diff --git a/acinclude.m4 b/acinclude.m4
index dc6d0f4..2d13d20 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -1,24 +1,78 @@
-# Custom m4 macros for Open Source Tripwire 2.4.3
-# a non-symlinky variant of AC_PROG_LN_S, via: http://www.opensource.apple.com/source/zsh/zsh-34/zsh/aclocal.m4
-#
-AC_DEFUN([AC_PROG_LN],
-[AC_MSG_CHECKING(whether ln works)
-AC_CACHE_VAL(ac_cv_prog_LN,
-[rm -f conftestdata conftestlink
-echo > conftestdata
-if ln conftestdata conftestlink 2>/dev/null
-then
-  rm -f conftestdata conftestlink
-  ac_cv_prog_LN="ln"
-else
-  rm -f conftestdata
-  ac_cv_prog_LN="cp"
-fi])dnl
-LN="$ac_cv_prog_LN"
-if test "$ac_cv_prog_LN" = "ln"; then
-  AC_MSG_RESULT(yes)
-else
-  AC_MSG_RESULT(no)
-fi
-AC_SUBST(LN)dnl
-])
\ No newline at end of file
+# Custom m4 macros for Open Source Tripwire 2.4.3
+
+# a non-symlinky variant of AC_PROG_LN_S, via: http://www.opensource.apple.com/source/zsh/zsh-34/zsh/aclocal.m4
+#
+AC_DEFUN([AC_PROG_LN],
+[AC_MSG_CHECKING(whether ln works)
+AC_CACHE_VAL(ac_cv_prog_LN,
+[rm -f conftestdata conftestlink
+echo > conftestdata
+if ln conftestdata conftestlink 2>/dev/null
+then
+  rm -f conftestdata conftestlink
+  ac_cv_prog_LN="ln"
+else
+  rm -f conftestdata
+  ac_cv_prog_LN="cp"
+fi])dnl
+LN="$ac_cv_prog_LN"
+if test "$ac_cv_prog_LN" = "ln"; then
+  AC_MSG_RESULT(yes)
+else
+  AC_MSG_RESULT(no)
+fi
+AC_SUBST(LN)dnl
+])
+
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the current language's compiler
+#   or gives an error.  (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the current language's default
+#   flags (e.g. CFLAGS) when the check is done.  The check is thus made with
+#   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
+#   force the compiler to issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+AC_DEFUN([AX_CHECK_COMPILE_FLAG],
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+  ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
+  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
+AS_VAR_IF(CACHEVAR,yes,
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_COMPILE_FLAGS
+
diff --git a/configure.ac b/configure.ac
index 83e05b2..d276c25 100644
--- a/configure.ac
+++ b/configure.ac
@@ -11,13 +11,14 @@ AM_CONFIG_HEADER(config.h)
 AC_COPYRIGHT([The developer of the original code and/or files is Tripwire, Inc.  Portions created by Tripwire, Inc. are copyright 2000-2019 Tripwire, Inc.  Tripwire is a registered trademark of Tripwire, Inc.  All rights reserved.])
 AC_REVISION([$Revision: 2.4.3.8 $])
 
+AC_LANG_CPLUSPLUS
 
 
 dnl ###################
 dnl Checks for programs
 dnl ###################
-AC_PROG_CC([gcc clang suncc aCC gxlc xlC_r xlC cl.exe])
-AC_PROG_CXX([g++ c++ clang++ sunCC aCC gxlc++ xlC_r xlC cl.exe])
+AC_PROG_CC([gcc clang suncc aCC xlc_r gxlc xlC_r xlC cl.exe])
+AC_PROG_CXX([g++ c++ clang++ sunCC aCC xlc++_r gxlc++ xlC_r xlC cl.exe])
 AC_PROG_RANLIB
 AC_PROG_YACC
 AC_PROG_LN_S
@@ -29,44 +30,66 @@ AC_PROG_AR
 AC_PATH_PROG(path_to_vi, vi)
 AC_PATH_PROG(path_to_sendmail, sendmail, "", [$PATH:/usr/libexec])
 
