# configure.ac for the libcoap package
#
# Copyright (C) 2010-2024 Olaf Bergmann <bergmann@tzi.org>
# Copyright (C) 2015-2018 Carsten Schoenert <c.schoenert@t-online.de>
# Copyright (C) 2018-2024 Jon Shallow <supjps-libcoap@jpshallow.com>
#
# SPDX-License-Identifier: BSD-2-Clause
#
# This file is part of the CoAP library libcoap. Please see README for terms
# of use.
#
# Please run 'autogen.sh' to let autoconf produce a configure script.

# Define the libcoap software version here. Note! The libtool versions are
# defined later.
m4_define([libcoap_major_version], [4])
m4_define([libcoap_minor_version], [3])
m4_define([libcoap_micro_version], [5])

# define an appending release state if needed, for example for pre-releases
# like 'alpha' or 'rc1', for a full release keep the value empty!
m4_define([libcoap_release_state], [])

# Define the previous full libcoap software release version here.
# Used if libcoap_release_state is not empty for LIBCOAP_VERSION and LIBCOAP_PACKAGE_BASE.
# Set to libcoap software version when libcoap_release_state is reset to empty.
m4_define([libcoap_pre_major_version], [4])
m4_define([libcoap_pre_minor_version], [3])
m4_define([libcoap_pre_micro_version], [4])

# concatenate the full libcoap version string
m4_define([libcoap_version], [m4_format([%s.%s.%s%s], libcoap_major_version, libcoap_minor_version, libcoap_micro_version, libcoap_release_state)])

AC_INIT([libcoap], [libcoap_version], [libcoap-developers@lists.sourceforge.net], [libcoap], [https://libcoap.net/])
AC_PREREQ([2.64])
AM_INIT_AUTOMAKE([1.10 -Wall no-define no-dist-gzip dist-bzip2])
PKG_PROG_PKG_CONFIG([0.20])
AM_SILENT_RULES([yes])
AC_HEADER_ASSERT

# Generate one configuration header file for building the library itself with
# an auto generated template. We need later a second one
# (include/coap$LIBCOAP_API_VERSION/libcoap.h) that will be installed alongside the library.
AC_CONFIG_HEADERS([coap_config.h])

AC_PROG_CC
AM_PROG_CC_C_O
AC_PROG_SED
AC_CONFIG_MACRO_DIR([m4])
m4_pattern_allow([AM_PROG_AR])
AM_PROG_AR
AC_PROG_LN_S
AC_PROG_MKDIR_P

AC_C_BIGENDIAN

# enable the automatically build of shared and static libraries
LT_INIT([shared static])

# Setting the libtool versioning
###################################################################################
#                                                                                 #
#  To set the version of the library, libtool provides the -version-info          #
#  parameter, which accepts three numbers, separated by colons, that are called   #
#  respectively, current, revision and age. Both their name and their behavior,   #
#  nowadays, have to be considered fully arbitrary, as the explanation provided   #
#  in the official documentation is confusing to say the least, and can be, in    #
#  some cases, considered completely wrong.                                       #
#  https://autotools.io/libtool/version.html                                      #
#                                                                                 #
###################################################################################
#
# How to work with the libtool versioning?
#
# Follow the following steps from top to bottom. This means always start at point 1
# if you plan to make a release and change the values.
# Every new library starts with a version 'current'  (short 'c') = 0
#                                         'revision' (short 'r') = 0
#                                         'age'      (short 'a') = 0
#
# Update the libtool versioning only just before the release of a public release of libcoap.
# Go through the following checklist from top to bottom and check your needs, following
# the reminded changes if you can say "Yes" for specific check.
#
# 1. Only existing code has changed, no functional changes
#    If the library source code has changed but *no* new symbols were added at all
#    since the last update, then increment revision (c:r:a becomes c:r+1:a).
#    This is usually happen if the existing source of a function was changed for
#    bug fixing e.g.
#
#  --> Increase the 'LT_LIBCOAP_REVISION' value with *every* new software release
#      within one release cycle.
#
# 2. Interfaces were added, functions have changed or are removed
#    If any interfaces [exported functions or data] have been added, got internal
#    changes that implies a different behavior or removed and by this the visible
#    symbols have changed since the last update, increment current, and set
#    revision to 0 (c:r:a becomes c+1:r=0:a).
#
#  --> Increase the 'LT_LIBCOAP_CURRENT' value whenever as an interface has been added
#      or removed. This implies also a API change! You mostly have to change the
#      'libcoap_major_version' or at least 'libcoap_minor_version' then too!
#  --> Set 'LT_LIBCOAP_REVISION' to 0.
#
# 3. Interfaces were added but none removed or changed
#    If any interfaces have been added since the last public release and non of the
#    existing interfaces were removed and existing interfaces have not changed internal
#    functionality then the new library is backward compatible. Existing binaries can
#    use the new library the same than as the existing old library without loosing
#    existing functionality or breakage.
#    Increase age by 1 (c:r:a becomes c:r:a+1).
#
#  --> Increase the 'LT_LIBCOAP_AGE' value only if the changes made to the ABI are
#      backward compatible.
#
# 4. Interfaces were removed or have functional changes
#    If any interfaces within the library have been removed since the last public
#    release or got some internal changes that let the interface act different than
#    before, then set age to 0. The library isn't backwards compatible.
#
#  --> Set 'LT_LIBCOAP_AGE' to 0.

# The following explanation may help to understand the above rules a bit better:
# consider that there are three possible kinds of reactions from users of your
# library to changes in a shared library:
#
# 1. Programs using the previous version may use the new version as drop-in
#    replacement, and programs using the new version can also work with the
#    previous one. In other words, no recompiling nor relinking is needed. In this
#    case, bump 'LT_LIBCOAP_REVISION' only, don't touch 'LT_LIBCOAP_CURRENT' nor
#    'LT_LIBCOAP_AGE'.
#
# 2. Programs using the previous version may use the new version
#    as drop-in replacement, but programs using the new version may use APIs not
#    present in the previous one. In other words, a program linking against the new
#    version may fail with 'unresolved symbols' if linking against the old version
#    at runtime: set 'LT_LIBCOAP_REVISION' to 0, bump 'LT_LIBCOAP_CURRENT' and
#    'LT_LIBCOAP_AGE'.
#
# 3. Programs may need to be changed, recompiled, and relinked in
#    order to use the new version. Bump 'LT_LIBCOAP_CURRENT',
#    set 'LT_LIBCOAP_REVISION' and 'LT_LIBCOAP_AGE' to 0.

# To add to the confusion, if LIBCOAP_SO_VERSION is set to 3:0:1 (c:r:a), then the
# .so version naming ends up as 2.1.0 (c-a:a:r) (as decided by libtool).

#
# CAUTION
#
# You will need to manually update various configuration files by running the
# ./configure built script file scripts/fix_version.sh .
#

LT_LIBCOAP_CURRENT=5
LT_LIBCOAP_REVISION=0
LT_LIBCOAP_AGE=2
LIBCOAP_SO_VERSION=$LT_LIBCOAP_CURRENT.$LT_LIBCOAP_REVISION.$LT_LIBCOAP_AGE

# Announce the libtool version
AC_SUBST(LT_LIBCOAP_CURRENT)
AC_SUBST(LT_LIBCOAP_REVISION)
AC_SUBST(LT_LIBCOAP_AGE)
AC_SUBST(LIBCOAP_SO_VERSION)

# Defining the API Version
LIBCOAP_API_VERSION=3

# calculate the ABI version naming as calculated by libtool
m4_pattern_allow(LT_TEMP)
LT_TEMP=$LT_LIBCOAP_CURRENT
LT_TEMP=`expr $LT_TEMP - $LT_LIBCOAP_AGE`
if test "$LT_TEMP" != "$LIBCOAP_API_VERSION" ; then
   AC_MSG_ERROR([==> API version ($LIBCOAP_API_VERSION) does not match base of ABI ($LT_TEMP.$LT_LIBCOAP_AGE.$LT_LIBCOAP_REVISION) version.])
fi
LIBCOAP_ABI_VERSION=$LT_TEMP.$LT_LIBCOAP_AGE.$LT_LIBCOAP_REVISION
AC_SUBST(LIBCOAP_ABI_VERSION)
AC_SUBST(LIBCOAP_API_VERSION)

LT_TEMP=libcoap_release_state
if test "x$LT_TEMP" = "x"; then
    # Define a numeric version string
    m4_define([version_number],
              [m4_format([%u%03u%03u],
                         libcoap_major_version,
                         libcoap_minor_version,
                         libcoap_micro_version)])
    LIBCOAP_VERSION=version_number
    AC_SUBST(LIBCOAP_VERSION)

