as present on MSVC, since we should
hopefully be well beyond those old versions on that platform.

ws2_32 is the new version of the library that should be used, as
it contains the require functionality from wsock32 as well as some
more (which is why some binaries were already using ws2_32).

Michael Paquier, reviewed by MauMau

Almost ten years ago, commit e48322a6 broke
the logic in ACX_PTHREAD by looping through all the possible flags rather
than stopping with the first one that would work.  This meant that
$acx_pthread_ok was no longer meaningful after the loop; it would usually
be "no", whether or not we'd found working thread flags.  The reason nobody
noticed is that Postgres doesn't actually use any of the symbols set up
by the code after the loop.  Rather than complicate things some more to
make it work as designed, let's just remove all that dead code, and thereby
save a few cycles in each configure run.

Support for running postgres on Alpha hasn't been tested for a long
while. Due to Alpha's uniquely lax cache coherency model it's a hard
to develop for platform (especially blindly!) and thought to be
unlikely to currently work correctly.

As Alpha is the only supported architecture for Tru64 drop support for
it as well. Tru64's support has ended 2012 and it has been in
maintenance-only mode for much longer.

Also remove stray references to __ksr__ and ultrix defines.

This function is pervasive on free software operating systems; import
NetBSD's implementation.  Back-patch to 8.4, like the commit that will
harness it.

Let the hacking begin ...

Allow the contrib/uuid-ossp extension to be built atop any one of these
three popular UUID libraries.  (The extension's name is now arguably a
misnomer, but we'll keep it the same so as not to cause unnecessary
compatibility issues for users.)

We would not normally consider a change like this post-beta1, but the issue
has been forced by our upgrade to autoconf 2.69, whose more rigorous header
checks are causing OSSP's header files to be rejected on some platforms.
It's been foreseen for some time that we'd have to move away from depending
on OSSP UUID due to lack of upstream maintenance, so this is a down payment
on that problem.

While at it, add some simple regression tests, in hopes of catching any
major incompatibilities between the three implementations.

Matteo Beccati, with some further hacking by me

It's easy to forget using SYSTEMQUOTEs when constructing command strings
for system() or popen(). Even if we fix all the places missing it now, it is
bound to be forgotten again in the future. Introduce wrapper functions that
do the the extra quoting for you, and get rid of SYSTEMQUOTEs in all the
callers.

We previosly used SYSTEMQUOTEs in all the hard-coded command strings, and
this doesn't change the behavior of those. But user-supplied commands, like
archive_command, restore_command, COPY TO/FROM PROGRAM calls, as well as
pgbench's \shell, will now gain an extra pair of quotes. That is desirable,
but if you have existing scripts or config files that include an extra
pair of quotes, those might need to be adjusted.

Reviewed by Amit Kapila and Tom Lane

Reviewed-by: Pavel Stěhule <pavel.stehule@gmail.com>
Reviewed-by: Erik Rijkers <er@xs4all.nl>

The comment added by ed011d97 used #,
which means it gets copied into configure, but it doesn't make sense
there.  So use dnl, which gets dropped when creating configure.

Since C99, it's been standard for printf and friends to accept a "z" size
modifier, meaning "whatever size size_t has".  Up to now we've generally
dealt with printing size_t values by explicitly casting them to unsigned
long and using the "l" modifier; but this is really the wrong thing on
platforms where pointers are wider than longs (such as Win64).  So let's
start using "z" instead.  To ensure we can do that on all platforms, teach
src/port/snprintf.c to understand "z", and add a configure test to force
use of that implementation when the platform's version doesn't handle "z".

Having done that, modify a bunch of places that were using the
unsigned-long hack to use "z" instead.  This patch doesn't pretend to have
gotten everyplace that could benefit, but it catches many of them.  I made
an effort in particular to ensure that all uses of the same error message
text were updated together, so as not to increase the number of
translatable strings.

It's possible that this change will result in format-string warnings from
pre-C99 compilers.  We might have to reconsider if there are any popular
compilers that will warn about this; but let's start by seeing what the
buildfarm thinks.

Andres Freund, with a little additional work by me

krb5 has been deprecated since 8.3, and the recommended way to do
Kerberos authentication is using the GSSAPI authentication method
(which is still fully supported).

libpq retains the ability to identify krb5 authentication, but only
gives an error message about it being unsupported. Since all authentication
is initiated from the backend, there is no need to keep it at all
in the backend.

Update all files in head, and files COPYRIGHT and legal.sgml in all back
branches.