configure.ac

dnl Copyright (c) 2001-2004, Roger Dingledine
dnl Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson
dnl Copyright (c) 2007-2019, The Tor Project, Inc.
dnl See LICENSE for licensing information

AC_PREREQ([2.63])
AC_INIT([tor],[0.4.5.7])
AC_CONFIG_SRCDIR([src/app/main/tor_main.c])
AC_CONFIG_MACRO_DIR([m4])

configure_flags="$*"

# DO NOT EDIT THIS DEFINITION BY HAND UNLESS YOU KNOW WHAT YOU'RE DOING.
#
# The update_versions.py script updates this definition when the
# version number changes.  Tor uses it to make sure that it
# only shuts down for missing "required protocols" when those protocols
# are listed as required by a consensus after this date.
AC_DEFINE(APPROX_RELEASE_DATE, ["2021-03-15"], # for 0.4.5.7
          [Approximate date when this software was released. (Updated when the version changes.)])

# "foreign" means we don't follow GNU package layout standards
# "1.11" means we require automake version 1.11 or newer
# "subdir-objects" means put .o files in the same directory as the .c files
AM_INIT_AUTOMAKE([foreign 1.11 subdir-objects -Wall -Werror])

tor_ac_n_warnings=0
tor_incr_n_warnings() {
  tor_ac_n_warnings=`expr $tor_ac_n_warnings + 1`
}

m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
AC_CONFIG_HEADERS([orconfig.h])

AC_USE_SYSTEM_EXTENSIONS
AC_CANONICAL_HOST

PKG_PROG_PKG_CONFIG
if test "x$PKG_CONFIG" = "x" ; then
    pkg_config_user_action="install pkg-config, and check the PKG_CONFIG_PATH environment variable"
    AC_MSG_NOTICE([Some libraries need pkg-config, including systemd, nss, lzma, zstd, and custom mallocs.])
    AC_MSG_NOTICE([To use those libraries, $pkg_config_user_action.])
else
    pkg_config_user_action="check the PKG_CONFIG_PATH environment variable"
fi

if test "x$PKG_CONFIG_PATH" = "x" && test "x$prefix" != "xNONE" && test "$host" != "$build"; then
   export PKG_CONFIG_PATH=$prefix/lib/pkgconfig
   AC_MSG_NOTICE([set PKG_CONFIG_PATH=$PKG_CONFIG_PATH to support cross-compiling])
fi

AC_ARG_ENABLE(openbsd-malloc,
   AS_HELP_STRING(--enable-openbsd-malloc, [use malloc code from OpenBSD.  Linux only. Deprecated: see --with-malloc]))
AC_ARG_ENABLE(static-openssl,
   AS_HELP_STRING(--enable-static-openssl, [link against a static openssl library. Requires --with-openssl-dir]))
AC_ARG_ENABLE(static-libevent,
   AS_HELP_STRING(--enable-static-libevent, [link against a static libevent library. Requires --with-libevent-dir]))
AC_ARG_ENABLE(static-zlib,
   AS_HELP_STRING(--enable-static-zlib, [link against a static zlib library. Requires --with-zlib-dir]))
AC_ARG_ENABLE(static-tor,
   AS_HELP_STRING(--enable-static-tor, [create an entirely static Tor binary. Requires --with-openssl-dir and --with-libevent-dir and --with-zlib-dir]))
AC_ARG_ENABLE(unittests,
   AS_HELP_STRING(--disable-unittests, [don't build unit tests for Tor. Risky!]))
AC_ARG_ENABLE(coverage,
   AS_HELP_STRING(--enable-coverage, [enable coverage support in the unit-test build]))
AC_ARG_ENABLE(asserts-in-tests,
   AS_HELP_STRING(--disable-asserts-in-tests, [disable tor_assert() calls in the unit tests, for branch coverage]))
AC_ARG_ENABLE(system-torrc,
   AS_HELP_STRING(--disable-system-torrc, [don't look for a system-wide torrc file]))
AC_ARG_ENABLE(libfuzzer,
   AS_HELP_STRING(--enable-libfuzzer, [build extra fuzzers based on 'libfuzzer']))
AC_ARG_ENABLE(oss-fuzz,
   AS_HELP_STRING(--enable-oss-fuzz, [build extra fuzzers based on 'oss-fuzz' environment]))
AC_ARG_ENABLE(memory-sentinels,
   AS_HELP_STRING(--disable-memory-sentinels, [disable code that tries to prevent some kinds of memory access bugs. For fuzzing only.]))
AC_ARG_ENABLE(rust,
   AS_HELP_STRING(--enable-rust, [enable rust integration]))
AC_ARG_ENABLE(cargo-online-mode,
   AS_HELP_STRING(--enable-cargo-online-mode, [Allow cargo to make network requests to fetch crates. For builds with rust only.]))
AC_ARG_ENABLE(restart-debugging,
   AS_HELP_STRING(--enable-restart-debugging, [Build Tor with support for debugging in-process restart. Developers only.]))
AC_ARG_ENABLE(zstd-advanced-apis,
   AS_HELP_STRING(--disable-zstd-advanced-apis, [Build without support for zstd's "static-only" APIs.]))
AC_ARG_ENABLE(nss,
   AS_HELP_STRING(--enable-nss, [Use Mozilla's NSS TLS library. (EXPERIMENTAL)]))
AC_ARG_ENABLE(pic,
   AS_HELP_STRING(--enable-pic, [Build Tor's binaries as position-independent code, suitable to link as a library.]))