    # Define a base version string
    m4_define([base_version],
              [m4_format([%u.%u.%u],
                         libcoap_major_version,
                         libcoap_minor_version,
                         libcoap_micro_version)])
    LIBCOAP_PACKAGE_BASE=base_version
    AC_SUBST(LIBCOAP_PACKAGE_BASE)
else
    # Doing a rc1 etc., so not a full release, use previous full version numbers
    # Define a numeric version string
    m4_define([version_number],
              [m4_format([%u%03u%03u],
                         libcoap_pre_major_version,
                         libcoap_pre_minor_version,
                         libcoap_pre_micro_version)])
    LIBCOAP_VERSION=version_number
    AC_SUBST(LIBCOAP_VERSION)

    # Define a base version string
    m4_define([base_version],
              [m4_format([%u.%u.%u],
                         libcoap_pre_major_version,
                         libcoap_pre_minor_version,
                         libcoap_pre_micro_version)])
    LIBCOAP_PACKAGE_BASE=base_version
    AC_SUBST(LIBCOAP_PACKAGE_BASE)
fi

# Adding some default warning options for code QS
# see https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
# and http://www.gnu.org/software/automake/manual/html_node/Flag-Variables-Ordering.html
WARNING_CFLAGS="\
-pedantic \
-Wall \
-Wcast-qual \
-Wextra \
-Wformat-security \
-Winline \
-Wmissing-declarations \
-Wmissing-prototypes \
-Wnested-externs \
-Wpointer-arith \
-Wshadow \
-Wstrict-prototypes \
-Wswitch-default \
-Wswitch-enum \
-Wunused \
-Wwrite-strings \
"

# check whether or not the compiler supports -Wlogical-op (clang does not...)
AX_CHECK_COMPILE_FLAG([-Wlogical-op], [WARNING_CFLAGS="$WARNING_CFLAGS -Wlogical-op"],,[-Werror])
AX_CHECK_COMPILE_FLAG([-fdiagnostics-color], [CFLAGS="$CFLAGS -fdiagnostics-color"],,[-Werror])
AX_CHECK_COMPILE_FLAG([-Wunused-result], [WARNING_CFLAGS="$WARNING_CFLAGS -Wunused-result"])

# clang 14+ generates dwarf-5, which is not currently supported by valgrind
if test "x$CC" = "xclang"; then
    WARNING_CFLAGS="$WARNING_CFLAGS -gdwarf-4"
fi

AC_SUBST([WARNING_CFLAGS])

AX_CHECK_LINK_FLAG([-Wl,--version-script=${srcdir}/libcoap-${LIBCOAP_API_VERSION}.map],
                   [libcoap_SYMBOLS="-Wl,--version-script=\$(srcdir)/libcoap-\$(LIBCOAP_API_VERSION).map"],
                   [libcoap_SYMBOLS="-export-symbols \$(top_builddir)/libcoap-\$(LIBCOAP_API_VERSION).sym"])

AC_SUBST(libcoap_SYMBOLS)

# configure options
# __documentation__

AC_ARG_ENABLE([documentation],
              [AS_HELP_STRING([--enable-documentation],
                              [Enable building all the documentation [default=yes]])],
              [build_documentation="$enableval"],
              [build_documentation="yes"])

AM_CONDITIONAL(BUILD_DOCUMENTATION, [test "x$build_documentation" = "xyes"])

doxygen_version_required=1.7.0
dot_version_required=2.26.0

AC_ARG_ENABLE([doxygen],
              [AS_HELP_STRING([--enable-doxygen],
                              [Enable building the doxygen documentation [default=yes]])],
              [build_doxygen="$enableval"],
              [build_doxygen="yes"])

if test -z "$enable_doxygen"; then
    if test "x$enable_documentation" = "xno"; then
        build_doxygen="no"
    fi
fi

if test "x$build_doxygen" = "xyes"; then
    # Check for doxygen
    AC_PATH_PROGS([DOXYGEN], [doxygen])
    if test -z "$DOXYGEN"; then
        if test "x$build_doxygen" = "xyes"; then
            AC_MSG_WARN([==> You want to build the doxygen documentation but doxygen was not found!])
            AC_MSG_ERROR([==> Install the package that contains doxygen or disable the doxygen documentation using '--disable-doxygen'.])
        fi
    else
        AC_MSG_CHECKING([for compatible doxygen version (>= $doxygen_version_required)])
        doxygen_version=`$DOXYGEN --version`
        AS_VERSION_COMPARE([$doxygen_version],
                           [$doxygen_version_required],
                           [AC_MSG_RESULT([no])
                            DOXYGEN=""],
                           [AC_MSG_RESULT([yes $doxygen_version])],
                           [AC_MSG_RESULT([yes $doxygen_version])])
        if test "x$DOXYGEN" = "x" -a "x$build_doxygen" = "xyes"; then
            AC_MSG_WARN([==> Doxygen $doxygen_version too old. Doxygen >= $doxygen_version_required required for documentation build.])
            AC_MSG_ERROR([==> Install required doxygen version or disable the doxygen documentation using '--disable-doxygen'.])
        else
            # we found doxygen and the version is valid
            # now checking dot (needed for graphics)
            AC_PATH_PROG([DOT], [dot])
            if test "x$DOT" = "x"; then
                AC_MSG_WARN([==> dot not found - continuing without DOT support])
                AC_MSG_WARN([==> The libcoap html documentation will be build without DOT graphics!])
                HAVE_DOT="NO"
                USE_CALL_GRAPH="NO"
            else
                AC_MSG_CHECKING([for compatible dot version (>= $dot_version_required)])
                case $host in
                    *-freebsd1*)
                    # csh and tcsh have a different output redirection than more recent shells
                    # cmd >& file   # Redirect both stdout and stderr to file.
                    # cmd >>& file  # Append both stdout and stderr to file.
                    # cmd1 | cmd2   # pipe stdout to cmd2
                    # cmd1 |& cmd2  # pipe stdout and stderr to cmd2
                    # Using an explicit call with the default always available C-shell on FreeBSD,
                    # the user may have installed another shell from a port which we don't know here
                    dot_version=`export DOT=$DOT && csh -c '$DOT -V |& cut -f5 -d" "'`
                    ;;

                    *)
                    dot_version=`$DOT -V 2>&1 | cut -f5 -d" "`
                    ;;

                esac
                AS_VERSION_COMPARE([$dot_version],
                                   [$dot_version_required],
                                   [AC_MSG_RESULT([no])
                                    DOT=""],
                                   [AC_MSG_RESULT([yes $dot_version])],
                                   [AC_MSG_RESULT([yes $dot_version])])
                if test "x$DOT" = "x" -a "x$build_doxygen" = "xyes"; then
                    AC_MSG_WARN([==> Graphviz dot $dot_version too old. Graphviz >= $dot_version_required required for doxygen build.])
                    AC_MSG_ERROR([==> Install required graphviz version or disable the doxygen documentation using '--disable-doxygen'.])
                fi
                # we found dot and the version is valid
                HAVE_DOT="YES"
                # let doxygen create caller graphics
                # see http://www.stack.nl/~dimitri/doxygen/manual/config.html#cfg_call_graph
                USE_CALL_GRAPH="YES"
                # exporting the tests to doc/Doxygen(.in)
                AC_SUBST(HAVE_DOT)
                AC_SUBST(USE_CALL_GRAPH)
            fi
        fi
    fi
fi
AM_CONDITIONAL(BUILD_DOXYGEN, [test "x$build_doxygen" = "xyes"])

AM_CONDITIONAL([HAVE_DOXYGEN], [test -n "$DOXYGEN"])
AM_COND_IF([HAVE_DOXYGEN], [AC_CONFIG_FILES([doc/Doxyfile])])

# __manpages__

AC_ARG_ENABLE([manpages],
              [AS_HELP_STRING([--enable-manpages],
                              [Enable building the manpages [default=yes]])],
              [build_manpages="$enableval"],
              [build_manpages="yes"])

if test -z "$enable_manpages"; then
    if test "x$enable_documentation" = "xno"; then
        build_manpages="no"
    fi
fi

if test "x$build_manpages" = "xyes"; then
    AC_ARG_VAR([A2X], [a2x command])
    AC_PATH_PROG([A2X], [a2x])
    if test "x$A2X" = "x"; then
        AC_MSG_WARN([==> You want to build the manpages, but a2x was not found!])
        AC_MSG_ERROR([==> Install the package that contains a2x (mostly asciidoc) or disable the build of the manpages using '--disable-manpages'.])
        build_manpages="no"
    else
        AX_CHECK_A2X_TO_MANPAGE([], [
            AC_MSG_RESULT([no])
            AC_MSG_WARN([==> You want to build the manpages with a2x, but manpage formatting does not work!])
            AC_MSG_ERROR([==> Install the packages that contains the docbook DTD and XSL stylesheets (presumably docbook, docbook-xml) or disable the build of the manpages using '--disable-manpages'.])
            build_manpages="no"
        ])
    fi
fi
AM_CONDITIONAL(BUILD_MANPAGES, [test "x$build_manpages" = "xyes"])

