configure.in

dnl Copyright (c) 2001-2004, Roger Dingledine
dnl Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson
dnl Copyright (c) 2007-2012, The Tor Project, Inc.
dnl See LICENSE for licensing information

AC_INIT
AM_INIT_AUTOMAKE(tor, 0.2.4.0-alpha-dev)
AM_CONFIG_HEADER(orconfig.h)

AC_CANONICAL_HOST

if test -f /etc/redhat-release ; then
  if test -f /usr/kerberos/include ; then
    CPPFLAGS="$CPPFLAGS -I/usr/kerberos/include"
  fi
fi

# Not a no-op; we want to make sure that CPPFLAGS is set before we use
# the += operator on it in src/or/Makefile.am
CPPFLAGS="$CPPFLAGS -I\${top_srcdir}/src/common"

#XXXX020 We should make these enabled or not, before 0.2.0.x-final
AC_ARG_ENABLE(buf-freelists,
   AS_HELP_STRING(--disable-buf-freelists, disable freelists for buffer RAM))
AC_ARG_ENABLE(openbsd-malloc,
   AS_HELP_STRING(--enable-openbsd-malloc, Use malloc code from openbsd.  Linux only))
AC_ARG_ENABLE(instrument-downloads,
   AS_HELP_STRING(--enable-instrument-downloads, Instrument downloads of directory resources etc.))
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))

if test "$enable_static_tor" = "yes"; then
  enable_static_libevent="yes";
  enable_static_openssl="yes";
  enable_static_zlib="yes";
  CFLAGS="$CFLAGS -static"
fi

if test x$enable_buf_freelists != xno; then
  AC_DEFINE(ENABLE_BUF_FREELISTS, 1,
            [Defined if we try to use freelists for buffer RAM chunks])
fi
AM_CONDITIONAL(USE_OPENBSD_MALLOC, test x$enable_openbsd_malloc = xyes)
if test x$enable_instrument_downloads = xyes; then
  AC_DEFINE(INSTRUMENT_DOWNLOADS, 1,
            [Defined if we want to keep track of how much of each kind of resource we download.])
fi

AC_ARG_ENABLE(transparent,
     AS_HELP_STRING(--disable-transparent, disable transparent proxy support),
     [case "${enableval}" in
        yes) transparent=true ;;
        no)  transparent=false ;;
        *) AC_MSG_ERROR(bad value for --enable-transparent) ;;
      esac], [transparent=true])

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])

# By default, we're not ready to ship a NAT-PMP aware Tor
AC_ARG_ENABLE(nat-pmp,
     AS_HELP_STRING(--enable-nat-pmp, enable NAT-PMP support),
     [case "${enableval}" in
        yes) natpmp=true ;;
        no)  natpmp=false ;;
        * ) AC_MSG_ERROR(bad value for --enable-nat-pmp) ;;
      esac], [natpmp=false])

# By default, we're not ready to ship a UPnP aware Tor
AC_ARG_ENABLE(upnp,
     AS_HELP_STRING(--enable-upnp, enable UPnP support),
     [case "${enableval}" in
        yes) upnp=true ;;
        no)  upnp=false ;;
        * ) AC_MSG_ERROR(bad value for --enable-upnp) ;;
      esac], [upnp=false])


AC_ARG_ENABLE(threads,
     AS_HELP_STRING(--disable-threads, disable multi-threading support))

if test x$enable_threads = x; then
   case $host in
    *-*-solaris* )
     # Don't try multithreading on solaris -- cpuworkers seem to lock.
     AC_MSG_NOTICE([You are running Solaris; Sometimes threading makes
cpu workers lock up here, so I will disable threads.])
     enable_threads="no";;
    *)
     enable_threads="yes";;
   esac
fi

if test "$enable_threads" = "yes"; then
  AC_DEFINE(ENABLE_THREADS, 1, [Defined if we will try to use multithreading])
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, enable verbose warnings))
AC_ARG_ENABLE(gcc-warnings-advisory,
     AS_HELP_STRING(--enable-gcc-warnings-advisory, [enable verbose warnings, excluding -Werror]))

dnl Adam shostack suggests the following for Windows:
dnl -D_FORTIFY_SOURCE=2 -fstack-protector-all
dnl Others suggest '/gs /safeseh /nxcompat /dynamicbase' for non-gcc on Windows
dnl This requires that we use gcc and that we add -O2 to the CFLAGS.
AC_ARG_ENABLE(gcc-hardening,
    AS_HELP_STRING(--disable-gcc-hardening, disable compiler security checks))

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

# Tor2web mode flag
AC_ARG_ENABLE(tor2web-mode,
     AS_HELP_STRING(--enable-tor2web-mode, support tor2web non-anonymous mode),
[if test x$enableval = xyes; then
    CFLAGS="$CFLAGS -D ENABLE_TOR2WEB_MODE=1"
fi])

AC_ARG_ENABLE(bufferevents,
     AS_HELP_STRING(--enable-bufferevents, use Libevent's buffered IO.))