AC_ARG_ENABLE(missing-doc-warnings,
   AS_HELP_STRING(--enable-missing-doc-warnings, [Tell doxygen to warn about missing documentation. Makes doxygen warnings nonfatal.]))

if test "$enable_missing_doc_warnings" = "yes"; then
   DOXYGEN_FATAL_WARNINGS=NO
   DOXYGEN_WARN_ON_MISSING=YES
elif test "$enable_fatal_warnings" = "yes"; then
   # Fatal warnings from doxygen are nice, but not if we're warning about
   # missing documentation.
   DOXYGEN_FATAL_WARNINGS=YES
   DOXYGEN_WARN_ON_MISSING=NO
else
   DOXYGEN_FATAL_WARNINGS=NO
   DOXYGEN_WARN_ON_MISSING=NO
fi
AC_SUBST(DOXYGEN_FATAL_WARNINGS)
AC_SUBST(DOXYGEN_WARN_ON_MISSING)

if test "x$enable_coverage" != "xyes" -a "x$enable_asserts_in_tests" = "xno" ; then
    AC_MSG_ERROR([Can't disable assertions outside of coverage build])
fi

AM_CONDITIONAL(UNITTESTS_ENABLED, test "x$enable_unittests" != "xno")
AM_CONDITIONAL(COVERAGE_ENABLED, test "x$enable_coverage" = "xyes")
AM_CONDITIONAL(DISABLE_ASSERTS_IN_UNIT_TESTS, test "x$enable_asserts_in_tests" = "xno")
AM_CONDITIONAL(LIBFUZZER_ENABLED, test "x$enable_libfuzzer" = "xyes")
AM_CONDITIONAL(OSS_FUZZ_ENABLED, test "x$enable_oss_fuzz" = "xyes")
AM_CONDITIONAL(USE_RUST, test "x$enable_rust" = "xyes")
AM_CONDITIONAL(USE_NSS, test "x$enable_nss" = "xyes")
AM_CONDITIONAL(USE_OPENSSL, test "x$enable_nss" != "xyes")

if test "x$enable_nss" = "xyes"; then
  AC_DEFINE(ENABLE_NSS, 1,
  	    [Defined if we're building with NSS.])
else
  AC_DEFINE(ENABLE_OPENSSL, 1,
            [Defined if we're building with OpenSSL or LibreSSL])
fi

if test "$enable_static_tor" = "yes"; then
  enable_static_libevent="yes";
  enable_static_openssl="yes";
  enable_static_zlib="yes";
  TOR_STATIC_LDFLAGS="-static"
fi
AC_SUBST(TOR_STATIC_LDFLAGS)

if test "$enable_system_torrc" = "no"; then
  AC_DEFINE(DISABLE_SYSTEM_TORRC, 1,
            [Defined if we're not going to look for a torrc in SYSCONF])
fi

if test "$enable_memory_sentinels" = "no"; then
  AC_DEFINE(DISABLE_MEMORY_SENTINELS, 1,
           [Defined if we're turning off memory safety code to look for bugs])
fi

AC_ARG_ENABLE(manpage,
              AS_HELP_STRING(--disable-manpage, [Disable manpage generation.]))

AC_ARG_ENABLE(html-manual,
              AS_HELP_STRING(--disable-html-manual, [Disable HTML documentation.]))

AC_ARG_ENABLE(asciidoc,
     AS_HELP_STRING(--disable-asciidoc, [don't use asciidoc (disables building of manpages)]),
     [case "${enableval}" in
        "yes") asciidoc=true ;;
        "no")  asciidoc=false ;;
        *) AC_MSG_ERROR(bad value for --disable-asciidoc) ;;
      esac], [asciidoc=true])

# systemd notify support
AC_ARG_ENABLE(systemd,
      AS_HELP_STRING(--enable-systemd, [enable systemd notification support]),
      [case "${enableval}" in
        "yes") systemd=true ;;
        "no")  systemd=false ;;
        * ) AC_MSG_ERROR(bad value for --enable-systemd) ;;
      esac], [systemd=auto])

if test "$enable_restart_debugging" = "yes"; then
  AC_DEFINE(ENABLE_RESTART_DEBUGGING, 1,
            [Defined if we're building with support for in-process restart debugging.])
fi

if test "$enable_zstd_advanced_apis" != "no"; then
   AC_DEFINE(ENABLE_ZSTD_ADVANCED_APIS, 1,
             [Defined if we're going to try to use zstd's "static-only" APIs.])
fi

# systemd support
if test "x$enable_systemd" = "xno"; then
    have_systemd=no;
else
    PKG_CHECK_MODULES(SYSTEMD,
        [libsystemd-daemon],
        have_systemd=yes,
        have_systemd=no)
    if test "x$have_systemd" = "xno"; then
        AC_MSG_NOTICE([Okay, checking for systemd a different way...])
        PKG_CHECK_MODULES(SYSTEMD,
            [libsystemd],
            have_systemd=yes,
            have_systemd=no)
    fi
fi

if test "x$have_systemd" = "xyes"; then
    AC_DEFINE(HAVE_SYSTEMD,1,[Have systemd])
    TOR_SYSTEMD_CFLAGS="${SYSTEMD_CFLAGS}"
    TOR_SYSTEMD_LIBS="${SYSTEMD_LIBS}"
    PKG_CHECK_MODULES(LIBSYSTEMD209, [libsystemd >= 209],
         [AC_DEFINE(HAVE_SYSTEMD_209,1,[Have systemd v209 or greater])], [])
fi
AC_SUBST(TOR_SYSTEMD_CFLAGS)
AC_SUBST(TOR_SYSTEMD_LIBS)

if test "x$enable_systemd" = "xyes" -a "x$have_systemd" != "xyes" ; then
    AC_MSG_ERROR([Explicitly requested systemd support, but systemd not found, $pkg_config_user_action, or set SYSTEMD_CFLAGS and SYSTEMD_LIBS.])
fi

case "$host" in
   *-*-solaris* )
     AC_DEFINE(_REENTRANT, 1, [Define on some platforms to activate x_r() functions in time.h])
     ;;
esac

AC_ARG_ENABLE(gcc-warnings,
     AS_HELP_STRING(--enable-gcc-warnings, [deprecated alias for enable-fatal-warnings]))
AC_ARG_ENABLE(fatal-warnings,
     AS_HELP_STRING(--enable-fatal-warnings, [tell the compiler to treat all warnings as errors.]))
AC_ARG_ENABLE(gcc-warnings-advisory,
     AS_HELP_STRING(--disable-gcc-warnings-advisory, [disable the regular verbose warnings]))

dnl Others suggest '/gs /safeseh /nxcompat /dynamicbase' for non-gcc on Windows
AC_ARG_ENABLE(gcc-hardening,
    AS_HELP_STRING(--disable-gcc-hardening, [disable compiler security checks]))

dnl Deprecated --enable-expensive-hardening but keep it for now for backward compat.
AC_ARG_ENABLE(expensive-hardening,
    AS_HELP_STRING(--enable-expensive-hardening, [enable more fragile and expensive compiler hardening; makes Tor slower]))
AC_ARG_ENABLE(fragile-hardening,
    AS_HELP_STRING(--enable-fragile-hardening, [enable more fragile and expensive compiler hardening; makes Tor slower]))
if test "x$enable_expensive_hardening" = "xyes" || test "x$enable_fragile_hardening" = "xyes"; then
  fragile_hardening="yes"
  AC_DEFINE(DEBUG_SMARTLIST, 1, [Enable smartlist debugging])
fi