# configure options
# __dtls__
# The Datagram Transport Layer Security (DTLS) feature needs cryptography
# functions.
# We currently support the GnuTLS and OpenSSL library. The user can preselect
# the cryptography library that should be used by adding '--with-gnutls' or
# '--with-openssl'.
# If the user isn't using a selection we first search for GnuTLS and fallback
# to OpenSSL if the GnuTLS library couldn't be found.

gnutls_version_required=3.3.0
openssl_version_required=1.1.0
mbedtls_version_required=2.7.10
wolfssl_version_required=5.2.0
tinydtls_version_required=0.8.6

AC_ARG_ENABLE([dtls],
              [AS_HELP_STRING([--enable-dtls],
                              [Enable building with DTLS support [default=yes]])],
              [build_dtls="$enableval"],
              [build_dtls="yes"])

AC_ARG_WITH([gnutls],
            [AS_HELP_STRING([--with-gnutls],
                            [Use GnuTLS for DTLS functions])],
            [with_gnutls="$withval"],
            [with_gnutls="no"])

AC_ARG_WITH([openssl],
            [AS_HELP_STRING([--with-openssl],
                            [Use OpenSSL for DTLS functions])],
            [with_openssl="$withval"],
            [with_openssl="no"])

AC_ARG_WITH([wolfssl],
            [AS_HELP_STRING([--with-wolfssl],
                            [Use wolfSSL for DTLS functions])],
            [with_wolfssl="$withval"],
            [with_wolfssl="no"])

AC_ARG_WITH([mbedtls],
            [AS_HELP_STRING([--with-mbedtls],
                            [Use Mbed TLS for DTLS functions])],
            [with_mbedtls="$withval"],
            [with_mbedtls="no"])

AC_ARG_WITH([tinydtls],
           [AS_HELP_STRING([--with-tinydtls],
                           [Use TinyDTLS for DTLS functions])],
           [with_tinydtls="$withval"],
           [with_tinydtls="no"])

AC_ARG_WITH([submodule-tinydtls],
           [AS_HELP_STRING([--with-submodule-tinydtls],
                           [Use the TinyDTLS provided in the git submodule over the system-provided version [default=fallback to submodule if --with-tinydtls is explicitly set and no system-provided version was found])])],
           [with_submodule_tinydtls="$withval"],
           [with_submodule_tinydtls="explicit_fallback"])

if test "x$with_gnutls" = "xyes" -o "x$with_openssl" = "xyes" -o "x$with_wolfssl" = "xyes" -o "x$with_mbedtls" = "xyes" -o "x$with_tinydtls" = "xyes"; then
    if test "x$build_dtls" = "xno"; then
        # Give an advice that '--with_gnutls', '--with_openssl', '--with_wolfssl', '--with-mbedtls' or '--with-tinydtls' was used but
        # DTLS support isn't configured.
        AC_MSG_WARN([==> Using the configure options '--with-gnutls', '--with-openssl', '--with_wolfssl', '--with-mbedtls' or '--with-tinydtls' without '--enable-dtls' is useless and will be ignored.])
    fi
fi
if test "x$with_submodule_tinydtls" = "xyes"; then
    if test "x$with_tinydtls" = "xno"; then
        # Give an advice that '--with-submodule-tinydtls' is useless if tinydtls is not also enabled.
        AC_MSG_WARN([==> Using the configure option '--with-submodule-tinydtls' without '--with-tinydtls' is useless and it will be ignored.])
    fi
fi

# O.K. the user hasn't de-selected DTLS
if test "x$build_dtls" = "xyes"; then
    # The user can't select multiple crypto libraries.
    TLSCOUNT=0
    if test "x$with_gnutls" = "xyes"; then
        TLSCOUNT=`expr $TLSCOUNT + 1`
    fi
    if test "x$with_openssl" = "xyes"; then
        TLSCOUNT=`expr $TLSCOUNT + 1`
    fi
    if test "x$with_wolfssl" = "xyes"; then
        TLSCOUNT=`expr $TLSCOUNT + 1`
    fi
    if test "x$with_mbedtls" = "xyes"; then
        TLSCOUNT=`expr $TLSCOUNT + 1`
    fi
    if test "x$with_tinydtls" = "xyes"; then
        TLSCOUNT=`expr $TLSCOUNT + 1`
    fi
    if test "$TLSCOUNT" -gt 1; then
        AC_MSG_ERROR([==> You can't use more than 1 of the options '--with-gnutls', '--with-openssl', '--with-mbedtls' or '--with-tinydtls' at the same time while '--enable-dtls' is selected!
                  ==> Please note, the option '--enable-dtls' is turned on by default if not explicitly disabled!])
    fi

    # Check for all possible usable and supported SSL crypto libraries
    # GnuTLS
    PKG_CHECK_MODULES([GnuTLS],
                      [gnutls],
                      [have_gnutls="yes"],
                      [have_gnutls="no"])

    # OpenSSL
    PKG_CHECK_MODULES([OpenSSL],
                      [openssl],
                      [have_openssl="yes"],
                      [have_openssl="no"])

    # wolfSSL
    PKG_CHECK_MODULES([wolfSSL],
                  [wolfssl],
                  [have_wolfssl="yes"],
                  [have_wolfssl="no"])

    # Mbed TLS
    if test "x${MbedTLS_CFLAGS+set}" = "xset"; then
        mbedtls_cflags_overridden="yes"
    else
        mbedtls_cflags_overridden="no"
    fi

    if test "x${MbedTLS_LIBS+set}" = "xset"; then
        mbedtls_libs_overridden="yes"
    else
        mbedtls_libs_overridden="no"
    fi

    # If MbedTLS_CFLAGS and MbedTLS_LIBS are overridden, pkg-config will always assume the library was found, even
    # though MbedTLS doesn't necessarily have a pkg-config file. Therefore, we might as well use the "old" way to
    # determine whether we can link MbedTLS (and which version we have).
    if test "x$mbedtls_libs_overridden" = "xyes" -a "x$mbedtls_cflags_overridden" = "xyes"; then
      have_mbedtls="no"
      mbedtls_has_pkgconfig="no"
    else
      # Attempt to find MbedTLS using pkg-config.

      # When statically linking against libcoap, all transitive dependencies need to be specified as linker flags
      # as well. Use pkg-config --static for that.
      if test "x$enable_static" = "xyes"; then
        KEEP_PKG_CONFIG=$PKG_CONFIG
        PKG_CONFIG="$PKG_CONFIG --static"
        PKG_CHECK_MODULES([MbedTLS],
                          [mbedtls],
                          [have_mbedtls="yes"; mbedtls_has_pkgconfig="yes"],
                          [have_mbedtls="no"; mbedtls_has_pkgconfig="no"])
        PKG_CONFIG=$KEEP_PKG_CONFIG
      else
        PKG_CHECK_MODULES([MbedTLS],
                          [mbedtls],
                          [have_mbedtls="yes"; mbedtls_has_pkgconfig="yes"],
                          [have_mbedtls="no"; mbedtls_has_pkgconfig="no"])
      fi
    fi

    if test "x$have_mbedtls" = "xno"; then
      # Attempt to find mbedtls without pkg-config.

      # default linker flags (default CFLAGS are empty, so they don't need to be set).
      if test "x$mbedtls_libs_overridden" == "xno"; then
        MbedTLS_LIBS="-lmbedtls -lmbedcrypto -lmbedx509"
      fi

      # check whether we can find MbedTLS
      local_MbedTLS_save_CFLAGS=$CFLAGS
      CFLAGS="$MbedTLS_CFLAGS $CFLAGS"
      local_MbedTLS_save_LIBS=$LIBS
      LIBS="$MbedTLS_LIBS $LIBS"
      AC_CHECK_LIB(mbedtls, mbedtls_version_get_string,
                   [have_mbedtls="yes"],
                   [have_mbedtls="no"])
      LIBS=$local_MbedTLS_save_LIBS
      CFLAGS=$local_MbedTLS_save_CFLAGS
    fi