dnl check for the correct "ar" when cross-compiling
AN_MAKEVAR([AR], [AC_PROG_AR])
AN_PROGRAM([ar], [AC_PROG_AR])
AC_DEFUN([AC_PROG_AR], [AC_CHECK_TOOL([AR], [ar], [ar])])
AC_PROG_AR

AC_PROG_CC
AC_PROG_CPP
AC_PROG_MAKE_SET
AC_PROG_RANLIB

dnl autoconf 2.59 appears not to support AC_PROG_SED
AC_CHECK_PROG([SED],[sed],[sed],[/bin/false])

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

AM_CONDITIONAL(USE_ASCIIDOC, test x$asciidoc = xtrue)

AM_CONDITIONAL(USE_FW_HELPER, test x$natpmp = xtrue || test x$upnp = xtrue)
AM_CONDITIONAL(NAT_PMP, test x$natpmp = xtrue)
AM_CONDITIONAL(MINIUPNPC, test x$upnp = xtrue)
AM_PROG_CC_C_O

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_PATH_PROG([SHA1SUM], [sha1sum], none)
AC_PATH_PROG([OPENSSL], [openssl], none)

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

TORGROUP=_tor
AC_ARG_WITH(tor-group,
        [  --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

AM_CONDITIONAL(BUILD_NT_SERVICES, 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_SEARCH_LIBS(socket, [socket network])
AC_SEARCH_LIBS(gethostbyname, [nsl])
AC_SEARCH_LIBS(dlopen, [dl])
AC_SEARCH_LIBS(inet_aton, [resolv])
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 "$enable_threads" = "yes"; then
  AC_SEARCH_LIBS(pthread_create, [pthread])
  AC_SEARCH_LIBS(pthread_detach, [pthread])
fi

dnl -------------------------------------------------------------------
dnl Check for functions before libevent, since libevent-1.2 apparently
dnl exports strlcpy without defining it in a header.

AC_CHECK_FUNCS(
        _NSGetEnviron \
        accept4 \
        clock_gettime \
        flock \
        ftime \
        getaddrinfo \
        getifaddrs \
        getrlimit \
        gettimeofday \
        gmtime_r \
        inet_aton \
        ioctl \
        localtime_r \
        lround \
        memmem \
        prctl \
        rint \
        socketpair \
        strlcat \
        strlcpy \
        strptime \
        strtok_r \
        strtoull \
        sysconf \
        uname \
        vasprintf \
)

using_custom_malloc=no
if test x$enable_openbsd_malloc = xyes ; then
   AC_DEFINE(HAVE_MALLOC_GOOD_SIZE, 1, [Defined if we have the malloc_good_size function])
   using_custom_malloc=yes
fi
if test x$tcmalloc = xyes ; then
   using_custom_malloc=yes
fi
if test $using_custom_malloc = no ; then
   AC_CHECK_FUNCS(mallinfo malloc_good_size malloc_usable_size)
fi

if test "$enable_threads" = "yes"; then
  AC_CHECK_HEADERS(pthread.h)
  AC_CHECK_FUNCS(pthread_create)
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
  # Some of the cargo-cults recommend -lwsock32 as well, but I don't
  # think it's actually necessary.
  TOR_LIB_GDI=-lgdi32
else
  TOR_LIB_WS32=
  TOR_LIB_GDI=
fi
AC_SUBST(TOR_LIB_WS32)
AC_SUBST(TOR_LIB_GDI)
AC_SUBST(TOR_LIB_IPHLPAPI)

dnl We need to do this before we try our disgusting hack below.
AC_CHECK_HEADERS([sys/types.h])

dnl This is a disgusting hack so we safely include older libevent headers.
AC_CHECK_TYPE(u_int64_t, unsigned long long)
AC_CHECK_TYPE(u_int32_t, unsigned long)
AC_CHECK_TYPE(u_int16_t, unsigned short)
AC_CHECK_TYPE(u_int8_t, unsigned char)

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_WS32], [
#ifdef _WIN32
#include <winsock2.h>
#endif
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <event.h>], [
#ifdef _WIN32
#include <winsock2.h>
#endif
void exit(int); void *event_init(void);],
    [
#ifdef _WIN32
{WSADATA d; WSAStartup(0x101,&d); }
#endif
event_init(); exit(0);
], [--with-libevent-dir], [/opt/libevent])

dnl Now check for particular libevent functions.
save_LIBS="$LIBS"
save_LDFLAGS="$LDFLAGS"
save_CPPFLAGS="$CPPFLAGS"
LIBS="-levent $STATIC_LIBEVENT_FLAGS $TOR_LIB_WS32 $LIBS"
LDFLAGS="$TOR_LDFLAGS_libevent $LDFLAGS"
CPPFLAGS="$TOR_CPPFLAGS_libevent $CPPFLAGS"
AC_CHECK_FUNCS(event_get_version event_get_version_number event_get_method event_set_log_callback evdns_set_outgoing_bind_address event_base_loopexit)
AC_CHECK_MEMBERS([struct event.min_heap_idx], , ,
[#include <event.h>
])

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

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


AM_CONDITIONAL(USE_EXTERNAL_EVDNS, test x$ac_cv_header_event2_dns_h = xyes)