AC_ARG_ENABLE(all-bugs-are-fatal,
   AS_HELP_STRING(--enable-all-bugs-are-fatal, [force all soft asserts in Tor codebase (tor_assert_nonfatal(), BUG(), etc.) to act as hard asserts (tor_assert() and equivalents); makes Tor fragile; only recommended for dev builds]))

if test "x$enable_all_bugs_are_fatal" = "xyes"; then
  AC_DEFINE(ALL_BUGS_ARE_FATAL, 1, [All assert failures are fatal])
fi

dnl Linker hardening options
dnl Currently these options are ELF specific - you can't use this with MacOSX
AC_ARG_ENABLE(linker-hardening,
    AS_HELP_STRING(--disable-linker-hardening, [disable linker security fixups]))

AC_ARG_ENABLE(local-appdata,
   AS_HELP_STRING(--enable-local-appdata, [default to host local application data paths on Windows]))
if test "$enable_local_appdata" = "yes"; then
  AC_DEFINE(ENABLE_LOCAL_APPDATA, 1,
            [Defined if we default to host local appdata paths on Windows])
fi

AC_ARG_ENABLE(tool-name-check,
     AS_HELP_STRING(--disable-tool-name-check, [check for sanely named toolchain when cross-compiling]))

AC_ARG_ENABLE(seccomp,
     AS_HELP_STRING(--disable-seccomp, [do not attempt to use libseccomp]))

AC_ARG_ENABLE(libscrypt,
     AS_HELP_STRING(--disable-libscrypt, [do not attempt to use libscrypt]))

dnl --- Tracing Options. ---

TOR_TRACE_LIBS=

dnl LTTng instrumentation option.
AC_ARG_ENABLE(tracing-instrumentation-lttng,
              AS_HELP_STRING([--enable-tracing-instrumentation-lttng],
                             [build with LTTng-UST instrumentation]))
AM_CONDITIONAL([USE_TRACING_INSTRUMENTATION_LTTNG],
               [test "x$enable_tracing_instrumentation_lttng" = "xyes"])

if test "x$enable_tracing_instrumentation_lttng" = "xyes"; then
  AC_CHECK_HEADERS([lttng/tracepoint.h], [],
                   [AC_MSG_ERROR([LTTng instrumentation headers not found.
                                  On Debian, apt install liblttng-ust-dev"])], [])
  AC_DEFINE([USE_TRACING_INSTRUMENTATION_LTTNG], [1], [Using LTTng instrumentation])
  TOR_TRACE_LIBS="-llttng-ust -ldl"
  have_tracing=1
fi

dnl USDT instrumentation option.
AC_ARG_ENABLE(tracing-instrumentation-usdt,
              AS_HELP_STRING([--enable-tracing-instrumentation-usdt],
                             [build with tracing USDT instrumentation]))
AM_CONDITIONAL([USE_TRACING_INSTRUMENTATION_USDT],
               [test "x$enable_tracing_instrumentation_usdt" = "xyes"])

if test "x$enable_tracing_instrumentation_usdt" = "xyes"; then
  AC_CHECK_HEADERS([sys/sdt.h], [],
                   [AC_MSG_ERROR([USDT instrumentation requires sys/sdt.h header.
                                  On Debian, apt install systemtap-sdt-dev])], [])
  AC_MSG_CHECKING([STAP_PROBEV()])
  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
    #define SDT_USE_VARIADIC
    #include <sys/sdt.h>
    void test(void)
    {
      STAP_PROBEV(p, n, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
    }
  ]])], [
    AC_MSG_RESULT([yes])
    dnl LTTng generates USDT probes if the UST library was built with
    dnl --with-sdt. There is unfortunately no way to check that so we always
    dnl build the USDT probes even though LTTng instrumentation was requested.
    AC_DEFINE([USE_TRACING_INSTRUMENTATION_USDT], [1], [Using USDT instrumentation])
    have_tracing=1
  ], [
    AC_MSG_RESULT([no])
    AC_MSG_ERROR([USDT tracing support requires STAP_PROBEV()])
  ])
fi

dnl Tracepoints event to debug logs.
AC_ARG_ENABLE(tracing-instrumentation-log-debug,
     AS_HELP_STRING([--enable-tracing-instrumentation-log-debug],
                    [build with tracing event to debug log]),
     AC_DEFINE([USE_TRACING_INSTRUMENTATION_LOG_DEBUG], [1],
               [Tracepoints to log debug]), [])
AM_CONDITIONAL([USE_TRACING_INSTRUMENTATION_LOG_DEBUG],
               [test "x$enable_tracing_instrumentation_log_debug" = "xyes"])
if test "x$enable_tracing_instrumentation_log_debug" = "xyes"; then
  have_tracing=1
fi

dnl Define that tracing is supported if any instrumentation is used.
AM_COND_IF([USE_TRACING_INSTRUMENTATION_LOG_DEBUG],
           AC_DEFINE([HAVE_TRACING], [1], [Compiled with tracing support]))
AM_COND_IF([USE_TRACING_INSTRUMENTATION_USDT],
           AC_DEFINE([HAVE_TRACING], [1], [Compiled with tracing support]))
AM_COND_IF([USE_TRACING_INSTRUMENTATION_LTTNG],
           AC_DEFINE([HAVE_TRACING], [1], [Compiled with tracing support]))
AM_CONDITIONAL([USE_TRACING], [test "x$have_tracing" = x1 ])

dnl Finally, define the trace libs.
AC_SUBST([TOR_TRACE_LIBS])

dnl -- End Tracing Options. --

dnl Enable Android only features.
AC_ARG_ENABLE(android,
     AS_HELP_STRING(--enable-android, [build with Android features enabled]))
AM_CONDITIONAL([USE_ANDROID], [test "x$enable_android" = "xyes"])

if test "x$enable_android" = "xyes"; then
  AC_DEFINE([USE_ANDROID], [1], [Compile with Android specific features enabled])

fi

dnl ---
dnl Tor modules options. These options are namespaced with --disable-module-XXX
dnl ---

dnl All our modules.
m4_define(MODULES, relay dirauth dircache)

