diff --git a/src/core/charutil.cpp b/src/core/charutil.cpp
index 78cab49..1bfea90 100644
--- a/src/core/charutil.cpp
+++ b/src/core/charutil.cpp
@@ -90,7 +90,7 @@ bool cCharUtil::PeekNextChar(  const TSTRING::const_iterator& cur,
     }   
     else
     {
-#ifndef __AROS__
+#if !IS_AROS
     mblen (NULL, 0);
     int len = mblen(&*cur, MB_CUR_MAX);
     if (len < 0) //invalid multibyte sequence, but let's not blow up.
diff --git a/src/core/codeconvert.cpp b/src/core/codeconvert.cpp
index 1ffd4c5..07d40f2 100755
--- a/src/core/codeconvert.cpp
+++ b/src/core/codeconvert.cpp
@@ -61,7 +61,7 @@
 #define TSS_USE_UCS2_CCONV16        (!(HAVE_ICONV_H) && WCHAR_REP_IS_UCS2 && WCHAR_IS_16_BITS)
 #define TSS_USE_UCS2_CCONV32        (!(HAVE_ICONV_H) && WCHAR_REP_IS_UCS2 && WCHAR_IS_32_BITS)
 
-#ifdef __minix__
+#if ICONV_CONST_SOURCE
 # define ICONV_SOURCE_TYPE const char
 #else
 # define ICONV_SOURCE_TYPE char
diff --git a/src/core/file.h b/src/core/file.h
index 1889c9f..a98f099 100644
--- a/src/core/file.h
+++ b/src/core/file.h
@@ -47,7 +47,7 @@
 #include "fileerror.h"
 #endif
 
-#ifdef __MINT__ // for off_t
+#if IS_MINT // for off_t
 #include <sys/types.h>
 #endif
 
@@ -143,7 +143,7 @@ public:
 };
 
 
-#ifdef __AROS__
+#if IS_AROS
 class cArosPath
 {
 public:
diff --git a/src/core/file_unix.cpp b/src/core/file_unix.cpp
index 4c22b45..6a9225d 100644
--- a/src/core/file_unix.cpp
+++ b/src/core/file_unix.cpp
@@ -34,7 +34,7 @@
 
 /* On GNU/Hurd, need to define _GNU_SOURCE in order to use  O_NOATIME
    which technically is still a nonstandard extension to open() */
-#ifdef __gnu_hurd__
+#if IS_HURD
 # define _GNU_SOURCE
 #endif
 
@@ -53,7 +53,7 @@
 #include <fcntl.h>
 #include <errno.h>
 
-#ifdef __hpux__
+#if IS_HPUX
 # include <sys/fs/vx_ioctl.h>
 #endif
 
@@ -104,7 +104,7 @@ cFile_i::~cFile_i()
         fclose( mpCurrStream );
     mpCurrStream = NULL;
 
-#ifdef __AROS__
+#if IS_AROS
     if( mFlags & cFile::OPEN_LOCKED_TEMP )
     {
         // unlink this file 
@@ -219,7 +219,7 @@ void cFile::Open( const TSTRING& sFileNameC, uint32 flags )
         throw( eFileOpen( sFileName, iFSServices::GetInstance()->GetErrString() ) );
     }
 
-#ifndef __AROS__
+#if !IS_AROS
     if( flags & OPEN_LOCKED_TEMP )
     {
         // unlink this file 
@@ -246,13 +246,11 @@ void cFile::Open( const TSTRING& sFileNameC, uint32 flags )
         fcntl(fh, F_NOCACHE, 1);
 #endif   
 
-#ifdef __sun
+#if IS_SOLARIS
     if ((flags & OPEN_DIRECT) && (flags & OPEN_SCANNING))
         directio(fh, DIRECTIO_ON);
-#endif
-
-#ifdef __hpux__
-
+    
+#elif IS_HPUX
     if (flags & OPEN_SCANNING) 
     {
         if (flags & OPEN_DIRECT)
@@ -460,7 +458,7 @@ void cFile::Truncate( File_t offset ) // throw(eFile)
 }
 
