diff --git a/configure.ac b/configure.ac
index 5fa46b5..26c5abc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,424 +1,439 @@
 # configure.ac                                          -*- Autoconf -*-
 # Copyright (C) 2011, 2012 g10 Code GmbH
 #
 # This file is part of nPth.
 #
 # nPth is free software; you can redistribute it and/or modify it
 # under the terms of the GNU Lesser General Public License as
 # published by the Free Software Foundation; either version 2.1 of the
 # License, or (at your option) any later version.
 #
 # nPth is distributed in the hope that it will be useful, but WITHOUT
 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 # or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General
 # Public License for more details.
 #
 # You should have received a copy of the GNU Lesser General Public
 # License along with this program; if not, see <http://www.gnu.org/licenses/>.
 
 # Process this file with autoconf to produce a configure script.
 
 AC_PREREQ([2.67])
 min_automake_version="1.14"
 
 # To build a release you need to create a tag with the version number
 # (git tag -s npth-n.m) and run "./autogen.sh --force".  Please bump
 # the version number immediately after the release and do another
 # commit and push so that the git magic is able to work.
 # See below for the LT versions.
 m4_define([mym4_package],[npth])
 m4_define([mym4_major], [1])
 m4_define([mym4_minor], [7])
 
 # To start a new development series, i.e a new major or minor number
 # you need to mark an arbitrary commit before the first beta release
 # with an annotated tag.  For example a 2.1 branch starts off with
 # the tag "foo-2.1-base".  This is used as the base for counting
 # beta numbers before the first release of a series.
 
 # Below is m4 magic to extract and compute the git revision number,
 # the decimalized short revision number, a beta version string and a
 # flag indicating a development version (mym4_isbeta).  Note that the
 # m4 processing is done by autoconf and not during the configure run.
 m4_define([mym4_verslist], m4_split(m4_esyscmd([./autogen.sh --find-version] \
                            mym4_package mym4_major mym4_minor),[:]))
 m4_define([mym4_isbeta],       m4_argn(2, mym4_verslist))
 m4_define([mym4_version],      m4_argn(4, mym4_verslist))
 m4_define([mym4_revision],     m4_argn(7, mym4_verslist))
 m4_define([mym4_revision_dec], m4_argn(8, mym4_verslist))
 m4_esyscmd([echo ]mym4_version[>VERSION])
 AC_INIT([mym4_package],[mym4_version],[https://bugs.gnupg.org])
 # LT Version numbers, remember to change them just *before* a release.
 #   (Code changed:			REVISION++)
 #   (Interfaces added/removed/changed:	CURRENT++, REVISION=0)
 #   (Interfaces added:			AGE++)
 #   (Interfaces removed:		AGE=0)
 #
 LIBNPTH_LT_CURRENT=1
 LIBNPTH_LT_AGE=1
 LIBNPTH_LT_REVISION=2
 ################################################
 
 AC_SUBST(LIBNPTH_LT_CURRENT)
 AC_SUBST(LIBNPTH_LT_AGE)
 AC_SUBST(LIBNPTH_LT_REVISION)
 
 VERSION_NUMBER=m4_esyscmd(printf "0x%02x%02x00" mym4_major mym4_minor)
 AC_SUBST(VERSION_NUMBER)
 
 # If the API is changed in an incompatible way: increment the next counter.
 NPTH_CONFIG_API_VERSION=1
 ##############################################
 
 AC_CONFIG_AUX_DIR([build-aux])
 AM_INIT_AUTOMAKE([serial-tests dist-bzip2 no-dist-gzip])
 AM_MAINTAINER_MODE
 AC_CONFIG_SRCDIR([src/npth.c])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_MACRO_DIR([m4])
 AC_CANONICAL_HOST
 AM_SILENT_RULES
 
