We had put a test for libxml2's xmlStructuredErrorContext variable in
configure, but of course that doesn't work on Windows builds.  The next
best alternative seems to be to test the LIBXML_VERSION symbol provided
by xmlversion.h.

Per report from Talha Bin Rizwan, though this fixes it in a different way
than his proposed patch.

ENABLE_DTRACE            unused as of a7b7b07a
HAVE_ERR_SET_MARK        unused as of 4ed4b6c5
HAVE_FCVT                unused as of 4553e1d8
HAVE_STRUCT_SOCKADDR_UN  unused as of b4cea00a
HAVE_SYSCONF             unused as of f83356c7
TM_IN_SYS_TIME           never used, obsolescent per Autoconf documentation

These should have been removed when the BeOS port was removed in
44f90212.

These were apparently never used.  The AC_SUBST was probably just
added in a copy-and-paste manner.  (The shell variables continue to be
used inside configure.  The change is just that we don't need them
outside of configure.)

These should not be needed anymore, at least after the recent port
removals.  So let's see whether we can do without them.

Postgres 9.2, and perhaps no existing users either.

Remove the following ports:

- dgux
- nextstep
- sunos4
- svr4
- ultrix4
- univel

These are obsolete and not worth rescuing.  In most cases, there is
circumstantial evidence that they wouldn't work anymore anyway.

In the Fedora variant of MinGW, the openssl libraries have their normal
names, not libeay32 and libssleay32.  Adjust configure probes to allow
that, per bug #6486.

Tomasz Ostrowski

The immediate impetus for this is that Noah Misch's patch to elide
unnecessary table and index rebuilds when changing typmod for temporal
types uses it; and this is extracted from that patch, with some
further commentary by me.  But it seems logically separate from the
remainder of the patch, so I'm committing it separately; this is not
the first time someone has wanted fls() in the backend and probably
won't be the last.

If we end up using this in more performance-critical spots it may be
worthwhile to add some architecture-specific optimizations to our
src/port version of fls() - e.g. any x86 platform can implement this
using the assembly instruction BSRL.  But performance won't matter
a bit for assessing typmod changes, so I'm not worried about that
right now.

Historically we've used the SWPB instruction for TAS() on ARM, but this
is deprecated and not available on ARMv6 and later.  Instead, make use
of a GCC builtin if available.  We'll still fall back to SWPB if not,
so as not to break existing ports using older GCC versions.

Eventually we might want to try using __sync_lock_test_and_set() on some
other architectures too, but for now that seems to present only risk and
not reward.

Back-patch to all supported versions, since people might want to use any
of them on more recent ARM chips.

Martin Pitt

The hint bit makes for a small but measurable performance improvement
in access to contended spinlocks.

On the other hand, some PPC chips give an illegal-instruction failure.
There doesn't seem to be a completely bulletproof way to tell whether the
hint bit will cause an illegal-instruction failure other than by trying
it; but most if not all 64-bit PPC machines should accept it, so follow
the Linux kernel's lead and assume it's okay to use it in 64-bit builds.
Of course we must also check whether the assembler accepts the command,
since even with a recent CPU the toolchain could be old.

Patch by Manabu Ori, significantly modified by me.

All supported platforms support the C89 standard function atexit()
(SunOS 4 probably being the last one not to), and supporting both
makes the code clumsy.

Suggested solution from Tom Lane. Problem discovered, probably not
for the first time, while testing the mingw-w64 32 bit compiler.

Backpatched to all live branches.

Original patch by Lars Kanis, reviewed by Nishiyama Tomoaki and tweaked some by me.

This compiler, or at least the latest version of it, is currently broken, and
only passes the regression tests if built with -O0.

--- we were not using the scandir pattern filtering anyway.  This also
removes the scandir requirement in configure.

Add __attribute__ decorations for printf format checking to the places that
were missing them.  Fix the resulting warnings.  Add
-Wmissing-format-attribute to the standard set of warnings for GCC, so these
don't happen again.

The warning fixes here are relatively harmless.  The one serious problem
discovered by this was already committed earlier in
cf15fb5c.

KaiGai Kohei

on Windows. ecpglib doesn't link with libpgport, but picks and compiles
the .c files it needs individually. To cope with that, move the setlocale()
wrapper from chklocale.c to a separate setlocale.c file, and include that
in ecpglib.

Without this, it's not very easy to tell which compiler version a buildfarm
animal is actually using at the moment.

glibc renders random() thread-safe by wrapping a futex lock around it;
testing reveals that this limits the performance of pgbench on machines
with many CPU cores.  Rather than switching to random_r(), which is
only available on GNU systems and crashes unless you use undocumented
alchemy to initialize the random state properly, switch to our built-in
implementation of erand48(), which is both thread-safe and concurrent.