 
-#ifdef __AROS__
+#if IS_AROS
 TSTRING cArosPath::AsPosix( const TSTRING& in )
 {
     if (in[0] == '/')
diff --git a/src/core/msystem.cpp b/src/core/msystem.cpp
index c0158e4..09a2653 100644
--- a/src/core/msystem.cpp
+++ b/src/core/msystem.cpp
@@ -74,7 +74,7 @@
 #include "config.h"
 #include <stdio.h>
 #include <sys/types.h>
-#ifndef _SORTIX_SOURCE
+#if !IS_SORTIX
 # include <sys/file.h>
 #endif
 #include <sys/stat.h>
@@ -871,7 +871,7 @@ FILE *fp[];
         return(mfpclose(indx, fp));
 }
 
-#ifdef __AROS__
+#if IS_AROS
  #define fork() vfork()
 #endif
 
diff --git a/src/core/msystem.h b/src/core/msystem.h
index 09aee38..9f0a13e 100644
--- a/src/core/msystem.h
+++ b/src/core/msystem.h
@@ -54,6 +54,9 @@
 /*
  * forward declarations
  */
+
+#include "platform.h"
+
 #ifdef __STDC__
 void le_clobber(void);
 int le_set(const char*);
@@ -114,7 +117,7 @@ int echild();
 #   define GID_RESET    -2      /* reset EGID to RGID */
 #endif
 #ifndef DEF_PATH
-#   ifdef __FreeBSD_cc_version
+#   if IS_FREEBSD
 #       define DEF_PATH "PATH=/sbin:/usr/sbin:/bin:/usr/bin"  /* default search path */
 #   else
 #       define DEF_PATH "PATH=/bin:/usr/bin:/usr/ucb"   /* default search path */
diff --git a/src/core/platform.h b/src/core/platform.h
index 61284a0..29d229c 100644
--- a/src/core/platform.h
+++ b/src/core/platform.h
@@ -64,7 +64,6 @@
 #define OS_DARWIN       0x0304
 #define OS_DRAGONFLYBSD 0x0305
 #define OS_MIDNIGHTBSD  0x0306
-#define OS_HARDENEDBSD  0x0307
 
 #define OS_SOLARIS      0x0400
 #define OS_AIX          0x0401
@@ -137,14 +136,28 @@
     #define OS                  OS_FREEBSD
     #define IS_FREEBSD          1	
 
-// add NetBSD, OpenBSD, other BSDs	
-	
+#elif defined(__NetBSD__)
+    #define OS                  OS_NETBSD
+    #define IS_NETBSD           1
+
+#elif defined(__OpenBSD__)
+    #define OS                  OS_OPENBSD
+    #define IS_OPENBSD          1
+
 #elif defined(_OSX)
     #define OS                  OS_DARWIN
     #define IS_DARWIN           1	
-	
 
-#elif defined(_SOLARIS)
+#elif defined(__DragonFly__)
+    #define OS                  OS_DRAGONFLYBSD
+    #define IS_DRAGONFLYBSD     1
+
+#elif defined(__MidnightBSD__)
+    #define OS                  OS_MIDNIGHTBSD
+    #define IS_MIDNIGHTBSD      1
+
+
+#elif defined(_SOLARIS) || defined(__sun)
     #define OS					OS_SOLARIS
     #define IS_SOLARIS          1	
 	
@@ -164,13 +177,19 @@
     #define OS                  OS_OSF1
     #define IS_OSF1             1
 	
-	
-// need Minix, Haiku	
-	
+
+#elif defined(__minix__)
+    #define OS					OS_MINIX
+    #define IS_MINIX			1
+
 #elif defined(__gnu_hurd__)
     #define OS					OS_HURD
 	#define IS_HURD				1 
-	
+
+#elif defined(__HAIKU__)
+    #define OS                  OS_HAIKU
+    #define IS_HAIKU            1
+
 #elif defined(__SYLLABLE__)
     #define OS                  OS_SYLLABLE
     #define IS_SYLLABLE         1	
@@ -274,6 +293,16 @@
 #define SUPPORTS_MEMBER_TEMPLATES               ( ! IS_SUNPRO )
 #define SUPPORTS_EXPLICIT_TEMPLATE_FUNC_INST    ( ! IS_SUNPRO )
 