# Some modules are only disabled through another option. For those, we don't
# want to print the help in the summary at the end of the configure. Any entry
# in the following set will not print the "--disable-module-NAME" command in
# the summary.
m4_set_add_all([MODULES_WITH_NO_OPTIONS], [dircache])

dnl Relay module.
AC_ARG_ENABLE([module-relay],
              AS_HELP_STRING([--disable-module-relay],
                             [Build tor without the Relay modules: tor can not run as a relay, bridge, or authority. Implies --disable-module-dirauth]))
AM_CONDITIONAL(BUILD_MODULE_RELAY, [test "x$enable_module_relay" != "xno"])
AM_COND_IF(BUILD_MODULE_RELAY,
           AC_DEFINE([HAVE_MODULE_RELAY], [1],
                     [Compile with Relay feature support]))

dnl Dircache module.  (This cannot be enabled or disabled independently of
dnl the relay module.  It is not listed by --list-modules for this reason.)
AM_CONDITIONAL(BUILD_MODULE_DIRCACHE,
               [test "x$enable_module_relay" != "xno"])
AM_COND_IF(BUILD_MODULE_DIRCACHE,
           AC_DEFINE([HAVE_MODULE_DIRCACHE], [1],
                     [Compile with directory cache support]))

dnl Directory Authority module.
AC_ARG_ENABLE([module-dirauth],
              AS_HELP_STRING([--disable-module-dirauth],
                             [Build tor without the Directory Authority module: tor can not run as a directory authority or bridge authority]))
AM_CONDITIONAL(BUILD_MODULE_DIRAUTH,[test "x$enable_module_dirauth" != "xno" && test "x$enable_module_relay" != "xno"])
AM_COND_IF(BUILD_MODULE_DIRAUTH,
           AC_DEFINE([HAVE_MODULE_DIRAUTH], [1],
                     [Compile with Directory Authority feature support]))

dnl Helper variables.
TOR_MODULES_ALL_ENABLED=
AC_DEFUN([ADD_MODULE], [
    MODULE=m4_toupper($1)
    TOR_MODULES_ALL_ENABLED="${TOR_MODULES_ALL_ENABLED} -DHAVE_MODULE_${MODULE}=1"
])
m4_foreach_w([module], MODULES, [ADD_MODULE([module])])
AC_SUBST(TOR_MODULES_ALL_ENABLED)

dnl check for the correct "ar" when cross-compiling.
dnl   (AM_PROG_AR was new in automake 1.11.2, which we do not yet require,
dnl    so kludge up a replacement for the case where it isn't there yet.)
m4_ifdef([AM_PROG_AR],
         [AM_PROG_AR],
         [AN_MAKEVAR([AR], [AC_PROG_AR])
          AN_PROGRAM([ar], [AC_PROG_AR])
          AC_DEFUN([AC_PROG_AR], [AC_CHECK_TOOL([AR], [ar], [:])])
          AC_PROG_AR])

dnl Check whether the above macro has settled for a simply named tool even
dnl though we're cross compiling. We must do this before running AC_PROG_CC,
dnl because that will find any cc on the system, not only the cross-compiler,
dnl and then verify that a binary built with this compiler runs on the
dnl build system. It will then come to the false conclusion that we're not
dnl cross-compiling.
if test "x$enable_tool_name_check" != "xno"; then
    if test "x$ac_tool_warned" = "xyes"; then
        AC_MSG_ERROR([We are cross compiling but could not find a properly named toolchain. Do you have your cross-compiling toolchain in PATH? (You can --disable-tool-name-check to ignore this.)])
	elif test "x$ac_ct_AR" != "x" -a "x$cross_compiling" = "xmaybe"; then
		AC_MSG_ERROR([We think we are cross compiling but could not find a properly named toolchain. Do you have your cross-compiling toolchain in PATH? (You can --disable-tool-name-check to ignore this.)])
	fi
fi

AC_PROG_CC
AC_PROG_CPP
AC_PROG_MAKE_SET
AC_PROG_RANLIB
AC_PROG_SED

AC_ARG_VAR([PERL], [path to Perl binary])
AC_CHECK_PROGS([PERL], [perl])
AM_CONDITIONAL(USE_PERL, [test "x$ac_cv_prog_PERL" != "x"])

dnl check for asciidoc and a2x
AC_PATH_PROG([ASCIIDOC], [asciidoc], none)
AC_PATH_PROGS([A2X], [a2x a2x.py], none)

AM_CONDITIONAL(USE_ASCIIDOC, test "x$asciidoc" = "xtrue")
AM_CONDITIONAL(BUILD_MANPAGE, [test "x$enable_manpage" != "xno"])
AM_CONDITIONAL(BUILD_HTML_DOCS, [test "x$enable_html_manual" != "xno"])

AM_PROG_CC_C_O
AC_PROG_CC_C99

AC_CACHE_CHECK([for Python 3], [tor_cv_PYTHON],
   [AC_PATH_PROGS_FEATURE_CHECK([PYTHON], [ \
	python3 \
	python3.8 python3.7 python3.6 python3.5 python3.4 \
	python ],
   [["$ac_path_PYTHON" -c 'import sys; sys.exit(sys.version_info[0]<3)' && tor_cv_PYTHON="$ac_path_PYTHON" ac_path_PYTHON_found=:]] )])
AC_SUBST([PYTHON], [$tor_cv_PYTHON])

PYTHON="$tor_cv_PYTHON"

if test "x$PYTHON" = "x"; then
  tor_incr_n_warnings
  AC_MSG_WARN([Python 3 unavailable; some tests will not be run.])
fi