    # here, we know whether we can find MbedTLS, but need to determine the version.
    if test "x$have_mbedtls" = "xyes"; then
        if test "x$mbedtls_has_pkgconfig" = "xyes"; then
          # If pkg-config found mbedtls, use it to determine the version.
          mbedtls_version=`$PKG_CONFIG --modversion mbedtls`;
        elif test "x$cross_compiling" = "xyes" ; then
            # Have no option but to do this
            mbedtls_version=$mbedtls_version_required
        else
            # Get actual library version by compiling a test program.
            local_MbedTLS_save_CFLAGS=$CFLAGS
            CFLAGS="$MbedTLS_CFLAGS $CFLAGS"
            local_MbedTLS_save_LIBS=$LIBS
            LIBS="$MbedTLS_LIBS $LIBS"
            AC_LANG_PUSH(C)
            AC_LINK_IFELSE([dnl
                AC_LANG_SOURCE(
                    [[#include <stdio.h>
                     #include <mbedtls/version.h>
                     int main () {
                       char str[20];
                       mbedtls_version_get_string(str);
                       fprintf(stdout,"%s\n",str);
                       return 0;
                     }]])],
               [mbedtls_version=$(./conftest$EXEEXT)],
               [AC_MSG_WARN(Failed to determine Mbed TLS version)
                have_mbedtls=no])
            AC_LANG_POP(C)
            LIBS=$local_MbedTLS_save_LIBS
            CFLAGS=$local_MbedTLS_save_CFLAGS
        fi
    fi

    if test "${TinyDTLS_CFLAGS+set}" = "set"; then
        tinydtls_cflags_overridden="yes"
    fi
    if test "${TinyDTLS_LIBS+set}" = "set"; then
        tinydtls_libs_overridden="yes"
    fi
    # TinyDTLS
    PKG_CHECK_MODULES([TinyDTLS],
                      [tinydtls],
                      [have_tinydtls="yes"],
                      [have_tinydtls="no"])

    # TBD ?

    # The user wants to use explicit GnuTLS if '--with-gnutls' was set.
    if test "x$with_gnutls" = "xyes"; then
        # Some more sanity checking.
        if test "x$have_gnutls" != "xyes"; then
            AC_MSG_ERROR([==> You want to build libcoap with DTLS support by the GnuTLS library but pkg-config file 'gnutls.pc' could not be found!
                      Install the package(s) that contains the development files for GnuTLS,
                      or select a different TLS library or disable the DTLS support using '--disable-dtls'.])
        fi
        AC_MSG_NOTICE([The use of GnuTLS was explicitly requested with configure option '--with-gnutls'!])

        # check for valid GnuTLS version
        gnutls_version=`$PKG_CONFIG --modversion gnutls`
        AX_CHECK_GNUTLS_VERSION
        have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
    fi

    # The user wants to use explicit OpenSSL if '--with-openssl was set'.
    if test "x$with_openssl" = "xyes"; then
        # Some more sanity checking.
        if test "x$have_openssl" != "xyes"; then
            AC_MSG_ERROR([==> You want to build libcoap with DTLS support by the OpenSSL library but pkg-config file 'openssl.pc' could not be found!
                      Install the package(s) that contains the development files for OpenSSL,
                      or select a different TLS library or disable the DTLS support using '--disable-dtls'.])
        fi
        AC_MSG_NOTICE([The use of OpenSSL was explicitly requested with configure option '--with-openssl'!])

        # check for valid OpenSSL version
        openssl_version=`$PKG_CONFIG --modversion openssl`
        AX_CHECK_OPENSSL_VERSION
        have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
    fi

    # The user wants to use explicit wolfSSL if '--with-wolfssl' was set.
    if test "x$with_wolfssl" = "xyes"; then
        # Some more sanity checking.
        if test "x$have_wolfssl" != "xyes"; then
            AC_MSG_ERROR([==> You want to build libcoap with DTLS support by the wolfSSL library but pkg-config file 'wolfssl.pc' could not be found!
                    Install the package(s) that contains the development files for wolfSSL,
                    or select a different TLS library or disable the DTLS support using '--disable-dtls'.])
        fi
        AC_MSG_NOTICE([The use of wolfSSL was explicitly requested with configure option '--with-wolfssl'!])

        # check for valid wolfSSL version
        wolfssl_version=`$PKG_CONFIG --modversion wolfssl`
        AX_CHECK_WOLFSSL_VERSION
        have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
    fi

    # The user wants to use explicit Mbed TLS if '--with-mbedtls was set'.
    if test "x$with_mbedtls" = "xyes"; then
        # Some more sanity checking.
        if test "x$have_mbedtls" != "xyes"; then
            AC_MSG_ERROR([==> You want to build libcoap with DTLS support by the Mbed TLS library but library 'mbedtls' could not be found!
                      Install the package(s) that contains the development files for Mbed TLS,
                      or select a different TLS library or disable the DTLS support using '--disable-dtls'.])
        fi
        AC_MSG_NOTICE([The use of Mbed TLS was explicitly requested with configure option '--with-mbedtls'!])

        # mbedtls_version determined previously
        AX_CHECK_MBEDTLS_VERSION
        have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
    fi

    # The user wants to use explicit TinyDTLS if '--with-tinydtls was set'.
    if test "x$with_tinydtls" = "xyes" ; then
        AC_MSG_NOTICE([The use of TinyDTLS was explicitly requested with configure option '--with-tinydtls'!])
        if [ test "x$have_tinydtls" = "xno" ] && [ test "x$with_submodule_tinydtls" = "xexplicit_fallback" ]  || [ test "x$with_submodule_tinydtls" = "xyes" ]; then
            AC_MSG_NOTICE([Using TinyDTLS submodule over system-provided version because either "--with-submodule-tinydtls" was set or no system-provided TinyDTLS was found.])
            if test -e "$srcdir/ext/tinydtls/dtls.h"; then
               AC_CONFIG_SUBDIRS([ext/tinydtls])
               if test "x$enable_shared" = "xyes"; then
                   auto_TinyDTLS_LIBS="-L\$(top_builddir)/ext/tinydtls -ltinydtls"
               else
                   # Needed as TinyDTLS compiling does not recognize --disable-shared
                   # and still builds libtinydtls.so which gets linked in otherwise
                   auto_TinyDTLS_LIBS="-L\$(top_builddir)/ext/tinydtls -l:libtinydtls.a"
               fi
               have_submodule_tinydtls="yes"

               auto_TinyDTLS_CFLAGS="-I \$(top_srcdir)/ext -I \$(top_srcdir)/ext/tinydtls"

               if test "x$tinydtls_cflags_overridden" != "xyes";  then
                   TinyDTLS_CFLAGS="$auto_TinyDTLS_CFLAGS"
               fi
               if test "x$tinydtls_libs_overridden" != "xyes";  then
                   TinyDTLS_LIBS="$auto_TinyDTLS_LIBS"
               fi
               # 'git submodule update' may be required
               AC_DEFINE(HAVE_DTLS_SET_LOG_HANDLER, [1], [Define to 1 if TinyDTLS has dtls_set_log_handler.])
            else
                AC_MSG_ERROR([==> You want to build libcoap with DTLS support using the TinyDTLS submodule library but no suitable version could be found!
                            Check whether you have updated the TinyDTLS git submodule, use the system-provided version if available (set '--with-submodule-tinydtls=no'),
                            select a different TLS library or disable the DTLS support using '--disable-dtls'.])
                have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
                have_submodule_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
            fi
        elif test "x$have_tinydtls" = "xyes"; then
            AC_MSG_NOTICE([Using system-provided TinyDTLS])
            tinydtls_version=`$PKG_CONFIG --modversion tinydtls`
            AX_CHECK_TINYDTLS_VERSION
            AC_CHECK_LIB(tinydtls,dtls_set_log_handler,AC_DEFINE(HAVE_DTLS_SET_LOG_HANDLER, [1], [Define to 1 if TinyDTLS has dtls_set_log_handler.]))
        else
            AC_MSG_ERROR([==> You want to build libcoap with DTLS support using the TinyDTLS library but no suitable version could be found!
                        Use the submodule TinyDTLS version (set '--with-submodule-tinydtls=yes' and update the git submodule),
                        ensure that you have a system-provided version of TinyDTLS that can be found using pkg-config (older versions can not),
                        select a different TLS library or disable the DTLS support using '--disable-dtls'.])
            have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script
        fi

        have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
    fi

    if test "$TLSCOUNT" -eq 0; then
      # The user hasn't requested the use of a specific cryptography library
      # we try first GnuTLS for usability ...
      if test "x$have_gnutls" = "xyes"; then
          gnutls_version=`$PKG_CONFIG --modversion gnutls`
          AX_CHECK_GNUTLS_VERSION
          AC_MSG_NOTICE([Using auto selected library GnuTLS for DTLS support!])
          with_gnutls_auto="yes"
          have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script

      # ... and if not found check OpenSSL is suitable.
      elif test "x$have_openssl" = "xyes"; then
          openssl_version=`$PKG_CONFIG --modversion openssl`
          AX_CHECK_OPENSSL_VERSION
          AC_MSG_NOTICE([Using auto selected library OpenSSL for DTLS support!])
          with_openssl_auto="yes"
          have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script

      # ... and if not found, check if wolfSSL is suitable.
      elif test "x$have_wolfssl" = "xyes"; then
          wolfssl_version=`$PKG_CONFIG --modversion wolfssl`
          AX_CHECK_WOLFSSL_VERSION
          AC_MSG_NOTICE([Using auto selected library wolfSSL for DTLS support!])
          with_wolfssl_auto="yes"
          have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script