+#define SUPPORTS_ST_BLOCKS          (!IS_DOS_DJGPP)
+#define SUPPORTS_POSIX_SIGNALS      (!IS_DOS_DJGPP)
+#define SUPPORTS_NETWORKING         (!IS_SORTIX && !IS_DOS_DJGPP)
+#define SUPPORTS_SYSLOG             (HAVE_SYSLOG_H && !IS_SKYOS)
+#define NEEDS_SWAB_IMPL             (IS_SYLLABLE || IS_ANDROID || IS_SORTIX)
+#define USES_MBLEN                  (!IS_ANDROID && !IS_AROS)
+#define ICONV_CONST_SOURCE          (IS_MINIX)
+
+
+
 //=============================================================================
 // Miscellaneous
 //
diff --git a/src/core/stringutil.cpp b/src/core/stringutil.cpp
index 3663d03..bb3fecc 100644
--- a/src/core/stringutil.cpp
+++ b/src/core/stringutil.cpp
@@ -137,7 +137,7 @@ inline bool tss_find_in_hash( const wc16_string& lhs, TSTRING& rhs )
 std::string::const_iterator
 cStringUtil::Convert( std::string& nbs, const wc16_string& dbs )
 {
-#ifdef __AROS__
+#if IS_AROS
     nbs.resize(dbs.length());
     for (int x=0; x<dbs.length(); ++x)
         nbs[x] = (unsigned char)dbs[x];
@@ -192,7 +192,7 @@ cStringUtil::Convert( std::string& nbs, const wc16_string& dbs )
 wc16_string::const_iterator
 cStringUtil::Convert( wc16_string& dbs, const std::string& nbs )
 {
-#ifdef __AROS__
+#if IS_AROS
     dbs.resize(nbs.length());
     for (int x=0; x<nbs.length(); x++)
        dbs[x] = (unsigned short)nbs[x];
diff --git a/src/core/timeconvert.cpp b/src/core/timeconvert.cpp
index 2cece24..e7b73da 100644
--- a/src/core/timeconvert.cpp
+++ b/src/core/timeconvert.cpp
@@ -54,7 +54,7 @@
 
 #define TIME_MAX    2147483647L // largest signed 32 bit number
 
-#ifdef __AROS__
+#if IS_AROS
  #define tzset()
 #endif
 
diff --git a/src/core/twlocale.cpp b/src/core/twlocale.cpp
index ada1b25..bf85ea9 100644
--- a/src/core/twlocale.cpp
+++ b/src/core/twlocale.cpp
@@ -68,7 +68,7 @@ static TSTRING& util_FormatTimeCPlusPlus( struct tm* ptm, TSTRING& strBuf );
 // PUBLIC METHOD CODE
 //=========================================================================
 
-#ifdef __AROS__
+#if IS_AROS
   #define tzset()
 #endif
 
diff --git a/src/core/unixfsservices.cpp b/src/core/unixfsservices.cpp
index ac7ed07..f160f28 100644
--- a/src/core/unixfsservices.cpp
+++ b/src/core/unixfsservices.cpp
@@ -178,7 +178,7 @@ TCHAR  cUnixFSServices::GetPathSeparator() const
     return '/';
 }
 
-#ifndef __AROS__
+#if !IS_AROS
 void cUnixFSServices::ReadDir(const TSTRING& strFilename, std::vector<TSTRING> &v, bool bFullPaths) const throw(eFSServices)
 {
 #else
@@ -326,7 +326,7 @@ void cUnixFSServices::SetTempDirName(TSTRING& tmpPath) {
 }
 
