Optionally use xml2-config to detect installation locations of libxml.

configure

@@ -314,7 +314,7 @@ ac_includes_default="\
 # include <unistd.h>
 #endif"
 
-ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS configure_args build build_cpu build_vendor build_os host host_cpu host_vendor host_os PORTNAME docdir enable_nls WANTED_LANGUAGES default_port enable_shared enable_rpath enable_debug DTRACE DTRACEFLAGS enable_dtrace CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC EXEEXT OBJEXT CPP GCC TAS autodepend INCLUDES enable_thread_safety with_tcl with_perl with_python with_krb5 krb_srvtab with_pam with_ldap with_bonjour with_openssl with_zlib EGREP ELF_SYS LDFLAGS_SL AWK FLEX FLEXFLAGS LN_S LD with_gnu_ld ld_R_works RANLIB ac_ct_RANLIB TAR STRIP ac_ct_STRIP STRIP_STATIC_LIB STRIP_SHARED_LIB YACC YFLAGS PERL perl_archlibexp perl_privlibexp perl_useshrplib perl_embed_ldflags PYTHON python_version python_configdir python_includespec python_libdir python_libspec python_additional_libs HAVE_IPV6 LIBOBJS acx_pthread_config PTHREAD_CC PTHREAD_LIBS PTHREAD_CFLAGS LDAP_LIBS_FE LDAP_LIBS_BE HAVE_POSIX_SIGNALS MSGFMT MSGMERGE XGETTEXT localedir TCLSH TCL_CONFIG_SH TCL_INCLUDE_SPEC TCL_LIB_FILE TCL_LIBS TCL_LIB_SPEC TCL_SHARED_BUILD TCL_SHLIB_LD_LIBS NSGMLS JADE have_docbook DOCBOOKSTYLE COLLATEINDEX SGMLSPL vpath_build LTLIBOBJS'
+ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS configure_args build build_cpu build_vendor build_os host host_cpu host_vendor host_os PORTNAME docdir enable_nls WANTED_LANGUAGES default_port enable_shared enable_rpath enable_debug DTRACE DTRACEFLAGS enable_dtrace CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC EXEEXT OBJEXT CPP GCC TAS autodepend INCLUDES enable_thread_safety with_tcl with_perl with_python with_krb5 krb_srvtab with_pam with_ldap with_bonjour with_openssl XML2_CONFIG with_zlib EGREP ELF_SYS LDFLAGS_SL AWK FLEX FLEXFLAGS LN_S LD with_gnu_ld ld_R_works RANLIB ac_ct_RANLIB TAR STRIP ac_ct_STRIP STRIP_STATIC_LIB STRIP_SHARED_LIB YACC YFLAGS PERL perl_archlibexp perl_privlibexp perl_useshrplib perl_embed_ldflags PYTHON python_version python_configdir python_includespec python_libdir python_libspec python_additional_libs HAVE_IPV6 LIBOBJS acx_pthread_config PTHREAD_CC PTHREAD_LIBS PTHREAD_CFLAGS LDAP_LIBS_FE LDAP_LIBS_BE HAVE_POSIX_SIGNALS MSGFMT MSGMERGE XGETTEXT localedir TCLSH TCL_CONFIG_SH TCL_INCLUDE_SPEC TCL_LIB_FILE TCL_LIBS TCL_LIB_SPEC TCL_SHARED_BUILD TCL_SHLIB_LD_LIBS NSGMLS JADE have_docbook DOCBOOKSTYLE COLLATEINDEX SGMLSPL vpath_build LTLIBOBJS'
 ac_subst_files=''
 
