diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index 1649b105aa..d5fdd2ff9e 100644
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -1,5 +1,5 @@
 # Macros to detect C compiler features
-# $Header: /cvsroot/pgsql/config/c-compiler.m4,v 1.9 2003/10/25 15:32:11 petere Exp $
+# $Header: /cvsroot/pgsql/config/c-compiler.m4,v 1.10 2003/11/01 20:48:51 petere Exp $
 
 
 # PGAC_C_SIGNED
@@ -149,3 +149,43 @@ CFLAGS=$pgac_save_CFLAGS
 if test "$ac_env_CFLAGS_set" != set; then
   CFLAGS="$CFLAGS $pgac_cv_prog_cc_no_strict_aliasing"
 fi])# PGAC_PROG_CC_NO_STRICT_ALIASING
+
+
+# The below backpatches the following Autoconf change:
+#
+# 2002-03-28  Kevin Ryde  <user42@zip.com.au>
+#
+#         * lib/autoconf/c.m4 (AC_C_INLINE): Test with a typedef return value,
+#         to avoid versions of HP C which don't allow that.
+#
+# When we upgrade to Autoconf >= 2.53a then we can drop this and rely
+# on the standard macro.
+
+# AC_C_INLINE
+# -----------
+# Do nothing if the compiler accepts the inline keyword.
+# Otherwise define inline to __inline__ or __inline if one of those work,
+# otherwise define inline to be empty.
+AC_DEFUN([AC_C_INLINE],
+[AC_REQUIRE([AC_PROG_CC_STDC])dnl
+AC_CACHE_CHECK([for inline], ac_cv_c_inline,
+[ac_cv_c_inline=no
+for ac_kw in inline __inline__ __inline; do
+  AC_COMPILE_IFELSE([AC_LANG_SOURCE(
+[#ifndef __cplusplus
+typedef int foo_t;
+static $ac_kw foo_t static_foo () {return 0; }
+$ac_kw int foo () {return 0; }
+#endif
+])],
+                    [ac_cv_c_inline=$ac_kw; break])
+done
+])
+case $ac_cv_c_inline in
+  inline | yes) ;;
+  no) AC_DEFINE(inline,,
+                [Define as `__inline' if that's what the C compiler calls it,
+                 or to nothing if it is not supported.]) ;;
+  *)  AC_DEFINE_UNQUOTED(inline, $ac_cv_c_inline) ;;
+esac
+])# AC_C_INLINE
diff --git a/configure b/configure
index 992e289fbe..e7f93a27cc 100755
--- a/configure
+++ b/configure
@@ -2384,7 +2384,7 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
-pgac_CFLAGS_before_template=$CFLAGS
+unset CFLAGS
 
 #
 # Read the template
@@ -2399,12 +2399,15 @@ pgac_CFLAGS_before_template=$CFLAGS
 
 if test "$ac_env_CFLAGS_set" = set; then
   CFLAGS=$ac_env_CFLAGS_value
-elif test "$pgac_CFLAGS_before_template" != "$CFLAGS"; then
+elif test "${CFLAGS+set}" = set; then
   : # (keep what template set)
 elif test "$GCC" = yes; then
   CFLAGS="-O2"
 else
-  CFLAGS="-O"
+  # if the user selected debug mode, don't use -O
+  if test "$enable_debug" != yes; then
+    CFLAGS="-O"
+  fi
 fi
 
 # Need to specify -fno-strict-aliasing too in case it's gcc 3.3 or later.
@@ -2473,7 +2476,7 @@ if test "$ac_env_CFLAGS_set" != set; then
 fi
 
 # supply -g if --enable-debug
-if test "$enable_debug" = yes -a "$ac_cv_prog_cc_g" = yes; then
+if test "$enable_debug" = yes && test "$ac_cv_prog_cc_g" = yes; then
   CFLAGS="$CFLAGS -g"
 fi
 
@@ -9314,7 +9317,8 @@ for ac_kw in inline __inline__ __inline; do
 #line $LINENO "configure"
 #include "confdefs.h"
 #ifndef __cplusplus
-static $ac_kw int static_foo () {return 0; }
+typedef int foo_t;
+static $ac_kw foo_t static_foo () {return 0; }
 $ac_kw int foo () {return 0; }
 #endif
 
diff --git a/configure.in b/configure.in
index 46ee9d05c0..124be26ff0 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 1.299 2003/10/28 20:26:45 tgl Exp $
+dnl $Header: /cvsroot/pgsql/configure.in,v 1.300 2003/11/01 20:48:51 petere Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -229,7 +229,7 @@ esac
 
 AC_PROG_CC([$pgac_cc_list])
 
-pgac_CFLAGS_before_template=$CFLAGS
+unset CFLAGS
 
 #
 # Read the template
@@ -244,19 +244,22 @@ pgac_CFLAGS_before_template=$CFLAGS
 
 if test "$ac_env_CFLAGS_set" = set; then
   CFLAGS=$ac_env_CFLAGS_value
-elif test "$pgac_CFLAGS_before_template" != "$CFLAGS"; then
+elif test "${CFLAGS+set}" = set; then
   : # (keep what template set)
 elif test "$GCC" = yes; then
   CFLAGS="-O2"
 else
-  CFLAGS="-O"
+  # if the user selected debug mode, don't use -O
+  if test "$enable_debug" != yes; then
+    CFLAGS="-O"
+  fi
 fi
 
 # Need to specify -fno-strict-aliasing too in case it's gcc 3.3 or later.
 PGAC_PROG_CC_NO_STRICT_ALIASING
 
 # supply -g if --enable-debug
-if test "$enable_debug" = yes -a "$ac_cv_prog_cc_g" = yes; then
+if test "$enable_debug" = yes && test "$ac_cv_prog_cc_g" = yes; then
   CFLAGS="$CFLAGS -g"
 fi