      # ... and if not found check Mbed TLS is suitable.
      elif test "x$have_mbedtls" = "xyes"; then
          # Mbed TLS [does not have mbedtls.pc pkg-config file]
          # mbedtls_version determined previously
          AX_CHECK_MBEDTLS_VERSION
          AC_MSG_NOTICE([Using auto selected library Mbed TLS for DTLS support!])
          with_mbedtls_auto="yes"
          have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
          have_tinydtls="no" # don't confuse AC_MSG_RESULT at the end of the script

      elif [ test "x$with_tinydtls" = "xyes" ] && [ test "x$have_tinydtls" = "xyes" ]; then
        AC_MSG_NOTICE([Using auto selected library TinyDTLS for DTLS support!])
        tinydtls_version=`$PKG_CONFIG --modversion tinydtls`
        AX_CHECK_TINYDTLS_VERSION
        with_tinydtls_auto="yes"
        have_gnutls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_mbedtls="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_openssl="no" # don't confuse AC_MSG_RESULT at the end of the script
        have_wolfssl="no" # don't confuse AC_MSG_RESULT at the end of the script

      # Note that the TinyDTLS submodule is used only when explicitly requested.
      # Giving out an error message if we haven't found at least one crypto library.
      else
          AC_MSG_ERROR([==> Option '--enable-dtls' is set but none of the needed cryptography libraries GnuTLS, OpenSSL, wolfSSL, Mbed TLS or TinyDTLS could be found!
                        Install at least one of the package(s) that contains the development files for GnuTLS (>= $gnutls_version_required), OpenSSL(>= $openssl_version_required), wolfSSL(>= $wolfssl_version_required), Mbed TLS(>= $mbedtls_version_required), or TinyDTLS(>= $tinydtls_version_required)
                        or disable the DTLS support using '--disable-dtls'.])
      fi
    fi

    # Saving the DTLS related Compiler flags.
    if test "x$with_gnutls" = "xyes" -o "x$with_gnutls_auto" = "xyes"; then
        DTLS_CFLAGS="$GnuTLS_CFLAGS"
        DTLS_LIBS="$GnuTLS_LIBS"
        AC_DEFINE(COAP_WITH_LIBGNUTLS, [1], [Define to 1 if the system has libgnutls28.])
    fi
    if test "x$with_openssl" = "xyes" -o "x$with_openssl_auto" = "xyes"; then
        DTLS_CFLAGS="$OpenSSL_CFLAGS"
        DTLS_LIBS="$OpenSSL_LIBS"
        AC_DEFINE(COAP_WITH_LIBOPENSSL, [1], [Define to 1 if the system has libssl1.1.])
    fi
    if test "x$with_wolfssl" = "xyes" -o "x$with_wolfssl_auto" = "xyes"; then
        DTLS_CFLAGS="$wolfSSL_CFLAGS"
        DTLS_LIBS="$wolfSSL_LIBS"
        AC_DEFINE(COAP_WITH_LIBWOLFSSL, [1], [Define to 1 if the system has libwolfssl.])
    fi
    if test "x$with_mbedtls" = "xyes" -o "x$with_mbedtls_auto" = "xyes"; then
        DTLS_CFLAGS="$MbedTLS_CFLAGS"
        DTLS_LIBS="$MbedTLS_LIBS"
        AC_DEFINE(COAP_WITH_LIBMBEDTLS, [1], [Define to 1 if the system has libmbedtls2.7.10.])
    fi
    if test "x$with_tinydtls" = "xyes" -o "x$with_tinydtls_auto" = "xyes"; then
        DTLS_CFLAGS="$TinyDTLS_CFLAGS"
        DTLS_LIBS="$TinyDTLS_LIBS"
        AC_DEFINE(COAP_WITH_LIBTINYDTLS, [1], [Define to 1 if the system has libtinydtls.])
    fi
    AC_SUBST(DTLS_CFLAGS)
    AC_SUBST(DTLS_LIBS)
fi

# Define the Library name extension for the TLS the library was linked against
if test "x$with_openssl" = "xyes" -o "x$with_openssl_auto" = "xyes"; then
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-openssl
elif test "x$with_wolfssl" = "xyes" -o "x$with_wolfssl_auto" = "xyes"; then
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-wolfssl
elif test "x$with_gnutls" = "xyes" -o "x$with_gnutls_auto" = "xyes"; then
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-gnutls
elif test "x$with_mbedtls" = "xyes" -o "x$with_mbedtls_auto" = "xyes"; then
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-mbedtls
elif test "x$with_tinydtls" = "xyes"; then
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-tinydtls
else
    LIBCOAP_DTLS_LIB_EXTENSION_NAME=-notls
    AC_DEFINE(HAVE_NOTLS, [1], [Define to 1 if libcoap has no tls library support.])
fi
AM_CONDITIONAL(HAVE_NOTLS, [test "x$LIBCOAP_DTLS_LIB_EXTENSION_NAME" = "x-notls"])

LIBCOAP_NAME_SUFFIX="$LIBCOAP_API_VERSION$LIBCOAP_DTLS_LIB_EXTENSION_NAME"

AC_SUBST(LIBCOAP_NAME_SUFFIX)
AC_SUBST(LIBCOAP_DTLS_LIB_EXTENSION_NAME)
AC_SUBST([DOLLAR_SIGN],[$])

# configure options
# __OSCORE__
# Support for Object Security according to RFC 8613.
AC_ARG_ENABLE([oscore],
              [AS_HELP_STRING([--enable-oscore],
                              [Enable building with OSCORE support [default=yes]])],
              [build_oscore="$enableval"],
              [build_oscore="yes"])

if test "x$build_oscore" = "xyes"; then
    if test "x$LIBCOAP_DTLS_LIB_EXTENSION_NAME" = "x-notls"; then
        AC_MSG_WARN([==> --enable-oscore requires crypto support from TLS library or OS])
    fi
fi

if test "x$build_oscore" = "xyes"; then
        AC_DEFINE(COAP_OSCORE_SUPPORT, [1], [Define to 1 to build with OSCORE support.])
fi
AM_CONDITIONAL(COAP_OSCORE_SUPPORT, [test "x$build_oscore" = "xyes"])

# configure options
# __tests__
AC_ARG_ENABLE([tests],
              [AS_HELP_STRING([--enable-tests],
                              [Enable building the binary testsuite. Requires --enable-static  [default=no]])],
              [build_tests="$enableval"],
              [build_tests="no"])

if test "x$build_tests" = "xyes"; then
    PKG_CHECK_MODULES([CUNIT],
                      [cunit],
                      [have_cunit=yes
                       AC_DEFINE(HAVE_LIBCUNIT, [1], [Define to 1 if the system has libcunit.])],
                      [have_cunit=no
                       AC_MSG_WARN([==> You want to build the testing binary but the pkg-config file cunit.pc could not be found or installed CUnit version is too old!])
                       AC_MSG_ERROR([==> Install the package(s) that contains the development files for CUnit or disable the testing binary using '--disable-tests'.])
                      ])
    if test "x$enable_static" = "xno"; then
        enable_static=yes
        AC_MSG_WARN([--enable-tests requires --enable-static which is now enabled.])
    fi
fi
AM_CONDITIONAL(HAVE_CUNIT, [test "x$CUNIT_LIBS" != "x"])

# configure options
# __examples__
AC_ARG_ENABLE([examples],
              [AS_HELP_STRING([--enable-examples],
                              [Enable building the example binaries [default=yes]])],
              [build_examples="$enableval"],
              [build_examples="yes"])

AM_CONDITIONAL(BUILD_EXAMPLES, [test "x$build_examples" = "xyes"])

# configure options
# __examples-source
AC_ARG_ENABLE([examples-source],
              [AS_HELP_STRING([--enable-examples-source],
                              [Enable installing example source to DATAROOTDIR/libcoap/examples [default=yes]])],
              [build_examples_source="$enableval"],
              [build_examples_source="yes"])

AM_CONDITIONAL(BUILD_EXAMPLES_SOURCE, [test "x$build_examples_source" = "xyes"])

# configure options
# __gcov__
AC_ARG_ENABLE([gcov],
              [AS_HELP_STRING([--enable-gcov],
                              [Enable building with gcov test coverage support [default=no]])],
              [build_gcov="$enableval"],
              [build_gcov="no"
               AC_MSG_WARN([gcov is disabled])
              ])

if test "x$build_gcov" = "xyes"; then
   if test "x$GCC" != "xyes"; then
        AC_MSG_ERROR([Currently, gcov is assumed to work with GCC-compatible compilers only.])
   else
        AX_CHECK_COMPILE_FLAG([-fprofile-arcs], [CFLAGS="$CFLAGS -fprofile-arcs"])
        AX_CHECK_COMPILE_FLAG([-ftest-coverage], [CFLAGS="$CFLAGS -ftest-coverage"])
        # FIXME: clang complains about '--coverage'
        AX_CHECK_COMPILE_FLAG([--coverage], [CFLAGS="$CFLAGS --coverage -O0" LDFLAGS="$LDFLAGS --coverage"])
   fi
fi

# configure options
# __license-install__
AC_ARG_ENABLE([license-install],
              [AS_HELP_STRING([--enable-license-install],
                              [Enable installing LICENSE to DOCDIR [default=yes]])],
              [build_license_install="$enableval"],
              [build_license_install="yes"])

AM_CONDITIONAL(BUILD_LICENSE_INSTALL, [test "x$build_license_install" = "xyes"])

# configure options
# __ipv4__
AC_ARG_ENABLE([ipv4],
              [AS_HELP_STRING([--enable-ipv4-support],
                              [Enable building with support for IPv4 packets [default=yes]])],
              [build_ipv4_support="$enableval"],
              [build_ipv4_support="yes"])

AS_IF([test "x$build_ipv4_support" = "xyes"],
      [AC_DEFINE(COAP_IPV4_SUPPORT, [1], [Define to build support for IPv4 packets.])])