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
     TOR_LIBEVENT_LIBS="-levent"
fi

dnl This isn't the best test for Libevent 2.0.3-alpha.  Once it's released,
dnl we can do much better.
if test "$enable_bufferevents" = "yes" ; then
  if test "$ac_cv_header_event2_bufferevent_ssl_h" != "yes" ; then
    AC_MSG_ERROR([You've asked for bufferevent support, but you're using a version of Libevent without SSL support.  This won't work.  We need Libevent 2.0.8-rc or later, and you don't seem to even have Libevent 2.0.3-alpha.])
  else

    CPPFLAGS="$CPPFLAGS $TOR_CPPFLAGS_libevent"

    # Check for the right version.  First see if version detection works.
    AC_MSG_CHECKING([whether we can detect the Libevent version])
    AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <event2/event.h>
#if !defined(LIBEVENT_VERSION_NUMBER) || LIBEVENT_VERSION_NUMBER < 10
#error
int x = y(zz);
#else
int x = 1;
#endif
  ])], [event_version_number_works=yes; AC_MSG_RESULT([yes]) ],
     [event_version_number_works=no;  AC_MSG_RESULT([no])])
    if test "$event_version_number_works" != 'yes'; then
      AC_MSG_WARN([Version detection on Libevent seems broken.  Your Libevent installation is probably screwed up or very old.])
    else
      AC_MSG_CHECKING([whether Libevent is new enough for bufferevents])
      AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <event2/event.h>
#if !defined(LIBEVENT_VERSION_NUMBER) || LIBEVENT_VERSION_NUMBER < 0x02000d00
#error
int x = y(zz);
#else
int x = 1;
#endif
   ])], [ AC_MSG_RESULT([yes]) ],
      [ AC_MSG_RESULT([no])
        AC_MSG_ERROR([Libevent does not seem new enough to support bufferevents.  We require 2.0.13-stable or later]) ] )
    fi
  fi
fi

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

AM_CONDITIONAL(USE_BUFFEREVENTS, test "$enable_bufferevents" = "yes")
if test "$enable_bufferevents" = "yes"; then
  AC_DEFINE(USE_BUFFEREVENTS, 1, [Defined if we're going to use Libevent's buffered IO API])
  if test "$enable_static_libevent" = "yes"; then
    TOR_LIBEVENT_LIBS="$TOR_LIBDIR_libevent/libevent_openssl.a $TOR_LIBEVENT_LIBS"
  else
    TOR_LIBEVENT_LIBS="-levent_openssl $TOR_LIBEVENT_LIBS"
  fi
fi
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 Where do you live, openssl?  And how do we call you?

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

ALT_openssl_WITHVAL=""
AC_ARG_WITH(ssl-dir,
  [  --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
  ])

TOR_SEARCH_LIBRARY(openssl, $tryssldir, [-lssl -lcrypto $TOR_LIB_GDI],
    [#include <openssl/rand.h>],
    [void RAND_add(const void *buf, int num, double entropy);],
    [RAND_add((void*)0,0,0); exit(0);], [],
    [/usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/athena /opt/openssl])

dnl XXXX check for OPENSSL_VERSION_NUMBER == SSLeay()

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"
   fi
else
     TOR_OPENSSL_LIBS="-lssl -lcrypto"
fi
AC_SUBST(TOR_OPENSSL_LIBS)

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

tor_zlib_pkg_redhat="zlib"
tor_zlib_pkg_debian="zlib1g"
tor_zlib_devpkg_redhat="zlib-devel"
tor_zlib_devpkg_debian="zlib1g-dev"

TOR_SEARCH_LIBRARY(zlib, $tryzlibdir, [-lz],
    [#include <zlib.h>],
    [const char * zlibVersion(void);],
    [zlibVersion(); exit(0);], [--with-zlib-dir],
    [/opt/zlib])

if test "$enable_static_zlib" = "yes"; then
   if test "$tor_cv_library_zlib_dir" = "(system)"; then
     AC_MSG_ERROR("You must specify an explicit --with-zlib-dir=x option when
 using --enable-static-zlib")
   else
     TOR_ZLIB_LIBS="$TOR_LIBDIR_zlib/libz.a"
   fi
else
     TOR_ZLIB_LIBS="-lz"
fi
AC_SUBST(TOR_ZLIB_LIBS)

dnl ---------------------------------------------------------------------
dnl Now that we know about our major libraries, we can check for compiler
dnl and linker hardening options.  We need to do this with the libraries known,
dnl since sometimes the linker will like an option but not be willing to
dnl use it with a build of a library.

all_ldflags_for_check="$TOR_LDFLAGS_zlib $TOR_LDFLAGS_openssl $TOR_LDFLAGS_libevent"
all_libs_for_check="$TOR_ZLIB_LIBS $TOR_LIB_MATH $TOR_LIBEVENT_LIBS $TOR_OPENSSL_LIBS $TOR_LIB_WS32 $TOR_LIB_GDI"

AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
#if !defined(__clang__)
#error
#endif])], have_clang=yes, have_clang=no)

if test x$enable_gcc_hardening != xno; then
    CFLAGS="$CFLAGS -D_FORTIFY_SOURCE=2"
    if test x$have_clang = xyes; then
        TOR_CHECK_CFLAGS(-Qunused-arguments)
    fi
    TOR_CHECK_CFLAGS(-fstack-protector-all)
    TOR_CHECK_CFLAGS(-Wstack-protector)
    TOR_CHECK_CFLAGS(-fwrapv)
    TOR_CHECK_CFLAGS(--param ssp-buffer-size=1)
    if test "$bwin32" = "false"; then
       TOR_CHECK_CFLAGS(-fPIE)
       TOR_CHECK_LDFLAGS(-pie, "$all_ldflags_for_check", "$all_libs_for_check")
    fi
fi

if test x$enable_linker_hardening != xno; then
    TOR_CHECK_LDFLAGS(-z relro -z now, "$all_ldflags_for_check", "$all_libs_for_check")
fi

dnl ------------------------------------------------------
dnl Where do you live, libnatpmp?  And how do we call you?
dnl There are no packages for Debian or Redhat as of this patch

if test "$natpmp" = "true"; then
    AC_DEFINE(NAT_PMP, 1, [Define to 1 if we are building with nat-pmp.])
    TOR_SEARCH_LIBRARY(libnatpmp, $trylibnatpmpdir, [-lnatpmp $TOR_LIB_WS32 $TOR_LIB_IPHLPAPI],
        [#include <natpmp.h>],
        [#ifdef _WIN32
         #define STATICLIB
         #endif
         #include <natpmp.h>],
        [   int r;
            natpmp_t natpmp;
            natpmpresp_t response;
            r = initnatpmp(&natpmp, 0, 0);],
            [printf("initnatpmp() returned %d (%s)\n", r, r?"FAILED":"SUCCESS");
            exit(0);],
        [--with-libnatpmp-dir],
        [/usr/lib/])
fi


dnl ------------------------------------------------------
dnl Where do you live, libminiupnpc?  And how do we call you?
dnl There are no packages for Debian or Redhat as of this patch

if test "$upnp" = "true"; then
    AC_DEFINE(MINIUPNPC, 1, [Define to 1 if we are building with UPnP.])

    dnl Before we call TOR_SEARCH_LIBRARY we'll do a quick compile test
    dnl to see if we have miniupnpc-1.5 or -1.6
    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <miniupnpc/miniupnpc.h>],
        [upnpDiscover(1, 0, 0, 0);exit(0);])],[miniupnpc15="true"],[miniupnpc15="false"])

    if test "$miniupnpc15" = "true" ; then
        AC_DEFINE([MINIUPNPC15],[1],[libminiupnpc version 1.5 found])
        TOR_SEARCH_LIBRARY(libminiupnpc, $trylibminiupnpcdir, [-lminiupnpc $TOR_LIB_WS32 $TOR_LIB_IPHLPAPI],
            [#include <miniupnpc/miniwget.h>
             #include <miniupnpc/miniupnpc.h>
             #include <miniupnpc/upnpcommands.h>],
            [void upnpDiscover(int delay, const char * multicastif,
             const char * minissdpdsock, int sameport);],
            [upnpDiscover(1, 0, 0, 0); exit(0);],
            [--with-libminiupnpc-dir],
            [/usr/lib/])
    else
        TOR_SEARCH_LIBRARY(libminiupnpc, $trylibminiupnpcdir, [-lminiupnpc $TOR_LIB_WS32 $TOR_LIB_IPHLPAPI],
            [#include <miniupnpc/miniwget.h>
             #include <miniupnpc/miniupnpc.h>
             #include <miniupnpc/upnpcommands.h>],
            [void upnpDiscover(int delay, const char * multicastif,
             const char * minissdpdsock, int sameport, int ipv6, int * error);],
            [upnpDiscover(1, 0, 0, 0, 0, 0); exit(0);],
            [--with-libminiupnpc-dir],
            [/usr/lib/])
    fi
fi

dnl Make sure to enable support for large off_t if available.
AC_SYS_LARGEFILE

AC_CHECK_HEADERS(
        assert.h \
        errno.h \
        fcntl.h \
        signal.h \
        string.h \
        sys/fcntl.h \
        sys/stat.h \
        sys/time.h \
        sys/types.h \
        time.h \
        unistd.h
 , , AC_MSG_WARN(Some headers were not found, compilation may fail.  If compilation succeeds, please send your orconfig.h to the developers so we can fix this warning.))

dnl These headers are not essential

AC_CHECK_HEADERS(
        arpa/inet.h \
        crt_externs.h \
        grp.h \
        ifaddrs.h \
        inttypes.h \
        limits.h \
        linux/types.h \
        machine/limits.h \
        malloc.h \
        malloc/malloc.h \
        malloc_np.h \
        netdb.h \
        netinet/in.h \
        netinet/in6.h \
        pwd.h \
        stdint.h \
        sys/file.h \
        sys/ioctl.h \
        sys/limits.h \
        sys/mman.h \
        sys/param.h \
        sys/prctl.h \
        sys/resource.h \
        sys/socket.h \
        sys/syslimits.h \
        sys/time.h \
        sys/types.h \
        sys/un.h \
        sys/utime.h \
        sys/wait.h \
        syslog.h \
        utime.h
)

