diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 481bef6f7b..4fdf61e9e6 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -17,6 +17,22 @@
    past entries belonging to author(s): Viktor Szakats.
 */
 
+2009-11-22 12:38 UTC+0100 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
+  + harbour/config/linux/clang.mk
+    + added support for CLANG in LINUX builds
+
+  * harbour/include/hbatomic.h
+    + added assembler code for SPINLOCKs in WATCOM x86 builds
+
+  * harbour/src/vm/fm.c
+    * enabled HB_FM_DLMT_ALLOC by default in MT HVM if HB_FM_DL_ALLOC is
+      also enabled
+
+  * harbour/src/vm/dlmalloc.c
+    * modifications for non MS-Windows WATCOM builds
+      TOFIX: now it compiles in Linux and OS2 builds but it still does not
+             work
+
 
 2009-11-22 12:29 UTC+0100 Viktor Szakats (harbour.01 syenar.hu)
   * contrib/hbwin/win_prn2.c
diff --git a/harbour/config/linux/clang.mk b/harbour/config/linux/clang.mk
new file mode 100644
index 0000000000..387e9da3d3
--- /dev/null
+++ b/harbour/config/linux/clang.mk
@@ -0,0 +1,69 @@
+#
+# $Id: clang.mk 12957 2009-11-21 10:11:32Z vszakats $
+#
+
+ifeq ($(HB_BUILD_MODE),cpp)
+   # -ccc-clang-cxx
+   HB_CMP := clang
+else
+   HB_CMP := clang
+endif
+
+OBJ_EXT := .o
+LIB_PREF := lib
+LIB_EXT := .a
+
+HB_DYN_COPT := -DHB_DYNLIB -fpic
+
+CC := $(HB_CCACHE) $(HB_CCPREFIX)$(HB_CMP)$(HB_CCPOSTFIX)
+ifneq ($(filter --analyze, $(HB_USER_CFLAGS)),)
+   CC_IN :=
+else
+   CC_IN := -c
+endif
+CC_OUT := -o
+
+CPPFLAGS := -I. -I$(HB_INC_COMPILE)
+CFLAGS :=
+LDFLAGS :=
+
+ifneq ($(HB_BUILD_WARN),no)
+   CFLAGS += -Wall -W
+endif
+
+ifneq ($(HB_BUILD_OPTIM),no)
+   CFLAGS += -O3
+endif
+
+ifeq ($(HB_BUILD_DEBUG),yes)
+   CFLAGS += -g
+endif
+
+ifneq ($(filter $(HB_BUILD_STRIP),all lib),)
+   ARSTRIP = && strip -S $(LIB_DIR)/$@
+endif
+ifneq ($(filter $(HB_BUILD_STRIP),all bin),)
+   LDSTRIP := -s
+   DYSTRIP := -s
+endif
+
+LD := $(HB_CCACHE) $(HB_CCPREFIX)$(HB_CMP)$(HB_CCPOSTFIX)
+LD_OUT := -o
+
+LIBPATHS := $(foreach dir,$(LIB_DIR) $(SYSLIBPATHS),-L$(dir))
+LDLIBS := $(foreach lib,$(HB_USER_LIBS) $(LIBS) $(SYSLIBS),-l$(lib))
+
+LDFLAGS += $(LIBPATHS)
+
+AR := $(HB_CCPREFIX)ar
+ARFLAGS :=
+AR_RULE = ( $(AR) $(ARFLAGS) $(HB_USER_AFLAGS) rcs $(LIB_DIR)/$@ $(^F) $(ARSTRIP) ) || ( $(RM) $(LIB_DIR)/$@ && false )
+
+DY := $(CC)
+DFLAGS := -shared $(LIBPATHS)
+DY_OUT := -o$(subst x,x, )
+DLIBS := $(foreach lib,$(HB_USER_LIBS) $(SYSLIBS),-l$(lib))
+
+DY_RULE = $(DY) $(DFLAGS) $(HB_USER_DFLAGS) $(DY_OUT)$(DYN_DIR)/$@ $^ $(DLIBS) $(DYSTRIP) && $(LN) $(@F) $(DYN_FILE2)
+
+include $(TOP)$(ROOT)config/rules.mk
diff --git a/harbour/include/hbatomic.h b/harbour/include/hbatomic.h
index 4a05b67c9e..f1e80e57c5 100644
--- a/harbour/include/hbatomic.h
+++ b/harbour/include/hbatomic.h
@@ -337,6 +337,55 @@ HB_EXTERN_BEGIN
 