# configure options
# __ipv6__
AC_ARG_ENABLE([ipv6],
              [AS_HELP_STRING([--enable-ipv6-support],
                              [Enable building with support for IPv6 packets [default=yes]])],
              [build_ipv6_support="$enableval"],
              [build_ipv6_support="yes"])

AS_IF([test "x$build_ipv6_support" = "xyes"],
      [AC_DEFINE(COAP_IPV6_SUPPORT, [1], [Define to build support for IPv6 packets.])])

# configure options
# __af_unix__
AC_ARG_ENABLE([af_unix],
              [AS_HELP_STRING([--enable-af-unix-support],
                              [Enable building with support for Unix socket packets [default=yes]])],
              [build_af_unix_support="$enableval"],
              [build_af_unix_support="yes"])

AS_IF([test "x$build_af_unix_support" = "xyes"],
      [AC_DEFINE(COAP_AF_UNIX_SUPPORT, [1], [Define to build support for Unix socket packets.])])

# configure options
# __tcp__
AC_ARG_ENABLE([tcp],
              [AS_HELP_STRING([--enable-tcp],
                              [Enable building with TCP support [default=yes]])],
              [build_tcp="$enableval"],
              [build_tcp="yes"])

AC_DEFINE(COAP_DISABLE_TCP, [0], [Define to 1 to build without TCP support.])
AS_IF([test "x$build_tcp" != "xyes"], [AC_DEFINE(COAP_DISABLE_TCP, [1])])
AC_SUBST(COAP_DISABLE_TCP)

# configure options
# __websockets__
AC_ARG_ENABLE([websockets],
              [AS_HELP_STRING([--enable-websockets],
                              [Enable building with WebSockets support [default=yes]])],
              [build_ws="$enableval"],
              [build_ws="yes"])

if test "x$build_ws" = "xyes"; then
    if test "x$build_tcp" != "xyes"; then
        build_ws=no
        AC_MSG_WARN([--enable-websockets requires --enable-tcp, so --enable-websockets ignored.])
    fi
fi

AS_IF([test "x$build_ws" = "xyes"],
      [AC_DEFINE(COAP_WS_SUPPORT, [1], [Define to 1 to build with WebSockets support.])])
AC_SUBST(COAP_WS_SUPPORT)

# configure options
# __async__
AC_ARG_ENABLE([async],
              [AS_HELP_STRING([--enable-async],
                              [Enable building with support for async separate responses [default=yes]])],
              [build_async="$enableval"],
              [build_async="yes"])

AS_IF([test "x$build_async" = "xyes"],
      [AC_DEFINE(COAP_ASYNC_SUPPORT, [1], [Define to 1 to build with support for async separate responses.])])

# configure options
# __observe_persist__
AC_ARG_ENABLE([async],
              [AS_HELP_STRING([--enable-observe-persist],
                              [Enable building with support for persisting observes over a server restart [default=yes]])],
              [build_observe_persist="$enableval"],
              [build_observe_persist="yes"])

AS_IF([test "x$build_observe_persist" = "xyes"],
      [AC_DEFINE(COAP_WITH_OBSERVE_PERSIST, [1], [Define to 1 to build support for persisting observes.])])

# configure options
# __q_block__
# Support for Q-Block according to RFC 9177.
AC_ARG_ENABLE([q-block],
              [AS_HELP_STRING([--enable-q-block],
                              [Enable building with Q-Block support [default=yes]])],
              [build_q_block="$enableval"],
              [build_q_block="yes"])

AS_IF([test "x$build_q_block" = "xyes"],
     [AC_DEFINE(COAP_Q_BLOCK_SUPPORT, [1], [Define to 1 to build with Q-Block support.])])

# configure options
# __add_default_names__
AC_ARG_ENABLE([add-default-names],
              [AS_HELP_STRING([--enable-add-default-names],
                              [Enable adding libraries / examples with default names [default=yes]])],
              [build_add_default_names="$enableval"],
              [build_add_default_names="yes"])

AM_CONDITIONAL(BUILD_ADD_DEFAULT_NAMES, [test "x$build_add_default_names" = "xyes"])

# end configure options
#######################

###########################################
# from configure options independent checks

# Check for (ex)ctags binary
# The needed ctags binary name differs on FreeBSD and Linux, on Linux
# systems we search for 'ctags', on FreeBSD for 'exctags'
case $host in
    # FreeBSD has exctags from the ctags port
    *-freebsd1*)
    AC_ARG_VAR([CTAGS_PROG],[the 'exctags' program to use for make target 'update-map-file'])
    AC_PATH_PROG([CTAGS_PROG],[exctags])
    ;;

    *)
    # Linux distributions have exuberant-ctags
    AC_ARG_VAR([CTAGS_PROG],[the 'ctags' program to use for make target 'update-map-file'])
    AC_PATH_PROG([CTAGS_PROG],[ctags])
    ;;

esac

if test "x$CTAGS_PROG" = "x"; then
    AC_MSG_NOTICE([==> Note: '(ex)ctags' command not found!])
    AC_MSG_WARN([==> Without ctags you will be unable to run the target 'update-map-file'!])
    AC_MSG_WARN([==> This is no problem if you just want to build the library libcoap.])
else
    if test "`$CTAGS_PROG --help | grep '\--<LANG>-kinds'`" = ""; then
        AC_MSG_NOTICE([==> Note: Your ctags binary does not support '--c-kinds'!])
        AC_MSG_NOTICE([==> Most likely, you are using the GNU Emacs ctag and not exuberant ctag.])
        AC_MSG_WARN([==> This option is required for the target 'update-map-file'.])
        AC_MSG_WARN([==> which is not a problem if you just want to build the library libcoap.])
    fi
fi

# Checks for header files.
AC_CHECK_HEADERS([assert.h arpa/inet.h limits.h netdb.h netinet/in.h \
                  pthread.h errno.h winsock2.h ws2tcpip.h \
                  stdlib.h string.h strings.h sys/socket.h sys/time.h \
                  time.h unistd.h sys/unistd.h sys/ioctl.h net/if.h ifaddrs.h])

# For epoll, need two headers (sys/epoll.h sys/timerfd.h), but set up one #define
AC_CHECK_HEADER([sys/epoll.h])
AC_CHECK_HEADER([sys/timerfd.h])
if test "x$ac_cv_header_sys_epoll_h" = "xyes" -a "x$ac_cv_header_sys_timerfd_h" = "xyes"; then
    have_epoll="yes"
    AC_ARG_WITH([epoll],
            [AS_HELP_STRING([--with-epoll],
                            [Use epoll for I/O handling [if O/S supports it]])],
            [with_epoll="$withval"],
            [with_epoll="yes"])
else
    have_epoll="no"
    if test "x$with_epoll" = "xyes"; then
        AC_MSG_WARN([==> Underlying O/S does not support epoll - --with-epoll ignored.])
        with_epoll="no"
    fi
fi

if test "x$with_epoll" = "xyes"; then
    AC_DEFINE(COAP_EPOLL_SUPPORT, 1, [Define to 1 if the system has epoll support.])
fi

AC_ARG_ENABLE([thread-safe],
        [AS_HELP_STRING([--enable-thread-safe],
                        [Enable building with thread safe support [default=yes]])],
        [enable_thread_safe="$enableval"],
        [enable_thread_safe="yes"])

if test "x$enable_thread_safe" = "xyes"; then
    AC_DEFINE(COAP_THREAD_SAFE, 1, [Define to 1 if libcoap has thread safe support])
fi

AC_ARG_ENABLE([thread-recursive-lock-detection],
        [AS_HELP_STRING([--enable-thread-recursive-lock-detection],
                        [Enable building with thread recursive locking detection support [default=yes]])],
        [enable_recursive_detection="$enableval"],
        [enable_recursive_detection="yes"])

if test "x$enable_recursive_detection" = "xyes"; then
    AC_DEFINE(COAP_THREAD_RECURSIVE_CHECK, 1, [Define to 1 detect recursive locking detection support])
fi