AC_CHECK_HEADERS(sys/param.h)

TOR_CHECK_PROTOTYPE(malloc_good_size, HAVE_MALLOC_GOOD_SIZE_PROTOTYPE,
[#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif
#ifdef HAVE_MALLOC_MALLOC_H
#include <malloc/malloc.h>
#endif])

AC_CHECK_HEADERS(net/if.h, net_if_found=1, net_if_found=0,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif])
AC_CHECK_HEADERS(net/pfvar.h, net_pfvar_found=1, net_pfvar_found=0,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_NET_IF_H
#include <net/if.h>
#endif])
AC_CHECK_HEADERS(linux/netfilter_ipv4.h,
        linux_netfilter_ipv4=1, linux_netfilter_ipv4=0,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif
#ifdef HAVE_LINUX_TYPES_H
#include <linux/types.h>
#endif
#ifdef HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif])

if test x$transparent = xtrue ; then
   transparent_ok=0
   if test x$net_if_found = x1 && test x$net_pfvar_found = x1 ; then
     transparent_ok=1
   fi
   if test x$linux_netfilter_ipv4 = x1 ; then
     transparent_ok=1
   fi
   if test x$transparent_ok = x1 ; then
     AC_DEFINE(USE_TRANSPARENT, 1, "Define to enable transparent proxy support")
     case $host in
       *-*-openbsd*)
         AC_DEFINE(OPENBSD, 1, "Define to handle pf on OpenBSD properly") ;;
     esac
   else
     AC_MSG_NOTICE([Transparent proxy support enabled, but missing headers.])
   fi
fi

AC_CHECK_MEMBERS([struct timeval.tv_sec], , ,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif])

dnl In case we aren't given a working stdint.h, we'll need to grow our own.
dnl Watch out.

AC_CHECK_SIZEOF(int8_t)
AC_CHECK_SIZEOF(int16_t)
AC_CHECK_SIZEOF(int32_t)
AC_CHECK_SIZEOF(int64_t)
AC_CHECK_SIZEOF(uint8_t)
AC_CHECK_SIZEOF(uint16_t)
AC_CHECK_SIZEOF(uint32_t)
AC_CHECK_SIZEOF(uint64_t)
AC_CHECK_SIZEOF(intptr_t)
AC_CHECK_SIZEOF(uintptr_t)

dnl AC_CHECK_TYPES([int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t, uint32_t, uint64_t, intptr_t, uintptr_t])

AC_CHECK_SIZEOF(char)
AC_CHECK_SIZEOF(short)
AC_CHECK_SIZEOF(int)
AC_CHECK_SIZEOF(long)
AC_CHECK_SIZEOF(long long)
AC_CHECK_SIZEOF(__int64)
AC_CHECK_SIZEOF(void *)
AC_CHECK_SIZEOF(time_t)
AC_CHECK_SIZEOF(size_t)

AC_CHECK_TYPES([uint, u_char, ssize_t])

dnl used to include sockaddr_storage, but everybody has that.
AC_CHECK_TYPES([struct in6_addr, struct sockaddr_in6, sa_family_t], , ,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef _WIN32
#define _WIN32_WINNT 0x0501
#define WIN32_LEAN_AND_MEAN
#if defined(_MSC_VER) && (_MSC_VER < 1300)
#include <winsock.h>
#else
#include <winsock2.h>
#include <ws2tcpip.h>
#endif
#endif
])
AC_CHECK_MEMBERS([struct in6_addr.s6_addr32, struct in6_addr.s6_addr16, struct sockaddr_in.sin_len, struct sockaddr_in6.sin6_len], , ,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef _WIN32
#define _WIN32_WINNT 0x0501
#define WIN32_LEAN_AND_MEAN
#if defined(_MSC_VER) && (_MSC_VER < 1300)
#include <winsock.h>
#else
#include <winsock2.h>
#include <ws2tcpip.h>
#endif
#endif
])

AC_CHECK_TYPES([rlim_t], , ,
[#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
])

AC_CACHE_CHECK([whether time_t is signed], tor_cv_time_t_signed, [
AC_RUN_IFELSE([AC_LANG_SOURCE([
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_TIME_H
#include <time.h>
#endif
int main(int c, char**v) { if (((time_t)-1)<0) return 1; else return 0; }])],
  tor_cv_time_t_signed=no, tor_cv_time_t_signed=yes, tor_cv_time_t_signed=cross)
])

if test "$tor_cv_time_t_signed" = cross; then
  AC_MSG_NOTICE([Cross compiling: assuming that time_t is signed.])
fi

if test "$tor_cv_time_t_signed" != no; then
  AC_DEFINE([TIME_T_IS_SIGNED], 1,
            [Define to 1 iff time_t is signed])
fi