 # Enable GNU extensions on systems that have them.
 AC_USE_SYSTEM_EXTENSIONS
 
 # Taken from mpfr-4.0.1, then modified for LDADD_FOR_TESTS_KLUDGE
 dnl Under Linux, make sure that the old dtags are used if LD_LIBRARY_PATH
 dnl is defined. The issue is that with the new dtags, LD_LIBRARY_PATH has
 dnl the precedence over the run path, so that if a compatible MPFR library
 dnl is installed in some directory from $LD_LIBRARY_PATH, then the tested
 dnl MPFR library will be this library instead of the MPFR library from the
 dnl build tree. Other OS with the same issue might be added later.
 dnl
 dnl References:
 dnl   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=859732
 dnl   http://lists.gnu.org/archive/html/libtool/2017-05/msg00000.html
 dnl
 dnl We need to check whether --disable-new-dtags is supported as alternate
 dnl linkers may be used (e.g., with tcc: CC=tcc LD=tcc).
 dnl
 case $host in
   *-*-linux*)
     if test -n "$LD_LIBRARY_PATH"; then
       saved_LDFLAGS="$LDFLAGS"
       LDADD_FOR_TESTS_KLUDGE="-Wl,--disable-new-dtags"
       LDFLAGS="$LDFLAGS $LDADD_FOR_TESTS_KLUDGE"
       AC_MSG_CHECKING(whether --disable-new-dtags is supported by the linker)
       AC_LINK_IFELSE([AC_LANG_SOURCE([[
 int main (void) { return 0; }
       ]])],
       [AC_MSG_RESULT(yes (use it since LD_LIBRARY_PATH is set))],
       [AC_MSG_RESULT(no)
        LDADD_FOR_TESTS_KLUDGE=""
       ])
       LDFLAGS="$saved_LDFLAGS"
     fi
     ;;
 esac
 AC_SUBST([LDADD_FOR_TESTS_KLUDGE])
 
 AH_VERBATIM([_REENTRANT],
 [#ifndef _REENTRANT
 # define _REENTRANT 1
 #endif])
 
 # Checks for programs.
 AC_PROG_CC
 
+if test "$GCC" = yes; then
+    CFLAGS="$CFLAGS -Wall -Wcast-align -Wshadow -Wstrict-prototypes"
+
+    AC_MSG_CHECKING([if gcc supports -Wpointer-arith])
+    _gcc_cflags_save=$CFLAGS
+    CFLAGS="-Wpointer-arith"
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],_gcc_wopt=yes,_gcc_wopt=no)
+    AC_MSG_RESULT($_gcc_wopt)
+    CFLAGS=$_gcc_cflags_save;
+    if test x"$_gcc_wopt" = xyes ; then
+       CFLAGS="$CFLAGS -Wpointer-arith"
+    fi
+fi
+
+
 run_tests="yes"
 AC_ARG_ENABLE(tests,
   AS_HELP_STRING([--disable-tests],[disable tests]),
          run_tests=$enableval)
 AM_CONDITIONAL(RUN_TESTS, test "$run_tests" = "yes")
 
 
 # Don't default to build static libs.
 LT_PREREQ([2.2.6])
 LT_INIT([win32-dll disable-static])
 LT_LANG([Windows Resource])
 
 
 # For now we hardcode the use of version scripts.  It would be better
 # to write a test for this or even implement this within libtool.
 have_ld_version_script=no
 case "${host}" in
     *-*-linux*)
         have_ld_version_script=yes
         ;;
     *-*-gnu*)
         have_ld_version_script=yes
         ;;
     *-apple-darwin*)
         AC_SEARCH_LIBS([dispatch_semaphore_create],[dispatch],
         [AC_DEFINE([HAVE_LIB_DISPATCH],1,[Defined if we have libdispatch])])
         ;;
     *-*-aix*)
         have_fork_unsafe_semaphore=yes
         ;;
     *-*-dragonfly*|*-*-freebsd*|*-*-netbsd*|*-*-hpux*)
         LIBS="-lpthread $LIBS"
         AC_SEARCH_LIBS([sem_init],[rt])
         ;;
 esac
 
 AM_CONDITIONAL(HAVE_LD_VERSION_SCRIPT, test "$have_ld_version_script" = "yes")
 if test "$have_fork_unsafe_semaphore" = yes; then
    AC_DEFINE(HAVE_FORK_UNSAFE_SEMAPHORE, 1, [Defined if we have fork-unsafe semaphore])
 fi
 
 # Set some default values
 config_libs="-lnpth $LIBS"
 have_w32_system=no
 have_w32ce_system=no
 have_w64_system=no
 
 # Define OS macros
 case "${host}" in
     x86_64-*mingw32*)
         have_w64_system=yes
         ;;
     *-mingw32ce*)
         have_w32ce_system=yes
         ;;
 esac
 case "${host}" in
     *-mingw32ce*|*-mingw32*)
         have_w32_system=yes
         ;;
     *)
         ;;
 esac
 
 if test "$have_w32_system" = yes; then
    AC_DEFINE(HAVE_W32_SYSTEM,1,
              [Defined if we run on any kind of W32 API based system])
 fi
 AM_CONDITIONAL(HAVE_W32_SYSTEM, test "$have_w32_system" = yes)
 
 if test "$have_w64_system" = yes; then
    AC_DEFINE(HAVE_W64_SYSTEM,1,
              [Defined if we run on a 64 bit W32 API based system])
 fi
 AM_CONDITIONAL(HAVE_W64_SYSTEM, test "$have_w64_system" = yes)
 
