diff --git a/configure b/configure
index 3dd2f4dccc..55530ade97 100755
--- a/configure
+++ b/configure
@@ -2824,7 +2824,11 @@ if test "${with_threads+set}" = set; then
 
   case $withval in
     yes)
-      :
+
+cat >>confdefs.h <<\_ACEOF
+#define USE_THREADS 1
+_ACEOF
+
       ;;
     no)
       :
@@ -2841,6 +2845,7 @@ else
 
 fi;
 
+
 echo "$as_me:$LINENO: result: $with_threads" >&5
 echo "${ECHO_T}$with_threads" >&6
 
@@ -3899,9 +3904,12 @@ case $host_os in
 			# these require no special flags or libraries
 			;;
 		freebsd2*|freebsd3*|freebsd4*) THREAD_CFLAGS="-pthread" ;;
-		freebsd*) THREAD_LIBS="-lc_r" ;;
-		linux*) THREAD_LIBS="-lpthread"
-			THREAD_CFLAGS="-D_REENTRANT" ;;
+		freebsd*)
+			THREAD_LIBS="-lc_r"
+			;;
+		linux*) THREAD_CFLAGS="-D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS"
+			THREAD_LIBS="-lpthread"
+			;;
 		*)
 			# other operating systems might fail because they have pthread.h but need
 			# special libs we don't know about yet.
@@ -3918,7 +3926,7 @@ so it can be added to the next release.  Report any compile or link flags,
 or libraries required for threading support.
 " >&2;}
    { (exit 1); exit 1; }; }
-	esac
+esac
 fi
 
 
@@ -12818,6 +12826,97 @@ _ACEOF
 fi
 
 
+#
+# Check for re-entrant versions of certain functions
+#
+# Include special flags if required
+#
+_CFLAGS="$CFLAGS"
+_LIB="$LIBS"
+CFLAGS="$CFLAGS $TREAD_CFLAGS"
+LIBS="$LIBS $THREAD_LIBS"
+
+
+
+for ac_func in strerror_r getpwuid_r gethostbyname_r
+do
+as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
+echo "$as_me:$LINENO: checking for $ac_func" >&5
+echo $ECHO_N "checking for $ac_func... $ECHO_C" >&6
+if eval "test \"\${$as_ac_var+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+#line $LINENO "configure"
+#include "confdefs.h"
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $ac_func (); below.  */
+#include <assert.h>
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char $ac_func ();
+char (*f) ();
+
+#ifdef F77_DUMMY_MAIN
+#  ifdef __cplusplus
+     extern "C"
+#  endif
+   int F77_DUMMY_MAIN() { return 1; }
+#endif
+int
+main ()
+{
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
+choke me
+#else
+f = $ac_func;
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+         { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  eval "$as_ac_var=yes"
+else
+  echo "$as_me: failed program was:" >&5
+cat conftest.$ac_ext >&5
+eval "$as_ac_var=no"
+fi
+rm -f conftest.$ac_objext conftest$ac_exeext conftest.$ac_ext
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_var'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_var'}'`" >&6
+if test `eval echo '${'$as_ac_var'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
+CFLAGS="$_CFLAGS"
+LIB="$_LIBS"
+
+
 
 # This test makes sure that run tests work at all.  Sometimes a shared
 # library is found by the linker, but the runtime linker can't find it.
@@ -17603,8 +17702,8 @@ s,@with_pam@,$with_pam,;t t
 s,@with_rendezvous@,$with_rendezvous,;t t
 s,@with_openssl@,$with_openssl,;t t
 s,@ELF_SYS@,$ELF_SYS,;t t
-s,@THREAD_LIBS@,$THREAD_LIBS,;t t
 s,@THREAD_CFLAGS@,$THREAD_CFLAGS,;t t
+s,@THREAD_LIBS@,$THREAD_LIBS,;t t
 s,@AWK@,$AWK,;t t
 s,@FLEX@,$FLEX,;t t
 s,@FLEXFLAGS@,$FLEXFLAGS,;t t
diff --git a/configure.in b/configure.in
index f323dc767f..b8c533d05d 100644
--- a/configure.in
+++ b/configure.in
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $Header: /cvsroot/pgsql/configure.in,v 1.261 2003/06/13 23:10:07 momjian Exp $
+dnl $Header: /cvsroot/pgsql/configure.in,v 1.262 2003/06/14 14:35:42 momjian Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -323,7 +323,9 @@ IFS=$ac_save_IFS
 # Enable libpq to be thread-safe
 #
 AC_MSG_CHECKING([allow threaded libpq])
-PGAC_ARG_BOOL(with, threads, no, [  --with-threads          allow libpq to be thread-safe])
+PGAC_ARG_BOOL(with, threads, no, [  --with-threads          allow libpq to be thread-safe],
+              [AC_DEFINE([USE_THREADS], 1, [Define to 1 to build libpq with threads. (--with-threads)])])
+
 AC_MSG_RESULT([$with_threads])
 AC_SUBST(with_threads)
 
