Hmm, I don't have FreeBSD... I wish I had some environment to reproduce it...

I can give you temporary shell access to a FreeBSD box .. could you send me 
your public key? => tobias dot oberstein at tavendo dot de
Alternatively, I can prepare a virtual appliance that you can import into 
VirtualBox and run on your desktop.

The same exact thing happens for me:

- FreeBSD 9.0-STABLE (AMD64)
- V8 3.12.10
- PostgreSQL 9.1, 9.2dev, and 9.2 release.
- gcc/g++ v4.2.1
- plv8js 2012-07-19 snapshot

I've ktraced the PostgreSQL child running the query to define the 'to_jsontext' 
function on the home page after plv8 is loaded, if that helps at all.

[deleted comment]

Even such a simple UDF fails in the FreeBSD box.

extern "C" {
#include "postgres.h"
#include "fmgr.h"

PG_MODULE_MAGIC;

PG_FUNCTION_INFO_V1(miniv8);
Datum miniv8(PG_FUNCTION_ARGS);
}

#include "v8.h"

using namespace v8;

Datum
miniv8(PG_FUNCTION_ARGS)
{
    {
        HandleScope scope;

        Handle<ObjectTemplate> obj = ObjectTemplate::New();
    }

    PG_RETURN_BOOL(true);
}

Still I don't understand what is happening.

Is this related...?

https://github.com/cowboyd/therubyracer/issues/145

Can you try adding -fPIC in SConstruct and rebuild libv8.so?

Ah, never mind.  It's already there.

Oh, ok.  You need to build postgresql with -pthread.  Try:
./configure --prefix=$HOME/local CFLAGS='-pthread'

Note: don't forget -O2 in CFLAGS for your production.

...and installcheck still fails.

Well, no.  I was just messing up the source.  It works fine with -pthread.

I'll try with PG build with above option.

FWIW: the FreeBSD port for V8 does this patching:

/usr/ports/lang/v8/files
webmqpgdev# cat patch-SConstruct
--- SConstruct.orig     2012-02-08 09:38:50.000000000 +0800
+++ SConstruct  2012-02-08 09:50:13.000000000 +0800
@@ -115,7 +115,7 @@ LIBRARY_FLAGS = {
       'CPPPATH' : [src_dir, '/usr/local/include'],
       'LIBPATH' : ['/usr/local/lib'],
       'CCFLAGS':      ['-ansi'],
-      'LIBS': ['execinfo']
+      'LIBS': ['pthread', 'execinfo']
     },
     'os:openbsd': {
       'CPPPATH' : [src_dir, '/usr/local/include'],
webmqpgdev# cat patch-gyp_common.py
--- build/gyp/pylib/gyp/common.py.orig  2012-05-14 16:25:53.000000000 +0800
+++ build/gyp/pylib/gyp/common.py       2012-05-14 16:26:03.000000000 +0800
@@ -355,6 +355,8 @@ def GetFlavor(params):
     'sunos5': 'solaris',
     'freebsd7': 'freebsd',
     'freebsd8': 'freebsd',
+    'freebsd9': 'freebsd',
+    'freebsd10': 'freebsd',
   }
   flavor = flavors.get(sys.platform, 'linux')
   return params.get('flavor', flavor)
webmqpgdev#

Cool! I'll try in a moment. On success, I document the steps for building on 
FBSD in detail .. maybe that would be worth a page on the PLV8 wiki?

To be honest, PLV8 wiki page's V8 install instruction is out of date at all.  
I'll work on that soon.

Ok, confirmed that adding "-pthread" during PG build did the trick! Works for 
me now .. thanks alot for helping!

Build PostgreSQL
================

cd ~/build
tar xvjf ../tarballs/postgresql-9.2.0.tar.bz2
cd postgresql-9.2.0
./configure --prefix=$HOME/local CFLAGS='-O2 -pthread'
gmake
gmake install


Build Google V8
===============

cd ~/build
svn checkout http://v8.googlecode.com/svn/trunk/ v8
cd v8
export GYPFLAGS="-D OS=freebsd"
gmake dependencies
gmake native.check -j 4 library=shared strictaliasing=off console=readline
cp ./include/* ~/local/include/
cp ./out/native/lib.target/libv8.so ~/local/lib/
cp ./out/native/d8 ~/local/bin/


Build PLV8
==========

cd ~/build
git clone https://code.google.com/p/plv8js/
cd plv8js

Edit `Makefile` for

    V8DIR = ${HOME}/local

gmake
gmake install


Test PLV8
=========

To test, open a first shell and do

initdb -D $HOME/pgdata
postgres -D $HOME/pgdata
..

and in a 2nd shell do:

gmake installcheck

If you run PG on non-standard port (or have multiple PGs running),
adjust the Makefile, i.e.

REGRESS = --port 5433 --host 127.0.0.1 init-extension plv8 inline json 
startup_pre startup varparam

Updated a little of Wiki.