AM_CONDITIONAL(USEPYTHON, [test "x$PYTHON" != "x"])

dnl List all external rust crates we depend on here. Include the version
rust_crates=" \
    digest-0.7.2 \
    libc-0.2.39 \
"
AC_SUBST(rust_crates)

ifdef([AC_C_FLEXIBLE_ARRAY_MEMBER], [
AC_C_FLEXIBLE_ARRAY_MEMBER
], [
 dnl Maybe we've got an old autoconf...
 AC_CACHE_CHECK([for flexible array members],
     tor_cv_c_flexarray,
     [AC_COMPILE_IFELSE(
       AC_LANG_PROGRAM([
 struct abc { int a; char b[]; };
], [
 struct abc *def = malloc(sizeof(struct abc)+sizeof(char));
 def->b[0] = 33;
]),
  [tor_cv_c_flexarray=yes],
  [tor_cv_c_flexarray=no])])
 if test "$tor_cv_flexarray" = "yes"; then
   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [], [Define to nothing if C supports flexible array members, and to 1 if it does not.])
 else
   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1], [Define to nothing if C supports flexible array members, and to 1 if it does not.])
 fi
])

AC_CACHE_CHECK([for working C99 mid-block declaration syntax],
      tor_cv_c_c99_decl,
      [AC_COMPILE_IFELSE(
         [AC_LANG_PROGRAM([], [int x; x = 3; int y; y = 4 + x;])],
	 [tor_cv_c_c99_decl=yes],
	 [tor_cv_c_c99_decl=no] )])
if test "$tor_cv_c_c99_decl" != "yes"; then
  AC_MSG_ERROR([Your compiler doesn't support c99 mid-block declarations. This is required as of Tor 0.2.6.x])
fi

AC_CACHE_CHECK([for working C99 designated initializers],
      tor_cv_c_c99_designated_init,
      [AC_COMPILE_IFELSE(
         [AC_LANG_PROGRAM([struct s { int a; int b; };],
  	       [[ struct s ss = { .b = 5, .a = 6 }; ]])],
	 [tor_cv_c_c99_designated_init=yes],
	 [tor_cv_c_c99_designated_init=no] )])

if test "$tor_cv_c_c99_designated_init" != "yes"; then
  AC_MSG_ERROR([Your compiler doesn't support c99 designated initializers. This is required as of Tor 0.2.6.x])
fi

saved_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Werror"
AC_CACHE_CHECK([for __attribute__((fallthrough))],
      tor_cv_c_attr_fallthrough,
      [AC_COMPILE_IFELSE(
         [AC_LANG_PROGRAM([extern int x; void fn(void) ;],
	       [[ switch (x) { case 1: fn(); __attribute__((fallthrough));
                               case 2: fn(); break; } ]])],
	 [tor_cv_c_attr_fallthrough=yes],
	 [tor_cv_c_attr_fallthrough=no] )])
CFLAGS="$saved_CFLAGS"

if test "$tor_cv_c_attr_fallthrough" = "yes"; then
  AC_DEFINE(HAVE_ATTR_FALLTHROUGH, [1], [defined if we have the fallthrough attribute.])
fi

TORUSER=_tor
AC_ARG_WITH(tor-user,
        AS_HELP_STRING(--with-tor-user=NAME, [specify username for tor daemon]),
        [
           TORUSER=$withval
        ]
)
AC_SUBST(TORUSER)

TORGROUP=_tor
AC_ARG_WITH(tor-group,
        AS_HELP_STRING(--with-tor-group=NAME, [specify group name for tor daemon]),
        [
           TORGROUP=$withval
        ]
)
AC_SUBST(TORGROUP)


dnl If _WIN32 is defined and non-zero, we are building for win32
AC_MSG_CHECKING([for win32])
AC_RUN_IFELSE([AC_LANG_SOURCE([
int main(int c, char **v) {
#ifdef _WIN32
#if _WIN32
  return 0;
#else
  return 1;
#endif
#else
  return 2;
#endif
}])],
bwin32=true; AC_MSG_RESULT([yes]),
bwin32=false; AC_MSG_RESULT([no]),
bwin32=cross; AC_MSG_RESULT([cross])
)

if test "$bwin32" = "cross"; then
AC_MSG_CHECKING([for win32 (cross)])
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#ifdef _WIN32
int main(int c, char **v) {return 0;}
#else
#error
int main(int c, char **v) {return x(y);}
#endif
])],
bwin32=true; AC_MSG_RESULT([yes]),
bwin32=false; AC_MSG_RESULT([no]))
fi

AH_BOTTOM([
#ifdef _WIN32
/* Defined to access windows functions and definitions for >=WinVista */
# ifndef WINVER
#  define WINVER 0x0600
# endif

/* Defined to access _other_ windows functions and definitions for >=WinVista */
# ifndef _WIN32_WINNT
#  define _WIN32_WINNT 0x0600
# endif

/* Defined to avoid including some windows headers as part of Windows.h */
# ifndef WIN32_LEAN_AND_MEAN
#  define WIN32_LEAN_AND_MEAN 1
# endif
#endif
])

AM_CONDITIONAL(WIN32, test "x$bwin32" = "xtrue")
AM_CONDITIONAL(BUILD_NT_SERVICES, test "x$bwin32" = "xtrue")
AM_CONDITIONAL(BUILD_LIBTORRUNNER, test "x$bwin32" != "xtrue")

dnl Enable C99 when compiling with MIPSpro
AC_MSG_CHECKING([for MIPSpro compiler])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, [
#if (defined(__sgi) && defined(_COMPILER_VERSION))
#error
  return x(y);
#endif
])],
bmipspro=false; AC_MSG_RESULT(no),
bmipspro=true; AC_MSG_RESULT(yes))

if test "$bmipspro" = "true"; then
  CFLAGS="$CFLAGS -c99"
fi

AC_C_BIGENDIAN

AC_ARG_VAR([TOR_RUST_TARGET], [Rust target, must be specified when cross-compiling (HOST != BUILD). example: i686-pc-windows-gnu])

if test "x$enable_rust" = "xyes"; then
  AC_ARG_VAR([RUSTC], [path to the rustc binary])
  AC_CHECK_PROG([RUSTC], [rustc], [rustc],[no])
  if test "x$RUSTC" = "xno"; then
    AC_MSG_ERROR([rustc unavailable but rust integration requested.])
  fi

  AC_ARG_VAR([CARGO], [path to the cargo binary])
  AC_CHECK_PROG([CARGO], [cargo], [cargo],[no])
  if test "x$CARGO" = "xno"; then
    AC_MSG_ERROR([cargo unavailable but rust integration requested.])
  fi