AC_CACHE_CHECK([whether size_t is signed], tor_cv_size_t_signed, [
AC_RUN_IFELSE([AC_LANG_SOURCE([
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
int main(int c, char**v) { if (((size_t)-1)<0) return 1; else return 0; }])],
  tor_cv_size_t_signed=no, tor_cv_size_t_signed=yes, tor_cv_size_t_signed=cross)
])

if test "$tor_cv_size_t_signed" = cross; then
  AC_MSG_NOTICE([Cross compiling: assuming that size_t is not signed.])
fi

if test "$tor_cv_size_t_signed" = yes; then
  AC_MSG_ERROR([You have a signed size_t; that's grossly nonconformant.])
fi

AC_CHECK_SIZEOF(socklen_t, , [AC_INCLUDES_DEFAULT()
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
])

# We want to make sure that we _don't_ have a cell_t defined, like IRIX does.

AC_CHECK_SIZEOF(cell_t)

# Now make sure that NULL can be represented as zero bytes.
AC_CACHE_CHECK([whether memset(0) sets pointers to NULL], tor_cv_null_is_zero,
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[[#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#ifdef HAVE_STDDEF_H
#include <stddef.h>
#endif
int main () { char *p1,*p2; p1=NULL; memset(&p2,0,sizeof(p2));
return memcmp(&p1,&p2,sizeof(char*))?1:0; }]])],
       [tor_cv_null_is_zero=yes],
       [tor_cv_null_is_zero=no],
       [tor_cv_null_is_zero=cross])])

if test "$tor_cv_null_is_zero" = cross ; then
  # Cross-compiling; let's hope that the target isn't raving mad.
  AC_MSG_NOTICE([Cross-compiling: we'll assume that NULL is represented as a sequence of 0-valued bytes.])
fi

if test "$tor_cv_null_is_zero" != no; then
  AC_DEFINE([NULL_REP_IS_ZERO_BYTES], 1,
            [Define to 1 iff memset(0) sets pointers to NULL])
fi

# And what happens when we malloc zero?
AC_CACHE_CHECK([whether we can malloc(0) safely.], tor_cv_malloc_zero_works,
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[[#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#ifdef HAVE_STDDEF_H
#include <stddef.h>
#endif
int main () { return malloc(0)?0:1; }]])],
       [tor_cv_malloc_zero_works=yes],
       [tor_cv_malloc_zero_works=no],
       [tor_cv_malloc_zero_works=cross])])

if test "$tor_cv_malloc_zero_works" = cross; then
  # Cross-compiling; let's hope that the target isn't raving mad.
  AC_MSG_NOTICE([Cross-compiling: we'll assume that we need to check malloc() arguments for 0.])
fi

if test "$tor_cv_malloc_zero_works" = yes; then
  AC_DEFINE([MALLOC_ZERO_WORKS], 1,
            [Define to 1 iff malloc(0) returns a pointer])
fi

# whether we seem to be in a 2s-complement world.
AC_CACHE_CHECK([whether we are using 2s-complement arithmetic], tor_cv_twos_complement,
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[[int main () { int problem = ((-99) != (~99)+1);
return problem ? 1 : 0; }]])],
       [tor_cv_twos_complement=yes],
       [tor_cv_twos_complement=no],
       [tor_cv_twos_complement=cross])])

if test "$tor_cv_twos_complement" = cross ; then
  # Cross-compiling; let's hope that the target isn't raving mad.
  AC_MSG_NOTICE([Cross-compiling: we'll assume that negative integers are represented with two's complement.])
fi

if test "$tor_cv_twos_complement" != no ; then
  AC_DEFINE([USING_TWOS_COMPLEMENT], 1,
            [Define to 1 iff we represent negative integers with two's complement])
fi

# What does shifting a negative value do?
AC_CACHE_CHECK([whether right-shift on negative values does sign-extension], tor_cv_sign_extend,
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[[int main () { int okay = (-60 >> 8) == -1; return okay ? 0 : 1; }]])],
       [tor_cv_sign_extend=yes],
       [tor_cv_sign_extend=no],
       [tor_cv_sign_extend=cross])])

if test "$tor_cv_sign_extend" = cross ; then
  # Cross-compiling; let's hope that the target isn't raving mad.
  AC_MSG_NOTICE([Cross-compiling: we'll assume that right-shifting negative integers causes sign-extension])
fi

if test "$tor_cv_sign_extend" != no ; then
  AC_DEFINE([RSHIFT_DOES_SIGN_EXTEND], 1,
            [Define to 1 iff right-shifting a negative value performs sign-extension])
fi

# Whether we should use the dmalloc memory allocation debugging library.
AC_MSG_CHECKING(whether to use dmalloc (debug memory allocation library))
AC_ARG_WITH(dmalloc,
[  --with-dmalloc          Use debug memory allocation library. ],
[if [[ "$withval" = "yes" ]]; then
  dmalloc=1
  AC_MSG_RESULT(yes)
else
  dmalloc=1
  AC_MSG_RESULT(no)
fi], [ dmalloc=0; AC_MSG_RESULT(no) ]
)

if [[ $dmalloc -eq 1 ]]; then
  AC_CHECK_HEADERS(dmalloc.h, , AC_MSG_ERROR(dmalloc header file not found. Do you have the development files for dmalloc installed?))
  AC_SEARCH_LIBS(dmalloc_malloc, [dmallocth dmalloc], , AC_MSG_ERROR(Libdmalloc library not found. If you enable it you better have it installed.))
  AC_DEFINE(USE_DMALLOC, 1, [Debug memory allocation library])
  AC_DEFINE(DMALLOC_FUNC_CHECK, 1, [Enable dmalloc's malloc function check])
  AC_CHECK_FUNCS(dmalloc_strdup dmalloc_strndup)
fi