+
+dnl #########################################
+dnl Set up per-compiler constants & base args
+dnl #########################################
+
 if test "x${GXX}" != "x"; then
- AC_DEFINE(HAVE_GCC, 1, [Uses the GNU gcc compiler])
+    AC_DEFINE(HAVE_GCC, 1, [Uses the GNU gcc compiler])
+
+    CFLAGS=${CFLAGS:-"-O -pipe -Wall"}
+    CXXFLAGS=${CXXFLAGS:-"-O -pipe -Wall"}
 else
- AC_DEFINE(HAVE_GCC, 0, [Uses the GNU gcc compiler])
+    AC_DEFINE(HAVE_GCC, 0, [Uses the GNU gcc compiler])
 fi
 
 if test "x${CXX}" = "xclang++"; then
- AC_DEFINE(HAVE_CLANG, 1, [Uses the Clang compiler])
+    AC_DEFINE(HAVE_CLANG, 1, [Uses the Clang compiler])
+
+    CFLAGS=${CFLAGS:-"-O -pipe -Wall"}
+    CXXFLAGS=${CXXFLAGS:-"-O -pipe -Wall"}
 else
- AC_DEFINE(HAVE_CLANG, 0, [Uses the Clang compiler])
+    AC_DEFINE(HAVE_CLANG, 0, [Uses the Clang compiler])
 fi
 
-if test "x${CXX}" = "xgxlc++"; then
- AC_DEFINE(HAVE_IBM_GXLC, 1, [Uses the gxlc++ compiler])
+if test "x${CXX}" = "xxlc++_r"; then
+    AC_DEFINE(HAVE_CLANG, 1, [Uses the IBM XL C++ compiler])
+
+    CFLAGS=${CFLAGS:-"-O -maix64 -Wx,-qinfo=all" }
+    CXXFLAGS=${CXXFLAGS:-"-O -maix64 -Wx,-qinfo=all"}
 else
- AC_DEFINE(HAVE_IBM_GXLC, 0, [Uses the gxlc++ compiler])
+    AC_DEFINE(HAVE_CLANG, 0, [Uses the IBM XL C++ compiler])
+fi
+
+
+dnl *** TODO these compilers need work on default args ****
+
+if test "x${CXX}" = "xgxlc++"; then
+    AC_DEFINE(HAVE_IBM_GXLC, 1, [Uses the gxlc++ compiler])
+else
+    AC_DEFINE(HAVE_IBM_GXLC, 0, [Uses the gxlc++ compiler])
 fi
 
 if test "x${CXX}" = "xsunCC"; then
- AC_DEFINE(HAVE_ORACLE_SUNCC, 1, [Uses the sunCC compiler])
+    AC_DEFINE(HAVE_ORACLE_SUNCC, 1, [Uses the sunCC compiler])
 else
- AC_DEFINE(HAVE_ORACLE_SUNCC, 0, [Uses the sunCC compiler])
+    AC_DEFINE(HAVE_ORACLE_SUNCC, 0, [Uses the sunCC compiler])
 fi
 
 if test "x${CXX}" = "xaCC"; then
- AC_DEFINE(HAVE_HP_ACC, 1, [Uses the aCC compiler])
+    AC_DEFINE(HAVE_HP_ACC, 1, [Uses the aCC compiler])
 else
- AC_DEFINE(HAVE_HP_ACC, 0, [Uses the aCC compiler])
+    AC_DEFINE(HAVE_HP_ACC, 0, [Uses the aCC compiler])
 fi
 
-
-dnl #####################
-dnl Set up base compiler flags
+dnl ######################
+dnl Enable various warnings
 dnl #####################
 