  AC_DEFINE([HAVE_RUST], 1, [have Rust])
  if test "x$enable_fatal_warnings" = "xyes"; then
    RUST_WARN=
  else
    RUST_WARN=#
  fi
  if test "x$enable_cargo_online_mode" = "xyes"; then
    CARGO_ONLINE=
    RUST_DL=#
  else
    CARGO_ONLINE=--frozen
    RUST_DL=

    dnl When we're not allowed to touch the network, we need crate dependencies
    dnl locally available.
    AC_MSG_CHECKING([rust crate dependencies])
    AC_ARG_VAR([TOR_RUST_DEPENDENCIES], [path to directory with local crate mirror])
    if test "x$TOR_RUST_DEPENDENCIES" = "x"; then
      TOR_RUST_DEPENDENCIES="${srcdir}/src/ext/rust/crates"
    fi
    dnl Check whether the path exists before we try to cd into it.
    if test ! -d "$TOR_RUST_DEPENDENCIES"; then
      AC_MSG_ERROR([Rust dependency directory $TOR_RUST_DEPENDENCIES does not exist. Specify a dependency directory using the TOR_RUST_DEPENDENCIES variable or allow cargo to fetch crates using --enable-cargo-online-mode.])
      ERRORED=1
    fi
    dnl Make the path absolute, since we'll be using it from within a
    dnl subdirectory.
    TOR_RUST_DEPENDENCIES=$(cd "$TOR_RUST_DEPENDENCIES" ; pwd)

    for dep in $rust_crates; do
      if test ! -d "$TOR_RUST_DEPENDENCIES"/"$dep"; then
        AC_MSG_ERROR([Failure to find rust dependency $TOR_RUST_DEPENDENCIES/$dep. Specify a dependency directory using the TOR_RUST_DEPENDENCIES variable or allow cargo to fetch crates using --enable-cargo-online-mode.])
        ERRORED=1
      fi
    done
    if test "x$ERRORED" = "x"; then
      AC_MSG_RESULT([yes])
    fi
  fi

  dnl For now both MSVC and MinGW rust libraries will output static libs with
  dnl the MSVC naming convention.
  if test "$bwin32" = "true"; then
    tor_rust_static_name=tor_rust.lib
  else
    tor_rust_static_name=libtor_rust.a
  fi

  AC_CANONICAL_BUILD

  if test -n "$TOR_RUST_TARGET"; then
    if test "$host" = "$build"; then
      AC_MSG_ERROR([HOST = BUILD is invalid if TOR_RUST_TARGET is specified, see configure --help for more information.])
    fi
    RUST_TARGET_PROP="target = '$TOR_RUST_TARGET'"
    TOR_RUST_LIB_PATH="src/rust/target/$TOR_RUST_TARGET/release/$tor_rust_static_name"
  else
    if test "$host" != "$build"; then
      AC_MSG_ERROR([TOR_RUST_TARGET must be specified when cross-compiling with Rust enabled.])
    fi
    RUST_TARGET_PROP=
    TOR_RUST_LIB_PATH="src/rust/target/release/$tor_rust_static_name"
  fi

  AC_SUBST(RUST_TARGET_PROP)
  AC_SUBST(TOR_RUST_LIB_PATH)
  AC_SUBST(CARGO_ONLINE)
  AC_SUBST(RUST_WARN)
  AC_SUBST(RUST_DL)

  dnl Let's check the rustc version, too
  AC_MSG_CHECKING([rust version])
  RUSTC_VERSION=`$RUSTC --version`
  RUSTC_VERSION_MAJOR=`$RUSTC --version | cut -d ' ' -f 2 | cut -d '.' -f 1`
  RUSTC_VERSION_MINOR=`$RUSTC --version | cut -d ' ' -f 2 | cut -d '.' -f 2`
  if test "x$RUSTC_VERSION_MAJOR" = "x" -o "x$RUSTC_VERSION_MINOR" = "x"; then
    AC_MSG_ERROR([rustc version couldn't be identified])
  fi
  if test "$RUSTC_VERSION_MAJOR" -lt 2 -a "$RUSTC_VERSION_MINOR" -lt 31; then
    AC_MSG_ERROR([rustc must be at least version 1.31.0])
  fi
  AC_MSG_RESULT([$RUSTC_VERSION])
fi

AC_SEARCH_LIBS(socket, [socket network])
AC_SEARCH_LIBS(gethostbyname, [nsl])
AC_SEARCH_LIBS(dlopen, [dl])
AC_SEARCH_LIBS(inet_aton, [resolv])
AC_SEARCH_LIBS(backtrace, [execinfo])
saved_LIBS="$LIBS"
AC_SEARCH_LIBS([clock_gettime], [rt])
if test "$LIBS" != "$saved_LIBS"; then
   # Looks like we need -lrt for clock_gettime().
   have_rt=yes
fi

if test "$bwin32" = "false"; then
  AC_SEARCH_LIBS(pthread_create, [pthread])
  AC_SEARCH_LIBS(pthread_detach, [pthread])
fi

AM_CONDITIONAL(THREADS_WIN32, test "$bwin32" = "true")
AM_CONDITIONAL(THREADS_PTHREADS, test "$bwin32" = "false")

AC_CHECK_FUNCS(
	_NSGetEnviron \
	RtlSecureZeroMemory \
	SecureZeroMemory \
	accept4 \
	backtrace \
	backtrace_symbols_fd \
	eventfd \
	explicit_bzero \
	timingsafe_memcmp \
	flock \
	fsync \
	ftime \
	get_current_dir_name \
	getaddrinfo \
	getdelim \
	getifaddrs \
	getline \
	getrlimit \
	gettimeofday \
	gmtime_r \
	gnu_get_libc_version \
	inet_aton \
	ioctl \
	issetugid \
	llround \
	localtime_r \
	lround \
	madvise \
	memmem \
	memset_s \
	minherit \
	mmap \
	pipe \
	pipe2 \
	prctl \
	readpassphrase \
	rint \
	sigaction \
	socketpair \
	statvfs \
	strncasecmp \
	strcasecmp \
	strlcat \
	strlcpy \
	strnlen \
	strptime \
	strtok_r \
	strtoull \
	sysconf \
	sysctl \
	truncate \
	uname \
	usleep \
	vasprintf \
	_vscprintf
)

# Apple messed up when they added some functions: they
# forgot to decorate them with appropriate AVAILABLE_MAC_OS_VERSION
# checks.