@@ -559,9 +561,12 @@ case $host_os in
 			# these require no special flags or libraries
 			;;
 		freebsd2*|freebsd3*|freebsd4*) THREAD_CFLAGS="-pthread" ;;
-		freebsd*) THREAD_LIBS="-lc_r" ;;
-		linux*) THREAD_LIBS="-lpthread"
-			THREAD_CFLAGS="-D_REENTRANT" ;;
+		freebsd*)
+			THREAD_LIBS="-lc_r"
+			;;
+		linux*) THREAD_CFLAGS="-D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS"
+			THREAD_LIBS="-lpthread"
+			;;
 		*)
 			# other operating systems might fail because they have pthread.h but need
 			# special libs we don't know about yet.
@@ -571,10 +576,10 @@ Please report your platform threading info to the PostgreSQL mailing lists
 so it can be added to the next release.  Report any compile or link flags,
 or libraries required for threading support.
 ])
-	esac
+esac
 fi
-AC_SUBST(THREAD_LIBS)
 AC_SUBST(THREAD_CFLAGS)
+AC_SUBST(THREAD_LIBS)
 
 #
 # Assignments
@@ -983,6 +988,20 @@ AC_CHECK_FUNCS(atexit, [],
 
 AC_FUNC_FSEEKO
 
+#
+# Check for re-entrant versions of certain functions
+#
+# Include special flags if required
+#
+_CFLAGS="$CFLAGS"
+_LIB="$LIBS"
+CFLAGS="$CFLAGS $TREAD_CFLAGS"
+LIBS="$LIBS $THREAD_LIBS"
+AC_CHECK_FUNCS([strerror_r getpwuid_r gethostbyname_r])
+CFLAGS="$_CFLAGS"
+LIB="$_LIBS"
+
+
 
 # This test makes sure that run tests work at all.  Sometimes a shared
 # library is found by the linker, but the runtime linker can't find it.
diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index b08830bb9f..c1087b743c 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -1,5 +1,5 @@
 # -*-makefile-*-
-# $Header: /cvsroot/pgsql/src/Makefile.global.in,v 1.163 2003/05/27 16:36:50 momjian Exp $
+# $Header: /cvsroot/pgsql/src/Makefile.global.in,v 1.164 2003/06/14 14:35:42 momjian Exp $
 
 #------------------------------------------------------------------------------
 # All PostgreSQL makefiles include this file and use the variables it sets,
@@ -121,6 +121,7 @@ localedir := @localedir@
 #
 # Records the choice of the various --enable-xxx and --with-xxx options.
 
+with_threads	= @with_threads@
 with_java	= @with_java@
 with_perl	= @with_perl@
 with_python	= @with_python@
@@ -340,7 +341,7 @@ endif
 #
 # substitute implementations of the C library
 
-LIBOBJS = @LIBOBJS@ path.o
+LIBOBJS = @LIBOBJS@ path.o threads.o
 
 ifneq (,$(LIBOBJS))
 LIBS += -lpgport
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 60f9536dff..6e8cac0e99 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -121,6 +121,9 @@
 /* Define to 1 if you have the `getaddrinfo' function. */
 #undef HAVE_GETADDRINFO
 