 #     endif
 
+      static inline int hb_spinlock_trylock( volatile int * p )
+      {
+         int i = 1;
+         _asm {
+            mov eax, i
+            mov edx, p
+            xchg eax, dword ptr [edx]
+            mov i, eax
+         }
+         return i;
+      }
+
+      static inline void hb_spinlock_acquire( volatile int * l )
+      {
+         for( ;; )
+         {
+            if( !hb_spinlock_trylock( l ) )
+               return;
+
+            #ifdef HB_SPINLOCK_SLEEP
+               if( !hb_spinlock_trylock( l ) )
+                  return;
+               #if defined( HB_TASK_THREAD )
+                  hb_taskYield();
+               #elif defined( HB_OS_WIN )
+                  Sleep( 0 );
+               #elif defined( HB_OS_OS2 )
+                  DosSleep( 0 );
+               #elif defined( __SVR4 )
+                  thr_yield();
+               #elif defined( HB_OS_UNIX )
+                  sched_yield();
+               #else
+                  sleep( 0 );
+               #endif
+            #endif
+         }
+      }
+
+      static inline void hb_spinlock_release( volatile int * l )
+      {
+         *l = 0;
+      }
+
+#     define HB_SPINLOCK_T          volatile int
+#     define HB_SPINLOCK_INIT       0
+#     define HB_SPINLOCK_ACQUIRE(l) hb_spinlock_acquire(l)
+#     define HB_SPINLOCK_RELEASE(l) hb_spinlock_release(l)
+
 #  endif    /* x86 */
 
 #endif  /* ??? C compiler ??? */
diff --git a/harbour/src/vm/dlmalloc.c b/harbour/src/vm/dlmalloc.c
index 37974f2222..c77ec11f07 100644
--- a/harbour/src/vm/dlmalloc.c
+++ b/harbour/src/vm/dlmalloc.c
@@ -467,11 +467,13 @@ DEFAULT_MMAP_THRESHOLD       default: 256K
 #endif  /* HAVE_MORECORE */
 #endif  /* DARWIN */
 
-#if defined(HB_OS_OS2) && defined(__WATCOMC__)
-#ifndef HAVE_MMAP
+#if defined(__WATCOMC__) && !defined(WIN32)
 #define HAVE_MMAP 0
-#endif
+#define HAVE_MORECORE 0
+#if !defined(HB_OS_OS2)
+#define LACKS_SYS_PARAM_H
 #endif  /* OS2 */
+#endif  /* __WATCOMC__ */
 
 #ifndef LACKS_SYS_TYPES_H
 #include <sys/types.h>  /* For size_t */
@@ -1395,7 +1397,7 @@ static int win32munmap(void* ptr, size_t size) {
     unique mparams values are initialized only once.
 */
 
-#if defined( HB_OS_OS2 ) || defined( HB_OS_WIN )
+#if defined( HB_OS_OS2 ) || defined( HB_OS_WIN ) || defined( __WATCOMC__ )
 #  ifndef HB_SPINLOCK_USE
 #     define HB_SPINLOCK_USE
 #  endif
diff --git a/harbour/src/vm/fm.c b/harbour/src/vm/fm.c
index 51a83f90e8..f4674793f2 100644
--- a/harbour/src/vm/fm.c
+++ b/harbour/src/vm/fm.c
@@ -114,6 +114,7 @@
 
 #if defined( HB_FM_STD_ALLOC )
 #  undef HB_FM_DL_ALLOC
+#  undef HB_FM_DLMT_ALLOC
 #  undef HB_FM_WIN_ALLOC
 #elif !defined( HB_FM_DL_ALLOC ) && !defined( HB_FM_WIN_ALLOC )
 #  if defined( _MSC_VER ) || defined( __BORLANDC__ ) || defined( __MINGW32__ ) || \
@@ -135,6 +136,10 @@
 /* #define HB_PARANOID_MEM_CHECK */
 
 #if defined( HB_FM_DL_ALLOC )
+#  if !defined( HB_FM_DLMT_ALLOC ) && !defined( HB_FM_DLMT_ALLOC_OFF ) && \
+      defined( HB_MT_VM )
+#     define HB_FM_DLMT_ALLOC
+#  endif
 /* #  define NO_MALLINFO 1 */
 /* #  define INSECURE */
 /* #  define USE_DL_PREFIX */