# We should only probe for these functions if we are sure that we
# are not targeting OS X 10.9 or earlier.
AC_MSG_CHECKING([for a pre-Yosemite OS X build target])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#ifdef __APPLE__
#  include <AvailabilityMacros.h>
#  ifndef MAC_OS_X_VERSION_10_10
#    define MAC_OS_X_VERSION_10_10 101000
#  endif
#  if defined(MAC_OS_X_VERSION_MIN_REQUIRED)
#    if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_10
#      error "Running on Mac OS X 10.9 or earlier"
#    endif
#  endif
#endif
]], [[]])],
   [on_macos_pre_10_10=no ; AC_MSG_RESULT([no])],
   [on_macos_pre_10_10=yes; AC_MSG_RESULT([yes])])

if test "$on_macos_pre_10_10" = "no"; then
  AC_CHECK_FUNCS(
        mach_approximate_time \
  )
fi

# We should only probe for these functions if we are sure that we
# are not targeting OSX 10.11 or earlier.
AC_MSG_CHECKING([for a pre-Sierra OSX build target])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#ifdef __APPLE__
#  include <AvailabilityMacros.h>
#  ifndef MAC_OS_X_VERSION_10_12
#    define MAC_OS_X_VERSION_10_12 101200
#  endif
#  if defined(MAC_OS_X_VERSION_MIN_REQUIRED)
#    if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
#      error "Running on Mac OSX 10.11 or earlier"
#    endif
#  endif
#endif
]], [[]])],
   [on_macos_pre_10_12=no ; AC_MSG_RESULT([no])],
   [on_macos_pre_10_12=yes; AC_MSG_RESULT([yes])])

if test "$on_macos_pre_10_12" = "no"; then
  AC_CHECK_FUNCS(
        clock_gettime \
        getentropy \
  )
fi

if test "$bwin32" != "true"; then
  AC_CHECK_HEADERS(pthread.h)
  AC_CHECK_FUNCS(pthread_create)
  AC_CHECK_FUNCS(pthread_condattr_setclock)
fi

if test "$bwin32" = "true"; then
  AC_CHECK_DECLS([SecureZeroMemory, _getwch], , , [
#include <windows.h>
#include <conio.h>
#include <wchar.h>
                 ])
fi

AM_CONDITIONAL(BUILD_READPASSPHRASE_C,
  test "x$ac_cv_func_readpassphrase" = "xno" && test "$bwin32" = "false")

AC_CHECK_FUNCS(glob)

AC_MSG_CHECKING([whether free(NULL) works])
AC_RUN_IFELSE([AC_LANG_PROGRAM([
  #include <stdlib.h>
], [
char *p = NULL;
free(p);
])],
[free_null_ok=true; AC_MSG_RESULT(yes)],
[free_null_ok=false; AC_MSG_RESULT(no)],
[free_null_ok=cross; AC_MSG_RESULT(cross)])

if test "$free_null_ok" = "false"; then
   AC_MSG_ERROR([Your libc implementation doesn't allow free(NULL), as required by C99.])
fi

dnl ------------------------------------------------------
dnl Where do you live, libevent?  And how do we call you?

if test "$bwin32" = "true"; then
  TOR_LIB_WS32=-lws2_32
  TOR_LIB_IPHLPAPI=-liphlpapi
  TOR_LIB_SHLWAPI=-lshlwapi
  # Some of the cargo-cults recommend -lwsock32 as well, but I don't
  # think it's actually necessary.
  TOR_LIB_GDI=-lgdi32
  TOR_LIB_USERENV=-luserenv
  TOR_LIB_BCRYPT=-lbcrypt
  TOR_LIB_CRYPT32=-lcrypt32
else
  TOR_LIB_WS32=
  TOR_LIB_GDI=
  TOR_LIB_USERENV=
fi
AC_SUBST(TOR_LIB_WS32)
AC_SUBST(TOR_LIB_GDI)
AC_SUBST(TOR_LIB_IPHLPAPI)
AC_SUBST(TOR_LIB_BCRYPT)
AC_SUBST(TOR_LIB_CRYPT32)
AC_SUBST(TOR_LIB_SHLWAPI)
AC_SUBST(TOR_LIB_USERENV)

tor_libevent_pkg_redhat="libevent"
tor_libevent_pkg_debian="libevent-dev"
tor_libevent_devpkg_redhat="libevent-devel"
tor_libevent_devpkg_debian="libevent-dev"

dnl On Gnu/Linux or any place we require it, we'll add librt to the Libevent
dnl linking for static builds.
STATIC_LIBEVENT_FLAGS=""
if test "$enable_static_libevent" = "yes"; then
    if test "$have_rt" = "yes"; then
      STATIC_LIBEVENT_FLAGS=" -lrt "
    fi
fi

TOR_SEARCH_LIBRARY(libevent, $trylibeventdir, [-levent $STATIC_LIBEVENT_FLAGS $TOR_LIB_IPHLPAPI $TOR_LIB_BCRYPT $TOR_LIB_WS32], [
#ifdef _WIN32
#include <winsock2.h>
#endif
#include <sys/time.h>
#include <sys/types.h>
#include <event2/event.h>], [
#ifdef _WIN32
#include <winsock2.h>
#endif
struct event_base;
struct event_base *event_base_new(void);
void event_base_free(struct event_base *);],
    [
#ifdef _WIN32
{WSADATA d; WSAStartup(0x101,&d); }
#endif
event_base_free(event_base_new());
], [--with-libevent-dir], [/opt/libevent])

dnl Determine the incantation needed to link libevent.
save_LIBS="$LIBS"
save_LDFLAGS="$LDFLAGS"
save_CPPFLAGS="$CPPFLAGS"

LIBS="$STATIC_LIBEVENT_FLAGS $TOR_LIB_WS32 $save_LIBS"
LDFLAGS="$TOR_LDFLAGS_libevent $LDFLAGS"
CPPFLAGS="$TOR_CPPFLAGS_libevent $CPPFLAGS"