+/* Define to 1 if you have the `gethostbyname_r' function. */
+#undef HAVE_GETHOSTBYNAME_R
+
 /* Define to 1 if you have the `gethostname' function. */
 #undef HAVE_GETHOSTNAME
 
@@ -136,6 +139,9 @@
 /* Define to 1 if you have the `getpeereid' function. */
 #undef HAVE_GETPEEREID
 
+/* Define to 1 if you have the `getpwuid_r' function. */
+#undef HAVE_GETPWUID_R
+
 /* Define to 1 if you have the `getrusage' function. */
 #undef HAVE_GETRUSAGE
 
@@ -375,6 +381,9 @@
 /* Define to 1 if you have the `strerror' function. */
 #undef HAVE_STRERROR
 
+/* Define to 1 if you have the `strerror_r' function. */
+#undef HAVE_STRERROR_R
+
 /* Define to 1 if cpp supports the ANSI # stringizing operator. */
 #undef HAVE_STRINGIZE
 
@@ -579,6 +588,9 @@
 /* Define to select SysV-style shared memory. */
 #undef USE_SYSV_SHARED_MEMORY
 
+/* Define to 1 to build libpq with threads. (--with-threads) */
+#undef USE_THREADS
+
 /* Define to select unnamed POSIX semaphores. */
 #undef USE_UNNAMED_POSIX_SEMAPHORES
 
diff --git a/src/include/port.h b/src/include/port.h
index 783d41cc0e..16f733d67c 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -6,11 +6,15 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: port.h,v 1.6 2003/06/12 08:15:29 momjian Exp $
+ * $Id: port.h,v 1.7 2003/06/14 14:35:42 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
 
+/* for thread.c */
+#include <pwd.h>
+#include <netdb.h>
+
 /* Portable path handling for Unix/Win32 */
 bool is_absolute_path(const char *filename);
 char *first_path_separator(const char *filename);
@@ -98,3 +102,15 @@ extern long random(void);
 #ifndef HAVE_SRANDOM
 extern void srandom(unsigned int seed);
 #endif
+
+/* thread.h */
+extern char *pqStrerror(int errnum, char *strerrbuf, size_t buflen);
+
+extern int pqGetpwuid(uid_t uid, struct passwd *resultbuf, char *buffer,
+		      size_t buflen, struct passwd **result);
+
+extern int pqGethostbyname(const char *name,
+			   struct hostent *resbuf,
+			   char *buf, size_t buflen,
+			   struct hostent **result,
+			   int *herrno);
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b6a5ec8f75..2a178b8e9d 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -4,7 +4,7 @@
 #
 # Copyright (c) 1994, Regents of the University of California
 #
-# $Header: /cvsroot/pgsql/src/interfaces/libpq/Makefile,v 1.81 2003/06/12 17:31:50 momjian Exp $
+# $Header: /cvsroot/pgsql/src/interfaces/libpq/Makefile,v 1.82 2003/06/14 14:35:42 momjian Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -23,7 +23,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS) $(THREAD_CFLAGS) -DFRONTEND -DSYSCO
 OBJS= fe-auth.o fe-connect.o fe-exec.o fe-misc.o fe-print.o fe-lobj.o \
       fe-protocol2.o fe-protocol3.o pqexpbuffer.o pqsignal.o fe-secure.o \
       dllist.o md5.o ip.o wchar.o encnames.o \
-      $(filter crypt.o getaddrinfo.o inet_aton.o snprintf.o strerror.o path.o, $(LIBOBJS))
+      $(filter crypt.o getaddrinfo.o inet_aton.o snprintf.o strerror.o path.o threads.o, $(LIBOBJS))
 
 
 # Add libraries that libpq depends (or might depend) on into the
@@ -46,9 +46,13 @@ backend_src = $(top_srcdir)/src/backend
 # For port modules, this only happens if configure decides the module
 # is needed (see filter hack in OBJS, above).
 
-crypt.c getaddrinfo.c inet_aton.c snprintf.c strerror.c path.c: %.c : $(top_srcdir)/src/port/%.c
+crypt.c getaddrinfo.c inet_aton.c snprintf.c strerror.c path.c threads.c: %.c : $(top_srcdir)/src/port/%.c
 	rm -f $@ && $(LN_S) $< .
 