 # Initialize some variables set by options.
@@ -4196,6 +4196,61 @@ else
 fi;
 
 
+if test "$with_libxml" = yes ; then
+  for ac_prog in xml2-config
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+echo "$as_me:$LINENO: checking for $ac_word" >&5
+echo $ECHO_N "checking for $ac_word... $ECHO_C" >&6
+if test "${ac_cv_prog_XML2_CONFIG+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  if test -n "$XML2_CONFIG"; then
+  ac_cv_prog_XML2_CONFIG="$XML2_CONFIG" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+  for ac_exec_ext in '' $ac_executable_extensions; do
+  if $as_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_XML2_CONFIG="$ac_prog"
+    echo "$as_me:$LINENO: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+done
+
+fi
+fi
+XML2_CONFIG=$ac_cv_prog_XML2_CONFIG
+if test -n "$XML2_CONFIG"; then
+  echo "$as_me:$LINENO: result: $XML2_CONFIG" >&5
+echo "${ECHO_T}$XML2_CONFIG" >&6
+else
+  echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6
+fi
+
+  test -n "$XML2_CONFIG" && break
+done
+
+  if test -n "$XML2_CONFIG"; then
+    for pgac_option in `$XML2_CONFIG --cflags`; do
+      case $pgac_option in
+        -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+      esac
+    done
+    for pgac_option in `$XML2_CONFIG --libs`; do
+      case $pgac_option in
+        -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+      esac
+    done
+  fi
+fi
+
 
 #
 # Zlib
@@ -23794,6 +23849,7 @@ s,@with_pam@,$with_pam,;t t
 s,@with_ldap@,$with_ldap,;t t
 s,@with_bonjour@,$with_bonjour,;t t
 s,@with_openssl@,$with_openssl,;t t
+s,@XML2_CONFIG@,$XML2_CONFIG,;t t
 s,@with_zlib@,$with_zlib,;t t
 s,@EGREP@,$EGREP,;t t
 s,@ELF_SYS@,$ELF_SYS,;t t

configure.in

 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.496 2007/01/07 21:10:40 petere Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.497 2007/01/18 14:07:31 petere Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -537,6 +537,22 @@ PGAC_ARG_BOOL(with, libedit-preferred, no,
 PGAC_ARG_BOOL(with, libxml, no, [  --with-libxml           build with XML support],
               [AC_DEFINE([USE_LIBXML], 1, [Define to 1 to build with XML support. (--with-libxml)])])
 
+if test "$with_libxml" = yes ; then
+  AC_CHECK_PROGS(XML2_CONFIG, xml2-config)
+  if test -n "$XML2_CONFIG"; then
+    for pgac_option in `$XML2_CONFIG --cflags`; do
+      case $pgac_option in
+        -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+      esac
+    done
+    for pgac_option in `$XML2_CONFIG --libs`; do
+      case $pgac_option in
+        -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+      esac
+    done
+  fi
+fi
+
 
 #
 # Zlib

doc/src/sgml/installation.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.271 2007/01/07 21:10:41 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.272 2007/01/18 14:07:31 petere Exp $ -->
 
 <chapter id="installation">
  <title><![%standalone-include[<productname>PostgreSQL</>]]>
@@ -912,6 +912,18 @@ su - postgres
          Build with libxml (enables SQL/XML support).  Libxml version 2.6.23 or
          later is required for this feature.
         </para>
+
+        <para>
+         Libxml installs a program <command>xml2-config</command> that
+         can be used to detect the required compiler and linker
+         options.  PostgreSQL will use it automatically if found.  To
+         specify a libxml installation at an unusual location, you can
+         either set the environment variable
+         <envar>XML2_CONFIG</envar> to point to the
+         <command>xml2-config</command> program belonging to the
+         installation, or use the options
+         <option>--with-includes</option> and
+         <option>--with-libraries</option>.
        </listitem>
       </varlistentry>
 
@@ -1202,6 +1214,16 @@ su - postgres
        </listitem>
       </varlistentry>
 
+      <varlistentry>
+       <term><envar>XML2_CONFIG</envar></term>
+       <listitem>
+        <para>
+         <command>xml2-config</command> program used to locate the
+         libxml installation.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry>
        <term><envar>YACC</envar></term>
        <listitem>