AC_CHECK_HEADERS(event2/event.h event2/dns.h event2/bufferevent_ssl.h)

if test "$enable_static_libevent" = "yes"; then
   if test "$tor_cv_library_libevent_dir" = "(system)"; then
     AC_MSG_ERROR("You must specify an explicit --with-libevent-dir=x option when using --enable-static-libevent")
   else
     TOR_LIBEVENT_LIBS="$TOR_LIBDIR_libevent/libevent.a $STATIC_LIBEVENT_FLAGS"
   fi
else
     if test "x$ac_cv_header_event2_event_h" = "xyes"; then
       AC_SEARCH_LIBS(event_new, [event event_core], , AC_MSG_ERROR("libevent2 is installed but linking it failed while searching for event_new"))
       AC_SEARCH_LIBS(evdns_base_new, [event event_extra], , AC_MSG_ERROR("libevent2 is installed but linking it failed while searching for evdns_base_new"))

       if test "$ac_cv_search_event_new" != "none required"; then
         TOR_LIBEVENT_LIBS="$ac_cv_search_event_new"
       fi
       if test "$ac_cv_search_evdns_base_new" != "none required"; then
         TOR_LIBEVENT_LIBS="$ac_cv_search_evdns_base_new $TOR_LIBEVENT_LIBS"
       fi
     else
       AC_MSG_ERROR("libevent2 is required but the headers could not be found")
     fi
fi

dnl Now check for particular libevent functions.
AC_CHECK_FUNCS([evutil_secure_rng_set_urandom_device_file \
                evutil_secure_rng_add_bytes \
                evdns_base_get_nameserver_addr \

])

LIBS="$save_LIBS"
LDFLAGS="$save_LDFLAGS"
CPPFLAGS="$save_CPPFLAGS"

dnl Check that libevent is at least at version 2.0.10, the first stable
dnl release of its series
CPPFLAGS="$CPPFLAGS $TOR_CPPFLAGS_libevent"
AC_MSG_CHECKING([whether Libevent is new enough])
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <event2/event.h>
#if !defined(LIBEVENT_VERSION_NUMBER) || LIBEVENT_VERSION_NUMBER < 0x02000a00
#error
int x = y(zz);
#else
int x = 1;
#endif
])], [ AC_MSG_RESULT([yes]) ],
   [ AC_MSG_RESULT([no])
     AC_MSG_ERROR([Libevent is not new enough.  We require 2.0.10-stable or later]) ] )

LIBS="$save_LIBS"
LDFLAGS="$save_LDFLAGS"
CPPFLAGS="$save_CPPFLAGS"

AC_SUBST(TOR_LIBEVENT_LIBS)

dnl ------------------------------------------------------
dnl Where do you live, libm?

dnl On some platforms (Haiku/BeOS) the math library is
dnl part of libroot. In which case don't link against lm
TOR_LIB_MATH=""
save_LIBS="$LIBS"
AC_SEARCH_LIBS(pow, [m], , AC_MSG_ERROR([Could not find pow in libm or libc.]))
if test "$ac_cv_search_pow" != "none required"; then
    TOR_LIB_MATH="$ac_cv_search_pow"
fi
LIBS="$save_LIBS"
AC_SUBST(TOR_LIB_MATH)

dnl ------------------------------------------------------
dnl Hello, NSS.  You're new around here.
if test "x$enable_nss" = "xyes"; then
  PKG_CHECK_MODULES(NSS,
     [nss],
     [have_nss=yes],
     [have_nss=no; AC_MSG_ERROR([You asked for NSS but I can't find it, $pkg_config_user_action, or set NSS_CFLAGS and NSS_LIBS.])])
  AC_SUBST(NSS_CFLAGS)
  AC_SUBST(NSS_LIBS)
fi

dnl ------------------------------------------------------
dnl Where do you live, openssl?  And how do we call you?

if test "x$enable_nss" != "xyes"; then

tor_openssl_pkg_redhat="openssl"
tor_openssl_pkg_debian="libssl-dev"
tor_openssl_devpkg_redhat="openssl-devel"
tor_openssl_devpkg_debian="libssl-dev"

ALT_openssl_WITHVAL=""
AC_ARG_WITH(ssl-dir,
  AS_HELP_STRING(--with-ssl-dir=PATH, [obsolete alias for --with-openssl-dir]),
  [
      if test "x$withval" != "xno" && test "x$withval" != "x"; then
         ALT_openssl_WITHVAL="$withval"
      fi
  ])

AC_MSG_NOTICE([Now, we'll look for OpenSSL >= 1.0.1])
TOR_SEARCH_LIBRARY(openssl, $tryssldir, [-lssl -lcrypto $TOR_LIB_GDI $TOR_LIB_WS32 $TOR_LIB_CRYPT32],
    [#include <openssl/ssl.h>
     char *getenv(const char *);],
    [struct ssl_cipher_st;
     unsigned SSL_CIPHER_get_id(const struct ssl_cipher_st *);
     char *getenv(const char *);],
    dnl This funny-looking test program calls getenv, so that the compiler
    dnl will neither make code that call SSL_CIPHER_get_id(NULL) [producing
    dnl a crash], nor optimize out the call to SSL_CIPHER_get_id().
    dnl We look for SSL_cipher_get_id() because it is present in
    dnl OpenSSL >=1.0.1, because it is not deprecated, and because Tor
    dnl depends on it.
    [if (getenv("THIS_SHOULDNT_BE_SET_X201803")) SSL_CIPHER_get_id((void *)0);], [],
    [/usr/local/opt/openssl /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /opt/openssl])

if test "$enable_static_openssl" = "yes"; then
   if test "$tor_cv_library_openssl_dir" = "(system)"; then
     AC_MSG_ERROR("You must specify an explicit --with-openssl-dir=x option when using --enable-static-openssl")
   else
     TOR_OPENSSL_LIBS="$TOR_LIBDIR_openssl/libssl.a $TOR_LIBDIR_openssl/libcrypto.a $TOR_LIB_WS32 $TOR_LIB_CRYPT32 $TOR_LIB_BCRYPT"
   fi
else
     TOR_OPENSSL_LIBS="-lssl -lcrypto"
fi
AC_SUBST(TOR_OPENSSL_LIBS)

dnl Now validate openssl, and check for particular openssl functions.
save_LIBS="$LIBS"
save_LDFLAGS="$LDFLAGS"
save_CPPFLAGS="$CPPFLAGS"
LIBS="$TOR_OPENSSL_LIBS $LIBS"
LDFLAGS="$TOR_LDFLAGS_openssl $LDFLAGS"
CPPFLAGS="$TOR_CPPFLAGS_openssl $CPPFLAGS"