AC_ARG_WITH(tcmalloc,
[  --with-tcmalloc         Use tcmalloc memory allocation library. ],
[ tcmalloc=yes ], [ tcmalloc=no ])

if test x$tcmalloc = xyes ; then
   LDFLAGS="-ltcmalloc $LDFLAGS"
fi

# By default, we're going to assume we don't have mlockall()
# bionic and other platforms have various broken mlockall subsystems.
# Some systems don't have a working mlockall, some aren't linkable,
# and some have it but don't declare it.
AC_CHECK_FUNCS(mlockall)
AC_CHECK_DECLS([mlockall], , , [
#ifdef HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif])

# Allow user to specify an alternate syslog facility
AC_ARG_WITH(syslog-facility,
[  --with-syslog-facility=LOG syslog facility to use (default=LOG_DAEMON)],
syslog_facility="$withval", syslog_facility="LOG_DAEMON")
AC_DEFINE_UNQUOTED(LOGFACILITY,$syslog_facility,[name of the syslog facility])
AC_SUBST(LOGFACILITY)

# Check if we have getresuid and getresgid
AC_CHECK_FUNCS(getresuid getresgid)

# Check for gethostbyname_r in all its glorious incompatible versions.
#   (This logic is based on that in Python's configure.in)
AH_TEMPLATE(HAVE_GETHOSTBYNAME_R,
  [Define this if you have any gethostbyname_r()])

AC_CHECK_FUNC(gethostbyname_r, [
  AC_MSG_CHECKING([how many arguments gethostbyname_r() wants])
  OLD_CFLAGS=$CFLAGS
  CFLAGS="$CFLAGS $MY_CPPFLAGS $MY_THREAD_CPPFLAGS $MY_CFLAGS"
  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([
#include <netdb.h>
  ], [[
    char *cp1, *cp2;
    struct hostent *h1, *h2;
    int i1, i2;
    (void)gethostbyname_r(cp1,h1,cp2,i1,&h2,&i2);
  ]])],[
    AC_DEFINE(HAVE_GETHOSTBYNAME_R)
    AC_DEFINE(HAVE_GETHOSTBYNAME_R_6_ARG, 1,
     [Define this if gethostbyname_r takes 6 arguments])
    AC_MSG_RESULT(6)
  ], [
    AC_TRY_COMPILE([
#include <netdb.h>
    ], [
      char *cp1, *cp2;
      struct hostent *h1;
      int i1, i2;
      (void)gethostbyname_r(cp1,h1,cp2,i1,&i2);
    ], [
      AC_DEFINE(HAVE_GETHOSTBYNAME_R)
      AC_DEFINE(HAVE_GETHOSTBYNAME_R_5_ARG, 1,
        [Define this if gethostbyname_r takes 5 arguments])
      AC_MSG_RESULT(5)
   ], [
      AC_TRY_COMPILE([
#include <netdb.h>
     ], [
       char *cp1;
       struct hostent *h1;
       struct hostent_data hd;
       (void) gethostbyname_r(cp1,h1,&hd);
     ], [
       AC_DEFINE(HAVE_GETHOSTBYNAME_R)
       AC_DEFINE(HAVE_GETHOSTBYNAME_R_3_ARG, 1,
         [Define this if gethostbyname_r takes 3 arguments])
       AC_MSG_RESULT(3)
     ], [
       AC_MSG_RESULT(0)
     ])
  ])
 ])
 CFLAGS=$OLD_CFLAGS
])

AC_CACHE_CHECK([whether the C compiler supports __func__],
  tor_cv_have_func_macro,
  AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <stdio.h>
int main(int c, char **v) { puts(__func__); }])],
  tor_cv_have_func_macro=yes,
  tor_cv_have_func_macro=no))

AC_CACHE_CHECK([whether the C compiler supports __FUNC__],
  tor_cv_have_FUNC_macro,
  AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <stdio.h>
int main(int c, char **v) { puts(__FUNC__); }])],
  tor_cv_have_FUNC_macro=yes,
  tor_cv_have_FUNC_macro=no))

AC_CACHE_CHECK([whether the C compiler supports __FUNCTION__],
  tor_cv_have_FUNCTION_macro,
  AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <stdio.h>
int main(int c, char **v) { puts(__FUNCTION__); }])],
  tor_cv_have_FUNCTION_macro=yes,
  tor_cv_have_FUNCTION_macro=no))