+# compile this with thread flags
+thread.o: thread.c
+	$(CC) $(CFLAGS) $(THREAD_CFLAGS) -c thread.c
+
 dllist.c: $(backend_src)/lib/dllist.c
 	rm -f $@ && $(LN_S) $< .
 
diff --git a/src/port/Makefile b/src/port/Makefile
index 04d9e04994..d6de2d8890 100644
--- a/src/port/Makefile
+++ b/src/port/Makefile
@@ -7,7 +7,7 @@
 # with broken/missing library files.
 
 # IDENTIFICATION
-#    $Header: /cvsroot/pgsql/src/port/Makefile,v 1.3 2002/07/27 20:10:05 petere Exp $
+#    $Header: /cvsroot/pgsql/src/port/Makefile,v 1.4 2003/06/14 14:35:42 momjian Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -22,5 +22,8 @@ endif
 libpgport.a: $(LIBOBJS)
 	$(AR) crs $@ $^
 
+thread.o: thread.c
+	$(CC) $(CFLAGS) $(THREAD_CFLAGS) -c thread.c
+
 clean distclean maintainer-clean:
 	rm -f libpgport.a $(LIBOBJS)
diff --git a/src/port/threads.c b/src/port/threads.c
new file mode 100644
index 0000000000..5012cac281
--- /dev/null
+++ b/src/port/threads.c
@@ -0,0 +1,85 @@
+/*-------------------------------------------------------------------------
+ *
+ * threads.c
+ *
+ *		  Prototypes and macros around system calls, used to help make
+ *		  threaded libraries reentrant and safe to use from threaded applications.
+ *
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ *
+ * $Id: threads.c,v 1.1 2003/06/14 14:35:42 momjian Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+/*
+ * Wrapper around strerror and strerror_r to use the former if it is
+ * available and also return a more useful value (the error string).
+ */
+char *
+pqStrerror(int errnum, char *strerrbuf, size_t buflen)
+{
+#if defined(USE_THREADS) && defined(HAVE_STRERROR_R)
+	/* reentrant strerror_r is available */
+	/* some early standards had strerror_r returning char * */
+	strerror_r(errnum, strerrbuf, buflen);
+	return (strerrbuf);
+#else
+	/* no strerror_r() available, just use strerror */
+	return strerror(errnum);
+#endif
+}
+
+/*
+ * Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
+ * behaviour, if it is not available.
+ */
+int
+pqGetpwuid(uid_t uid, struct passwd * resultbuf, char *buffer,
+		   size_t buflen, struct passwd ** result)
+{
+#if defined(USE_THREADS) && defined(HAVE_GETPWUID_R)
+	/*
+	 * broken (well early POSIX draft) getpwuid_r() which returns 'struct
+	 * passwd *'
+	 */
+	*result = getpwuid_r(uid, resultbuf, buffer, buflen);
+#else
+	/* no getpwuid_r() available, just use getpwuid() */
+	*result = getpwuid(uid);
+#endif
+	return (*result == NULL) ? -1 : 0;
+}
+
+/*
+ * Wrapper around gethostbyname() or gethostbyname_r() to mimic
+ * POSIX gethostbyname_r() behaviour, if it is not available.
+ */
+int
+pqGethostbyname(const char *name,
+				struct hostent * resbuf,
+				char *buf, size_t buflen,
+				struct hostent ** result,
+				int *herrno)
+{
+#if defined(USE_THREADS) && defined(HAVE_GETHOSTBYNAME_R)
+	/*
+	 * broken (well early POSIX draft) gethostbyname_r() which returns
+	 * 'struct hostent *'
+	 */
+	*result = gethostbyname_r(name, resbuf, buf, buflen, herrno);
+	return (*result == NULL) ? -1 : 0;
+#else
+	/* no gethostbyname_r(), just use gethostbyname() */
+	*result = gethostbyname(name);
+	if (*result != NULL)
+		return 0;
+	else
+	{
+		*herrno = h_errno;
+		return -1;
+	}
+#endif
+}