AC_ARG_ENABLE([small-stack],
        [AS_HELP_STRING([--enable-small-stack],
                        [Use small-stack if the available stack space is restricted [default=no]])],
        [enable_small_stack="$enableval"],
        [enable_small_stack="no"])

if test "x$enable_small_stack" = "xyes"; then
    AC_DEFINE(COAP_CONSTRAINED_STACK, 1, [Define to 1 if the system has small stack size.])
fi

AC_ARG_ENABLE([server-mode],
        [AS_HELP_STRING([--enable-server-mode],
                        [Enable CoAP server mode supporting code [default=yes]])],
        [enable_server_mode="$enableval"],
        [enable_server_mode="yes"])

if test "x$enable_server_mode" = "xyes"; then
    AC_DEFINE(COAP_SERVER_SUPPORT, 1, [Define to 1 if libcoap supports server mode code.])
fi
AM_CONDITIONAL(HAVE_SERVER_SUPPORT, [test "x$enable_server_mode" = "xyes"])

AC_ARG_ENABLE([client-mode],
        [AS_HELP_STRING([--enable-client-mode],
                        [Enable CoAP client mode supporting code [default=yes]])],
        [enable_client_mode="$enableval"],
        [enable_client_mode="yes"])

if test "x$enable_client_mode" = "xyes"; then
    AC_DEFINE(COAP_CLIENT_SUPPORT, 1, [Define to 1 if libcoap supports client mode code.])
fi
AM_CONDITIONAL(HAVE_CLIENT_SUPPORT, [test "x$enable_client_mode" = "xyes"])
if test "x$enable_server_mode" != "xyes" -a "x$enable_client_mode" != "xyes" ; then
    AC_MSG_ERROR([==> One or both of '--enable-server-mode' and '--enable-client-mode' need to be set!])
fi

AC_ARG_ENABLE([proxy-code],
        [AS_HELP_STRING([--enable-proxy-code],
                        [Enable CoAP proxy supporting code [default=yes]])],
        [enable_proxy_code="$enableval"],
        [enable_proxy_code="yes"])

if test "x$enable_proxy_code" = "xyes"; then
    if test "x$enable_server_mode" != "xyes" -o "x$enable_client_mode" != "xyes" ; then
        AC_MSG_WARN([==> Both of '--enable-server-mode' and '--enable-client-mode' need to be set for --enable-proxy-code!])
        enable_proxy_code="no"
    fi
fi
if test "x$enable_proxy_code" = "xyes"; then
    AC_DEFINE(COAP_PROXY_SUPPORT, 1, [Define to 1 if libcoap supports proxy code.])
fi

AC_ARG_ENABLE([max-logging-level],
        [AS_HELP_STRING([--enable-max-logging-level],
                        [Only build logging code up to and including the specified logging level [default=8]])],
        [enable_max_logging_level="$enableval"],
        [enable_max_logging_level="8"])

if test "x$enable_max_logging_level" != "x8"; then
    case x$enable_max_logging_level in
        x0) ;;
        x1) ;;
        x2) ;;
        x3) ;;
        x4) ;;
        x5) ;;
        x6) ;;
        x7) ;;
        *)
        AC_MSG_ERROR([--emable-max-logging-level must have a value of 0 through 8 inclusive])
        ;;
    esac
    AC_DEFINE_UNQUOTED([COAP_MAX_LOGGING_LEVEL], [$enable_max_logging_level], [Define to level if max logging level is not 8])
fi

# Checks for typedefs, structures, and compiler characteristics.
AC_TYPE_SIZE_T
AC_TYPE_SSIZE_T

# Checks for library functions.
AC_CHECK_FUNCS([memset select socket strcasecmp strrchr getaddrinfo \
                strnlen malloc pthread_mutex_lock getrandom random if_nametoindex])

# Check if -lsocket -lnsl is required (specifically Solaris)
AC_SEARCH_LIBS([socket], [socket])
AC_SEARCH_LIBS([inet_ntop], [nsl])

# Check if clock_gettime() requires librt, when available
AC_SEARCH_LIBS([clock_gettime], [rt])

#check for struct cmsghdr
AC_CHECK_TYPES([struct cmsghdr],,,[
AC_INCLUDES_DEFAULT
#include <sys/socket.h>])

AC_MSG_CHECKING([operating system])

# Set up here some extra platform depended defines and variables.
# The "ADDITIONAL_CFLAGS" is need as this stand-alone definition
# for the doxygen part.
case $host in
    *-linux* | *-uclinux*)
    AC_MSG_RESULT([Linux])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE"

    # Not yet needed but if some code definitions have to depend on the platform.
    #AC_DEFINE(OS_LINUX, 1, [Linux backend])
    #AC_SUBST(OS_LINUX)
    ;;

    *-cygwin*)
    AC_MSG_RESULT([Cygwin])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE -D_CYGWIN_ENV"
    LDFLAGS="-no-undefined $LDFLAGS"
    ;;

    *-solaris*)
    AC_MSG_RESULT([Solaris])
    # set _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED to enable XPG4v2 (POSIX 2004)
    # set __EXTENSION__ to shut up feature test macros that restrict -std=c99
    # to only C99 (and nothing newer)
    ADDITIONAL_CFLAGS="-D_XOPEN_SOURCE=600 -D_XOPEN_SOURCE_EXTENDED=600 -D__EXTENSIONS__=1"
    ;;

    *-darwin*)
    AC_MSG_RESULT([Darwin])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE"

    AC_DEFINE(__APPLE_USE_RFC_3542, 1, [Define this to 1 for ancillary data on MacOS])

    # Not yet needed but if some code definitions have to depend on the platform.
    #AC_DEFINE(OS_MACOS, 1, [MacOS backend])
    #AC_SUBST(OS_MACOS)
    ;;

    *-freebsd1*)
    AC_MSG_RESULT([FreeBSD-1x])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE"
    ;;

    *kfreebsd*)
    AC_MSG_RESULT([kFreeBSD])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE"
    ;;

    *mingw*)
    AC_MSG_RESULT([MinGW])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE -Wno-format -Wno-format-security"
    LIBS="${LIBS} -lws2_32"
    ;;

    *-qnx*)
    AC_MSG_RESULT([QNX])
    ADDITIONAL_CFLAGS="-D_QNX_SOURCE"
    ;;

    *xtensa-esp32-elf*)
    AC_MSG_RESULT([XtensaEsp32Elf])
    ADDITIONAL_CFLAGS="-D_GNU_SOURCE -DWITH_POSIX"
    ;;

    *)
    AC_MSG_WARN([==> Currently unsupported operating system '${host}' !])
    AC_MSG_ERROR([==> If you can provide patches to support your operating system please raise a Pull Request at 'https://github.com/obgm/libcoap/pulls'.])
esac

# Exporting the PREDEFINED_CFLAGS definition
PREDEFINED_CFLAGS=`echo $ADDITIONAL_CFLAGS | $SED -e 's/-D//g'`
AC_SUBST(PREDEFINED_CFLAGS)

# And finally combining the CFLAGS together ...
CFLAGS="$CFLAGS $ADDITIONAL_CFLAGS"

# Override the various template files, currently just makefiles and the
# pkgconfig *.pc file.
# Later if the API version is changing don't forget to change the
# libcoap-$LIBCOAP_API_VERSION.pc.in file too!! You will have to change
# the 'Cflags' variable to something like
#     Cflags: -I${includedir}/coap-@LIBCOAP_API_VERSION@
#
AC_CONFIG_FILES([
Makefile
doc/Makefile
examples/Makefile
man/coap.txt
man/coap_address.txt
man/coap_async.txt
man/coap_attribute.txt
man/coap_block.txt
man/coap_cache.txt
man/coap_context.txt
man/coap_deprecated.txt
man/coap_encryption.txt
man/coap_endpoint_client.txt
man/coap_endpoint_server.txt
man/coap_handler.txt
man/coap_init.txt
man/coap_io.txt
man/coap_keepalive.txt
man/coap_locking.txt
man/coap_logging.txt
man/coap_lwip.txt
man/coap_observe.txt
man/coap_oscore.txt
man/coap_pdu_access.txt
man/coap_pdu_setup.txt
man/coap_persist.txt
man/coap_proxy.txt
man/coap_recovery.txt
man/coap_resource.txt
man/coap_session.txt
man/coap_string.txt
man/coap_supported.txt
man/coap_tls_library.txt
man/coap_uri.txt
man/coap_websockets.txt
man/coap-client.txt
man/coap-oscore-conf.txt
man/coap-server.txt
man/coap-rd.txt
man/coap-tls-engine-conf.txt
man/Makefile
scripts/fix_version.sh
tests/test_common.h
tests/Makefile
tests/oss-fuzz/Makefile.ci
libcoap-$LIBCOAP_NAME_SUFFIX.pc:libcoap-$LIBCOAP_API_VERSION.pc.in
])