Since the list of reasons not to use the operating system's erand48()
is getting rather long, rename ours to pg_erand48() (and similarly
for our implementations of lrand48() and srand48()) and just always
use those.  We were already doing this on Cygwin anyway, and the
glibc implementation is not quite thread-safe, so pgbench wouldn't
be able to use that either.

Per discussion with Tom Lane.

Windows doesn't have Unix sockets, so it's not needed, and moreover causes compile warnings.

libxml reports some errors (like invalid xmlns attributes) via the error
handler hook, but still returns a success indicator to the library caller.
This causes us to miss some errors that are important to report.  Since the
"generic" error handler hook doesn't know whether the message it's getting
is for an error, warning, or notice, stop using that and instead start
using the "structured" error handler hook, which gets enough information
to be useful.

While at it, arrange to save and restore the error handler hook setting in
each libxml-using function, rather than assuming we can set and forget the
hook.  This should improve the odds of working nicely with third-party
libraries that also use libxml.

In passing, volatile-ize some local variables that get modified within
PG_TRY blocks.  I noticed this while testing with an older gcc version
than I'd previously tried to compile xml.c with.

Florian Pflug and Tom Lane, with extensive review/testing by Noah Misch

Flexible array members are a C99 feature that avoids "cheating" in the
declaration of variable-length arrays at the end of structs.  With
Autoconf support, this should be transparent for older compilers.

We start with one use in gist.h because gcc 4.6 started to raise a
warning there.  Over time, it can be expanded to other places in the
source, but they will likely need some review of sizeof and offsetof
usage.  The current change in gist.h appears to be safe in this
regard.

This unifies a bunch of ugly #ifdef's in one place.  Per discussion,
we only need this where HAVE_UNIX_SOCKETS, so no need to cover Windows.

Marko Kreen, some adjustment by Tom Lane

It turns out the reason we hadn't found out about the portability issues
with our credential-control-message code is that almost no modern platforms
use that code at all; the ones that used to need it now offer getpeereid(),
which we choose first.  The last holdout was NetBSD, and they added
getpeereid() as of 5.0.  So far as I can tell, the only live platform on
which that code was being exercised was Debian/kFreeBSD, ie, FreeBSD kernel
with Linux userland --- since glibc doesn't provide getpeereid(), we fell
back to the control message code.  However, the FreeBSD kernel provides a
LOCAL_PEERCRED socket parameter that's functionally equivalent to Linux's
SO_PEERCRED.  That is both much simpler to use than control messages, and
superior because it doesn't require receiving a message from the other end
at just the right time.

Therefore, add code to use LOCAL_PEERCRED when necessary, and rip out all
the credential-control-message code in the backend.  (libpq still has such
code so that it can still talk to pre-9.1 servers ... but eventually we can
get rid of it there too.)  Clean up related autoconf probes, too.

This means that libpq's requirepeer parameter now works on exactly the same
platforms where the backend supports peer authentication, so adjust the
documentation accordingly.

This is reported to be necessary on some versions of that OS.  In service
of this, cause PGAC_PROG_CC_CFLAGS_OPT to reject switches that result in
compiler warnings, since on yet other versions of that OS, the switch does
nothing except provoke a warning.

Report and patch by Ibrar Ahmed, further tweaking by me.

We need at least version 2.0.93, so probe for a function that was added
in that version.

Kaigai Kohei

With some compilers such as Clang and ICC emulating GCC, using a
version string of the form "GCC $version" can be quite misleading.
Also, a great while ago, the version output from gcc --version started
including the string "gcc", so it is redundant to repeat that.  In
order to support ancient GCC versions, we now prefix the result with
"GCC " only if the version output does not start with a letter.

These functions should take a pg_locale_t, not a collation OID, and should
call mbstowcs_l/wcstombs_l where available.  Where those functions are not
available, temporarily select the correct locale with uselocale().

This change removes the bogus assumption that all locales selectable in
a given database have the same wide-character conversion method; in
particular, the collate.linux.utf8 regression test now passes with
LC_CTYPE=C, so long as the database encoding is UTF8.

I decided to move the char2wchar/wchar2char functions out of mbutils.c and
into pg_locale.c, because they work on wchar_t not pg_wchar_t and thus
don't really belong with the mbutils.c functions.  Keeping them where they
were would have required importing pg_locale_t into pg_wchar.h somehow,
which did not seem like a good plan.

Mapped to NetBSD, the closest existing match.  (Even though DragonFly
BSD is derived from FreeBSD, the shared library version numbering
matches NetBSD, and the rest is mostly the same among all BSD
variants.)

per "Rumko"