 
-#ifndef __AROS__
+#if !IS_AROS
 void cUnixFSServices::Stat( const TSTRING& strName, cFSStatArgs &stat ) const throw(eFSServices)
 {
 #else
@@ -369,7 +369,7 @@ void cUnixFSServices::Stat( const TSTRING& strNameC, cFSStatArgs& stat) const th
     stat.size       = statbuf.st_size;
     stat.uid        = statbuf.st_uid;
     stat.blksize    = statbuf.st_blksize;
-#ifndef __DJGPP__
+#if SUPPORTS_ST_BLOCKS
     stat.blocks     = statbuf.st_blocks;
 #else
     stat.blocks     = 0;
@@ -409,7 +409,7 @@ void cUnixFSServices::GetMachineNameFullyQualified( TSTRING& strName ) const
     char buf[256];
     if (gethostname(buf, 256) != 0)
     {
-#if defined(SOLARIS_NO_GETHOSTBYNAME) || defined(_SORTIX_SOURCE) || defined(__DJGPP__)
+#if defined(SOLARIS_NO_GETHOSTBYNAME) || !SUPPORTS_NETWORKING
         strName = buf;
         return;
 #else
@@ -464,7 +464,7 @@ bool cUnixFSServices::GetIPAddress( uint32& uiIPAddress )
     bool    fGotAddress = false;    
     cDebug  d( _T("cUnixFSServices::GetIPAddress") );
 
-#if !defined(_SORTIX_SOURCE) && !defined(__DJGPP__)
+#if SUPPORTS_NETWORKING
     struct utsname utsnameBuf;    
     if( EFAULT != uname( &utsnameBuf) )
     {
diff --git a/src/cryptlib/misc.h b/src/cryptlib/misc.h
index 95a4711..664d993 100644
--- a/src/cryptlib/misc.h
+++ b/src/cryptlib/misc.h
@@ -9,7 +9,7 @@
  #include <string.h>
 #endif
 
-#if defined(__MINT__) || defined(__MSDOS__) // has memory.h, but memset defined in string.h anyway.
+#if IS_MINT || IS_DOS_DJGPP // has memory.h, but memset defined in string.h anyway.
  #include <string.h>
 #endif
 
diff --git a/src/fs/fsparserutil.cpp b/src/fs/fsparserutil.cpp
index e4f6979..5ca28ea 100644
--- a/src/fs/fsparserutil.cpp
+++ b/src/fs/fsparserutil.cpp
@@ -137,7 +137,7 @@ void cFSParserUtil::InterpretFCOName( const std::list<TSTRING>& l, cFCOName& nam
     for( std::list<TSTRING>::const_iterator i = l.begin(); i != l.end(); i++ )
         strT += *i;
 
-#ifdef __AROS__
+#if IS_AROS
     strT = cArosPath::AsPosix(strT);
 #endif
 
diff --git a/src/siggen/siggenstrings.cpp b/src/siggen/siggenstrings.cpp
index d627a24..fb8a8c2 100644
--- a/src/siggen/siggenstrings.cpp
+++ b/src/siggen/siggenstrings.cpp
@@ -42,7 +42,7 @@
 #include "stdsiggen.h"
 #include "siggenstrings.h"
 
-#ifdef __AROS__
+#if IS_AROS
 # define VERSION_PREFIX "$VER: "
 #else
 # define VERSION_PREFIX "@(#)"
diff --git a/src/tripwire/smtpmailmessage.cpp b/src/tripwire/smtpmailmessage.cpp
index a16a20b..472b098 100644
--- a/src/tripwire/smtpmailmessage.cpp
+++ b/src/tripwire/smtpmailmessage.cpp
@@ -56,7 +56,7 @@
 #include <sys/time.h>
 #include <sys/utsname.h>
 