AC_OUTPUT

LIBCOAP_BUILD=`git describe --tags --dirty --always`
if test "x$LIBCOAP_BUILD" = "x"; then
    LIBCOAP_BUILD=$PACKAGE_VERSION
fi

AC_MSG_RESULT([
libcoap Configuration Summary:
      libcoap package version        : "$PACKAGE_VERSION"
      libcoap package source         : "$LIBCOAP_BUILD"
      libcoap API version            : "$LIBCOAP_API_VERSION"
      libcoap ABI version            : "$LIBCOAP_ABI_VERSION"
      libcoap libtool SO version     : "$LIBCOAP_SO_VERSION"
      libcoap DTLS lib extn          : "$LIBCOAP_DTLS_LIB_EXTENSION_NAME"
      host system                    : "$host"]);
if test "x$enable_server_mode" = "xyes"; then
    AC_MSG_RESULT([      build with server support      : "yes"])
else
    AC_MSG_RESULT([      build with server support      : "no"])
fi
if test "x$enable_client_mode" = "xyes"; then
    AC_MSG_RESULT([      build with client support      : "yes"])
else
    AC_MSG_RESULT([      build with client support      : "no"])
fi
if test "x$enable_client_mode" = "xyes"; then
    AC_MSG_RESULT([      build with proxy support       : "yes"])
else
    AC_MSG_RESULT([      build with proxy support       : "no"])
fi
if test "x$build_ipv4" != "xno"; then
    AC_MSG_RESULT([      build with IPv4 support        : "yes"])
else
    AC_MSG_RESULT([      build with IPv4 support        : "no"])
fi
if test "x$build_ipv6" != "xno"; then
    AC_MSG_RESULT([      build with IPv6 support        : "yes"])
else
    AC_MSG_RESULT([      build with IPv6 support        : "no"])
fi
if test "x$build_af_unix" != "xno"; then
    AC_MSG_RESULT([      build with Unix socket support : "yes"])
else
    AC_MSG_RESULT([      build with Unix socket support : "no"])
fi
if test "x$build_tcp" != "xno"; then
    AC_MSG_RESULT([      build with TCP support         : "yes"])
else
    AC_MSG_RESULT([      build with TCP support         : "no"])
fi
if test "x$with_gnutls" = "xyes" -o "x$with_gnutls_auto" = "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "yes"])
    AC_MSG_RESULT([          -->  GnuTLS around         : "yes" (found GnuTLS $gnutls_version)])
    AC_MSG_RESULT([               GnuTLS_CFLAGS         : "$GnuTLS_CFLAGS"])
    AC_MSG_RESULT([               GnuTLS_LIBS           : "$GnuTLS_LIBS"])
fi
if test "x$with_openssl" = "xyes" -o "x$with_openssl_auto" = "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "yes"])
    AC_MSG_RESULT([         -->  OpenSSL around         : "yes" (found OpenSSL $openssl_version)])
    AC_MSG_RESULT([              OpenSSL_CFLAGS         : "$OpenSSL_CFLAGS"])
    AC_MSG_RESULT([              OpenSSL_LIBS           : "$OpenSSL_LIBS"])
fi
if test "x$with_wolfssl" = "xyes" -o "x$with_wolfssl_auto" = "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "yes"])
    AC_MSG_RESULT([         -->  wolfSSL around         : "yes" (found wolfSSL $wolfssl_version)])
    AC_MSG_RESULT([              wolfSSL_CFLAGS         : "$wolfSSL_CFLAGS"])
    AC_MSG_RESULT([              wolfSSL_LIBS           : "$wolfSSL_LIBS"])
fi
if test "x$with_mbedtls" = "xyes" -o "x$with_mbedtls_auto" = "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "yes"])
    if test "x$mbedtls_has_pkgconfig" = "xyes"; then
      AC_MSG_RESULT([         -->  Mbed TLS around        : "yes" (found Mbed TLS $mbedtls_version using pkg-config)])
    else
      AC_MSG_RESULT([         -->  Mbed TLS around        : "yes" (found Mbed TLS $mbedtls_version without pkg-config)])
    fi
    AC_MSG_RESULT([              MbedTLS_CFLAGS         : "$MbedTLS_CFLAGS"])
    AC_MSG_RESULT([              MbedTLS_LIBS           : "$MbedTLS_LIBS"])
fi
if test "x$with_tinydtls" = "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "yes"])
    if test "x$have_submodule_tinydtls" = "xyes"; then
        AC_MSG_RESULT([         -->  TinyDTLS around        : "yes" (submodule)])
    else
        AC_MSG_RESULT([         -->  TinyDTLS around        : "yes (found TinyDTLS $tinydtls_version)"])
    fi
    AC_MSG_RESULT([              TinyDTLS_CFLAGS        : "$DTLS_CFLAGS"])
    AC_MSG_RESULT([              TinyDTLS_LIBS          : "$DTLS_LIBS"])
fi
if test "x$build_dtls" != "xyes"; then
    AC_MSG_RESULT([      build DTLS support             : "no"])
fi
if test "x$build_add_default_names" = "xyes"; then
    AC_MSG_RESULT([      add default names              : "yes"])
else
    AC_MSG_RESULT([      add default names              : "no"])
fi
if test "x$build_observe_persist" = "xyes"; then
    AC_MSG_RESULT([      build Observe Persist          : "yes"])
else
    AC_MSG_RESULT([      build Observe Persist          : "no"])
fi
if test "x$have_epoll" = "xyes"; then
    AC_MSG_RESULT([      build using epoll              : "$with_epoll"])
fi
AC_MSG_RESULT([      enable small stack size        : "$enable_small_stack"])
if test "x$build_async" != "xno"; then
    AC_MSG_RESULT([      enable separate responses      : "yes"])
else
    AC_MSG_RESULT([      enable separate responses      : "no"])
fi
if test "x$build_oscore" != "xno"; then
    AC_MSG_RESULT([      enable OSCORE support          : "yes"])
else
    AC_MSG_RESULT([      enable OSCORE support          : "no"])
fi
if test "x$build_q_block" != "xno"; then
    AC_MSG_RESULT([      enable Q-Block support         : "yes"])
else
    AC_MSG_RESULT([      enable Q-Block support         : "no"])
fi
if test "x$enable_max_logging_level" != "x8"; then
    AC_MSG_RESULT([      enable max logging level       : "$enable_max_logging_level"])
else
    AC_MSG_RESULT([      enable max logging level       : "none"])
fi
AC_MSG_RESULT([      enable thread safe code        : "$enable_thread_safe"])
AC_MSG_RESULT([      enable recursive lock check    : "$enable_recursive_detection"])
if test "x$build_doxygen" = "xyes"; then
    AC_MSG_RESULT([      build doxygen pages            : "yes"])
    AC_MSG_RESULT([          --> Doxygen around         : "yes" ($DOXYGEN $doxygen_version)])
    if test "x$DOT" = "x"; then
        AC_MSG_RESULT([             -->  dot around         : "no" (DOT not found!)])
    else
        AC_MSG_RESULT([             -->  dot around         : "yes" ($DOT $dot_version)])
    fi
else
    if test "x$build_doxygen" = "xno"; then
        AC_MSG_RESULT([      build doxygen pages            : "no"])
    fi
fi
if test "x$build_manpages" = "xyes"; then
    AC_MSG_RESULT([      build man pages                : "yes"])
else
    AC_MSG_RESULT([      build man pages                : "no"])
fi
if test "x$build_tests" = "xyes"; then
    AC_MSG_RESULT([      build unit test binary         : "yes"])
else
    AC_MSG_RESULT([      build unit test binary         : "no"])
fi
if test "x$build_examples" = "xyes"; then
    AC_MSG_RESULT([      build examples                 : "yes"])
else
    AC_MSG_RESULT([      build examples                 : "no"])
fi
if test "x$build_examples_source" = "xyes"; then
    AC_MSG_RESULT([      install examples source        : "yes"])
else
    AC_MSG_RESULT([      install examples source        : "no"])
fi
if test "x$build_gcov" = "xyes"; then
    AC_MSG_RESULT([      build with gcov support        : "yes"])
else
    AC_MSG_RESULT([      build with gcov support        : "no"])
fi
if test "x$enable_shared" = "xyes"; then
    AC_MSG_RESULT([      build shared library           : "yes"])
else
    AC_MSG_RESULT([      build shared library           : "no"])
fi
if test "x$enable_static" = "xyes"; then
    AC_MSG_RESULT([      build static library           : "yes"])
else
    AC_MSG_RESULT([      build static library           : "no"])
fi

mkdir -p include/coap$LIBCOAP_API_VERSION
LT_TEMP=`grep -B2 " COAP_" coap_config.h > include/coap$LIBCOAP_API_VERSION/coap_defines.h`
if test "x$LT_TEMP" != "x" ; then
    AC_MSG_ERROR([Unable to build coap_defines.h])
fi