AC_CACHE_CHECK([whether we have extern char **environ already declared],
  tor_cv_have_environ_declared,
  AC_COMPILE_IFELSE([AC_LANG_SOURCE([
/* We define _GNU_SOURCE here because it is also defined in compat.c.
 * Without it environ doesn't get declared. */
#define _GNU_SOURCE
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <stdlib.h>
int main(int c, char **v) { char **t = environ; }])],
  tor_cv_have_environ_declared=yes,
  tor_cv_have_environ_declared=no))

if test "$tor_cv_have_func_macro" = 'yes'; then
  AC_DEFINE(HAVE_MACRO__func__, 1, [Defined if the compiler supports __func__])
fi

if test "$tor_cv_have_FUNC_macro" = 'yes'; then
  AC_DEFINE(HAVE_MACRO__FUNC__, 1, [Defined if the compiler supports __FUNC__])
fi

if test "$tor_cv_have_FUNCTION_macro" = 'yes'; then
  AC_DEFINE(HAVE_MACRO__FUNCTION__, 1,
           [Defined if the compiler supports __FUNCTION__])
fi

if test "$tor_cv_have_environ_declared" = 'yes'; then
  AC_DEFINE(HAVE_EXTERN_ENVIRON_DECLARED, 1,
           [Defined if we have extern char **environ already declared])
fi

# $prefix stores the value of the --prefix command line option, or
# NONE if the option wasn't set.  In the case that it wasn't set, make
# it be the default, so that we can use it to expand directories now.
if test "x$prefix" = "xNONE"; then
  prefix=$ac_default_prefix
fi

# and similarly for $exec_prefix
if test "x$exec_prefix" = "xNONE"; then
  exec_prefix=$prefix
fi

if test "x$BUILDDIR" = "x"; then
  BUILDDIR=`pwd`
fi
AC_SUBST(BUILDDIR)
AH_TEMPLATE([BUILDDIR],[tor's build directory])
AC_DEFINE_UNQUOTED(BUILDDIR,"$BUILDDIR")

if test "x$CONFDIR" = "x"; then
  CONFDIR=`eval echo $sysconfdir/tor`
fi
AC_SUBST(CONFDIR)
AH_TEMPLATE([CONFDIR],[tor's configuration directory])
AC_DEFINE_UNQUOTED(CONFDIR,"$CONFDIR")

BINDIR=`eval echo $bindir`
AC_SUBST(BINDIR)
LOCALSTATEDIR=`eval echo $localstatedir`
AC_SUBST(LOCALSTATEDIR)

if test "$bwin32" = true; then
  # Test if the linker supports the --nxcompat and --dynamicbase options
  # for Windows
  save_LDFLAGS="$LDFLAGS"
  LDFLAGS="-Wl,--nxcompat -Wl,--dynamicbase"
  AC_MSG_CHECKING([whether the linker supports DllCharacteristics])
  AC_LINK_IFELSE([AC_LANG_PROGRAM([])],
    [AC_MSG_RESULT([yes])]
    [save_LDFLAGS="$save_LDFLAGS $LDFLAGS"],
    [AC_MSG_RESULT([no])]
  )
  LDFLAGS="$save_LDFLAGS"
fi

# Set CFLAGS _after_ all the above checks, since our warnings are stricter
# than autoconf's macros like.
if test "$GCC" = yes; then
  # Disable GCC's strict aliasing checks.  They are an hours-to-debug
  # accident waiting to happen.
  CFLAGS="$CFLAGS -Wall -fno-strict-aliasing"
else
  # Autoconf sets -g -O2 by default. Override optimization level
  # for non-gcc compilers
  CFLAGS="$CFLAGS -O"
  enable_gcc_warnings=no
  enable_gcc_warnings_advisory=no
fi

# OS X Lion started deprecating the system openssl. Let's just disable
# all deprecation warnings on OS X. Also, to potentially make the binary
# a little smaller, let's enable dead_strip.
case "$host_os" in

 darwin*)
    CFLAGS="$CFLAGS -Wno-deprecated-declarations"
    LDFLAGS="$LDFLAGS -dead_strip" ;;
esac

# Add some more warnings which we use in development but not in the
# released versions.  (Some relevant gcc versions can't handle these.)
if test x$enable_gcc_warnings = xyes || test x$enable_gcc_warnings_advisory = xyes; then

  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
#if !defined(__GNUC__) || (__GNUC__ < 4)
#error
#endif])], have_gcc4=yes, have_gcc4=no)

  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
#if !defined(__GNUC__) || (__GNUC__ < 4) || (__GNUC__ == 4 && __GNUC_MINOR__ < 2)
#error
#endif])], have_gcc42=yes, have_gcc42=no)

  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
#if !defined(__GNUC__) || (__GNUC__ < 4) || (__GNUC__ == 4 && __GNUC_MINOR__ < 3)
#error
#endif])], have_gcc43=yes, have_gcc43=no)

  save_CFLAGS="$CFLAGS"
  CFLAGS="$CFLAGS -Wshorten-64-to-32"
  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], have_shorten64_flag=yes,
                    have_shorten64_flag=no)
  CFLAGS="$save_CFLAGS"

  case $host in
    *-*-openbsd*)
      # Some OpenBSD versions (like 4.8) have -Wsystem-headers by default.
      # That's fine, except that the headers don't pass -Wredundant-decls.
      # Therefore, let's disable -Wsystem-headers when we're building
      # with maximal warnings on OpenBSD.
      CFLAGS="$CFLAGS -Wno-system-headers" ;;
  esac