-CFLAGS=${CFLAGS:-"-O -pipe -Wall -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64"}
-CXXFLAGS=${CXXFLAGS:-"-O -pipe -Wall -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64"}
-
+AX_CHECK_COMPILE_FLAG([-Wall],        [CXXFLAGS="$CXXFLAGS -Wall"])
+AX_CHECK_COMPILE_FLAG([-Wextra],      [CXXFLAGS="$CXXFLAGS -Wextra -Wno-unused-parameter"])
+dnl AX_CHECK_COMPILE_FLAG([-Weverything], [CXXFLAGS="$CXXFLAGS -Weverything"])
 
 dnl #####################
 dnl Configuration options
@@ -117,6 +140,23 @@ then
    AC_DEFINE(ENABLE_DEV_URANDOM, 1, [Enable use of /dev/urandom])
 fi
 
+AC_ARG_WITH(stlport-dir,
+    [  --with-stlport-dir=PATH     Specify path to STLport installation ],
+    [
+        if test "x$withval" != "xno" ; then
+            stlport_base    = $withval
+            stlport_include = "${stlport_base}/stlport"
+            stlport_lib     = "${stlport_base}/lib"
+            stlport_paths   = "-I ${stlport_include} -L ${stlport_lib}"
+
+            CPPFLAGS = "${CPPFLAGS} ${stlport_paths}"
+            CFLAGS="${CFLAGS} ${stlport_paths}"
+            CXXFLAGS="${CXXFLAGS} ${stlport_paths}"
+            LDFLAGS="${LDFLAGS} ${stlport_lib} -lstlport_gcc"
+        fi
+    ]
+)
+
 
 dnl #######################
 dnl Checks for header files
@@ -158,6 +198,7 @@ dnl All platforms we support use 2's complement, are byte aligned, etc...
 AC_DEFINE(USES_1S_COMPLEMENT, 0, [Uses one's complement])
 AC_DEFINE(USES_2S_COMPLEMENT, 1, [Uses two's complement])
 AC_DEFINE(USES_SIGNED_MAGNITUDE, 0, [Uses signed magnitute])
+
 AC_DEFINE(IS_BYTE_ALIGNED, 1, [Is byte aligned])
 AC_DEFINE(EXCEPTION_NAMESPACE, std::, [this is the prefix for STL exception functions])
 
@@ -167,11 +208,14 @@ dnl target is unix.  This can still be changed in config.h
 AC_DEFINE(IS_UNIX, 1, [Is a unix type platform])
 
 dnl whether or not to generate debuging code?
-AC_DEFINE(NDEBUG, 1, [don't generate debuging code])
+dnl this gets defined elsewhere based on config args AC_DEFINE(NDEBUG, 1, [don't generate debuging code])
 
 dnl look for struct stat members that aren't always there
 AC_CHECK_MEMBERS([struct stat.st_rdev, struct stat.st_blocks])
 
+dnl detect large file support & use it where available
+AC_SYS_LARGEFILE
+
 dnl #############################
 dnl Checks for standard functions
 dnl #############################
@@ -197,6 +241,10 @@ AC_CHECK_HEADERS(door.h, [AC_CHECK_FUNCS(door_create)])
 dnl check for event port support (Solaris)
 AC_CHECK_HEADERS(port.h, [AC_CHECK_FUNCS(port_create)])
 
+dnl check for existence of fseeko() as well as ftello()
+AC_FUNC_FSEEKO
+
+
 dnl ##############################################  
 dnl check for various RNG/PRNG devices
 dnl ##############################################  
@@ -391,7 +439,7 @@ case $target in
 		 then
 		 AC_MSG_WARN( [
 
-Sorry, tripwire will not properly link staticaly under Solaris.
+Sorry, tripwire will not properly link statically under Solaris.
 This is due to tripwire's extensive use of gethostbyname(),
 which can only be linked dynamicaly.  Please rerun configure
 without the --enable-static option.