-#ifdef _SORTIX_SOURCE
+#if !IS_SORTIX
 # include <sys/select.h>
 #endif
 
@@ -72,7 +72,7 @@
 
 #define INVALID_SOCKET -1
 
-#ifdef __AROS__
+#if IS_AROS
  #ifndef HAVE_GETHOSTNAME
   #define HAVE_GETHOSTNAME 1
  #endif
@@ -177,7 +177,7 @@ long cSMTPMailMessage::GetServerAddress()
     }
     else
     {
-#if defined(_SORTIX_SOURCE) || !defined(HAVE_SYS_SOCKET_H)
+#if IS_SORTIX || !defined(HAVE_SYS_SOCKET_H)
         return INADDR_NONE;
 #else
         // do a DNS lookup of the hostname and get the long
diff --git a/src/tripwire/syslog_trip.cpp b/src/tripwire/syslog_trip.cpp
index c178e6b..66da277 100644
--- a/src/tripwire/syslog_trip.cpp
+++ b/src/tripwire/syslog_trip.cpp
@@ -49,7 +49,7 @@
 #include "tw/twerrors.h"
 #include "tw/twstrings.h"
 
-#ifdef __AROS__
+#if IS_AROS
   #include <proto/bsdsocket.h>
   #define openlog(a,b,c)
   #define closelog()
@@ -60,8 +60,9 @@
 ///////////////////////////////////////////////////////////////////////////////
 void cSyslog::Log(const TCHAR* programName, cSyslog::LogType logType, const TCHAR* message)
 {
-#if HAVE_SYSLOG_H && !defined(SKYOS) // Handle an oddball OS that has syslog.h but doesn't implement the calls.
-
+// SkyOS has syslog.h but doesn't actually implement the calls.
+#if SUPPORTS_SYSLOG
+    
     (void)logType; // logType is not used for Unix syslog
 
     ASSERT(sizeof(TCHAR) == sizeof(char));
diff --git a/src/tripwire/tripwirestrings.cpp b/src/tripwire/tripwirestrings.cpp
index 12cffdf..b254d18 100644
--- a/src/tripwire/tripwirestrings.cpp
+++ b/src/tripwire/tripwirestrings.cpp
@@ -34,7 +34,7 @@
 #include "stdtripwire.h"
 #include "tripwirestrings.h"
 
-#ifdef __AROS__
+#if IS_AROS
 # define VERSION_PREFIX "$VER: "
 #else
 # define VERSION_PREFIX "@(#)"
diff --git a/src/tripwire/twcmdline.cpp b/src/tripwire/twcmdline.cpp
index 21f4162..fa02298 100644
--- a/src/tripwire/twcmdline.cpp
+++ b/src/tripwire/twcmdline.cpp
@@ -296,7 +296,7 @@ static void FillOutConfigInfo(cTWModeCommon* pModeInfo, const cConfigFile& cf)
   cf.Lookup(TSTRING(_T("TEMPDIRECTORY")), temp_directory);
 
     if (temp_directory.length() == 0) {
-#ifdef __AROS__
+#if IS_AROS
       temp_directory = "T:";
 #else
       temp_directory = "/tmp/";
@@ -311,7 +311,7 @@ static void FillOutConfigInfo(cTWModeCommon* pModeInfo, const cConfigFile& cf)
     // make sure it exists...
     //
 
-#ifdef __AROS__
+#if IS_AROS
     temp_directory = cArosPath::AsNative(temp_directory);
 #endif
 
diff --git a/src/tw/twinit.cpp b/src/tw/twinit.cpp
index f21f9b1..f3a057e 100644
--- a/src/tw/twinit.cpp
+++ b/src/tw/twinit.cpp
@@ -79,7 +79,7 @@
 #include "core/tw_signal.h"         // to ignore SIGPIPE
 #endif
 
-#ifdef __AROS__
+#if IS_AROS
 #include <errno.h>
 #include <proto/exec.h>
 #include <proto/bsdsocket.h>
@@ -246,7 +246,7 @@ void cTWInit::Init( const TSTRING& strArgv0 )
     // END:RAD
     // ------------------------------------------------------------
 
-#ifdef __AROS__
+#if IS_AROS
     aros_socketbase_init();
 #endif
     //
@@ -284,7 +284,7 @@ void cTWInit::Init( const TSTRING& strArgv0 )
     mpData->et.SetChild( &mpData->er );
     errorQueue.SetChild( &mpData->et );
 
-#if IS_UNIX && !defined(__DJGPP__)
+#if SUPPORTS_POSIX_SIGNALS
     // ignore SIGPIPE
     tw_sigign(SIGPIPE); //TODO: somebody add comment here!
 