 #
 # Generate values for the DLL version info
 #
 if test "$have_w32_system" = yes; then
     BUILD_ISODATE=`date --iso-8601`
     changequote(,)dnl
     BUILD_FILEVERSION=`echo "$VERSION" | sed 's/\([0-9.]*\).*/\1./;s/\./,/g'`
     changequote([,])dnl
     BUILD_FILEVERSION="${BUILD_FILEVERSION}git_revision_dec"
 fi
 AC_SUBST(BUILD_ISODATE)
 AC_SUBST(BUILD_FILEVERSION)
 AC_ARG_ENABLE([build-timestamp],
   AS_HELP_STRING([--enable-build-timestamp],[set an explicit build timestamp for reproducibility.
                   (default is the current time in ISO-8601 format)]),
      [if test "$enableval" = "yes"; then
         BUILD_TIMESTAMP=`date -u +%Y-%m-%dT%H:%M+0000 2>/dev/null || date`
       else
         BUILD_TIMESTAMP="$enableval"
       fi],
      [BUILD_TIMESTAMP="<none>"])
 AC_SUBST(BUILD_TIMESTAMP)
 AC_DEFINE_UNQUOTED(BUILD_TIMESTAMP, "$BUILD_TIMESTAMP",
                    [The time this package was configured for a build])
 
 
 #
 # Checks for header files.
 #
 # fixme: For what do we need the sys/socket test?
 AC_CHECK_HEADERS([sys/socket.h sys/select.h unistd.h sys/time.h time.h \
                   signal.h])
 INSERT_SYS_SELECT_H=
 if test x"$ac_cv_header_sys_select_h" = xyes; then
   INSERT_SYS_SELECT_H="include <sys/select.h>"
 fi
 AC_SUBST(INSERT_SYS_SELECT_H)
 
 if test x"$ac_cv_header_sys_time_h" = xyes; then
   INSERT_SYS_TIME_H="include <sys/time.h>"
 fi
 AC_SUBST(INSERT_SYS_TIME_H)
 
 if test x"$ac_cv_header_time_h" = xyes; then
   INSERT_TIME_H="include <time.h>"
 fi
 AC_SUBST(INSERT_TIME_H)
 
 if test x"$ac_cv_header_signal_h" = xyes; then
   INSERT_SIGNAL_H="include <signal.h>"
 fi
 AC_SUBST(INSERT_SIGNAL_H)
 
 
 # Some systems lack socklen_t - provide a replacement.
 gl_TYPE_SOCKLEN_T
 case "${host}" in
   *-*-mingw32*)
     # socklen_t may or may not be defined depending on what headers
     # are included.  To be safe we use int as this is the actual type.
     INSERT_SOCKLEN_T="define _npth_socklen_t int"
     ;;
   *)
     if test ".$gl_cv_socklen_t_equiv" = "."; then
       INSERT_SOCKLEN_T="define _npth_socklen_t socklen_t"
     else
       INSERT_SOCKLEN_T="define _npth_socklen_t ${gl_cv_socklen_t_equiv}"
     fi
 esac
 AC_SUBST(INSERT_SOCKLEN_T)
 
 
 #
 # Checks for typedefs, structures, and compiler characteristics.
 #
 AC_TYPE_PID_T
 AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T
 
 
 #
 # Checks for libraries and functions.
 #
 #   We test for pthread_cancel because in glibc 2.34, libc includes
 #   pthread_create and pthread_detach, but not pthread_cancel.
 if test "$have_w32_system" = no; then
   AC_SEARCH_LIBS([pthread_cancel],[pthread])
   case "x$ac_cv_search_pthread_cancel" in
     xno)
       have_pthread=no
       ;;
     xnone\ required)
       have_pthread=yes
       ;;
     *)
       have_pthread=yes
       config_libs="$config_libs $ac_cv_search_pthread_cancel"
       ;;
   esac
   if test "$have_pthread" != no; then
     AC_DEFINE(HAVE_PTHREAD,1,[Define if we have pthread.])
     AC_CHECK_TYPE([pthread_rwlock_t])
     AC_CHECK_FUNCS([pthread_tryjoin_np pthread_setname_np pthread_getname_np])
     AC_CHECK_FUNCS([pthread_mutex_timedlock])
     AC_CHECK_FUNCS([pthread_rwlock_rdlock pthread_rwlock_wrlock])
     AC_CHECK_FUNCS([pthread_rwlock_timedrdlock pthread_rwlock_timedwrlock])
     AC_CHECK_FUNCS([pthread_rwlock_tryrdlock pthread_rwlock_trywrlock])
     AC_CHECK_FUNCS([pthread_atfork])
   fi
 fi
 