@@ -316,7 +316,7 @@ void cTWInit::Init( const TSTRING& strArgv0 )
 
 }
 
-#ifdef __AROS__
+#if IS_AROS
 struct Library* SocketBase=0;
 
 bool aros_socketbase_init()
diff --git a/src/tw/twutil.cpp b/src/tw/twutil.cpp
index a9bb8e7..c6979ba 100644
--- a/src/tw/twutil.cpp
+++ b/src/tw/twutil.cpp
@@ -1141,7 +1141,7 @@ void cTWUtil::GetString(wc16_string& ret)
 #endif
 
 // tcsetattr doesn't seem to work on AROS, so tweak ANSI terminal settings to hide passphrases.
-#ifdef __AROS__
+#if IS_AROS
     printf("\e[8m"); // set the 'concealed' flag
     fflush(stdout);
 #endif
@@ -1154,7 +1154,7 @@ void cTWUtil::GetString(wc16_string& ret)
     TCOUT.flush();
     len = read( 0, buf, MAX_STRING );
 
-#ifdef __AROS__
+#if IS_AROS
     printf("\e[0m"); // reset back to normal text
     fflush(stdout);
 #endif
diff --git a/src/twadmin/twadmincl.cpp b/src/twadmin/twadmincl.cpp
index 0dc5012..19dc79a 100644
--- a/src/twadmin/twadmincl.cpp
+++ b/src/twadmin/twadmincl.cpp
@@ -63,7 +63,7 @@
 #include "core/displayencoder.h"
 
 //Provide a swab() impl. from glibc, for platforms that don't have one
-#if defined(__SYLLABLE__) || defined(__ANDROID_API__) || defined(_SORTIX_SOURCE)
+#if NEEDS_SWAB_IMPL
 void swab (const void *bfrom, void *bto, ssize_t n)
 {
   const char *from = (const char *) bfrom;
diff --git a/src/twadmin/twadminstrings.cpp b/src/twadmin/twadminstrings.cpp
index c23a688..d32e94b 100644
--- a/src/twadmin/twadminstrings.cpp
+++ b/src/twadmin/twadminstrings.cpp
@@ -39,7 +39,7 @@
 #include "twadmin.h"
 #include "twadminstrings.h"
 
-#ifdef __AROS__
+#if IS_AROS
 # define VERSION_PREFIX "$VER: "
 #else
 # define VERSION_PREFIX "@(#)"
diff --git a/src/twparser/policyparser.cpp b/src/twparser/policyparser.cpp
index c9ba3a7..bdedd97 100644
--- a/src/twparser/policyparser.cpp
+++ b/src/twparser/policyparser.cpp
@@ -209,7 +209,7 @@ std::string convert_to_encoded_hex( char ch )
 
 std::string util_ConvertMB( const std::string& sIn )
 {
-#if defined(__ANDROID_API__) || defined(__AROS__)
+#if !USES_MBLEN
   return sIn;
 #else
     cDebug d( "cPolicyParser::util_ConvertMB" );
diff --git a/src/twprint/twprintstrings.cpp b/src/twprint/twprintstrings.cpp
index a49caac..1930851 100644
--- a/src/twprint/twprintstrings.cpp
+++ b/src/twprint/twprintstrings.cpp
@@ -39,7 +39,7 @@
 #include "twprint.h"
 #include "twprintstrings.h"
 
-#ifdef __AROS__
+#if IS_AROS
 # define VERSION_PREFIX "$VER: "
 #else
 # define VERSION_PREFIX "@(#)"