 INSERT_NO_RWLOCK="undef _NPTH_NO_RWLOCK"
 if test x"$ac_cv_type_pthread_rwlock_t" = xno; then
   INSERT_NO_RWLOCK="define _NPTH_NO_RWLOCK 1"
 fi
 AC_SUBST(INSERT_NO_RWLOCK)
 
 case "${host}" in
     *-*-linux*|*-*-gnu*)
         INSERT_EXPOSE_RWLOCK_API="defined(__USE_UNIX98) || defined(__USE_XOPEN2K)"
         ;;
     *)
         INSERT_EXPOSE_RWLOCK_API="1"
         ;;
 esac
 AC_SUBST(INSERT_EXPOSE_RWLOCK_API)
 
 AC_CHECK_FUNCS([select pselect gettimeofday])
 
 npth_LIBSOCKET
 config_libs="$config_libs $LIBSOCKET"
 
 # Save and restore LIBS so e.g., -lrt, isn't added to it.  Otherwise, *all*
 # programs in the package would end up linked with that potentially-shared
 # library, inducing unnecessary run-time overhead.
 LIB_CLOCK_GETTIME=
 AC_SUBST([LIB_CLOCK_GETTIME])
 gl_saved_libs=$LIBS
 AC_SEARCH_LIBS([clock_gettime], [rt posix4],
                [if test "$ac_cv_search_clock_gettime" != "none required"; then
                   LIB_CLOCK_GETTIME=$ac_cv_search_clock_gettime
                   config_libs="$config_libs $LIB_CLOCK_GETTIME"
                 fi
                 AC_DEFINE([HAVE_CLOCK_GETTIME],1,
                   [Define to 1 if you have the `clock_gettime' function.])
                 ])
 LIBS=$gl_saved_libs
 
 
 #
 # Set NETLIBS
 #
 if test "$have_w32ce_system" = yes; then
    NETLIBS="-lws2 $NETLIBS"
 elif test "$have_w32_system" = yes; then
    NETLIBS="-lws2_32 $NETLIBS"
 fi
 AC_SUBST(NETLIBS)
 
 
 #
 # Substitutions to set generated files in a Emacs buffer to read-only.
 #
 AC_SUBST(emacs_local_vars_begin, [['Local][ ][Variables:']])
 AC_SUBST(emacs_local_vars_read_only, ['buffer-read-only: t'])
 AC_SUBST(emacs_local_vars_end, ['End:'])
 
 
 #
 # Substitution used for npth-config
 #
 NPTH_CONFIG_LIBS="$config_libs"
 NPTH_CONFIG_CFLAGS=""
 NPTH_CONFIG_HOST="$host"
 AC_SUBST(NPTH_CONFIG_API_VERSION)
 AC_SUBST(NPTH_CONFIG_LIBS)
 AC_SUBST(NPTH_CONFIG_CFLAGS)
 AC_SUBST(NPTH_CONFIG_HOST)
 
 #
 # Last check.
 #
 die=no
 if test "$have_w32_system" = no; then
   if test "$have_pthread" = "no"; then
      die=yes
      AC_MSG_NOTICE([[
 ***
 *** You need Pthread to build this program.
 *** Normally, this library comes with your system.  On Windows, you can use:
 ***   http://sourceware.org/pthreads-win32/
 ***]])
   fi
 fi
 
 if test "$die" = "yes"; then
     AC_MSG_ERROR([[
 ***
 *** Required libraries not found. Please consult the above messages
 *** and install them before running configure again.
 ***]])
 fi
 
 #
 # Write output
 #
 AC_CONFIG_FILES([Makefile
 npth.pc
 src/npth.h
 src/Makefile
 w32/Makefile
 tests/Makefile])
 AC_CONFIG_FILES(npth-config, chmod +x npth-config)
 AC_OUTPUT
 
 echo "
         $PACKAGE_NAME v$PACKAGE_VERSION prepared for make
 
         Revision: mym4_revision  (mym4_revision_dec)
         Platform: $host
 "