Problem with malloc (WinARM, GCC 4.0.2)

I can't build the program with memory allocation functions thats work
correctly.

I definded _sbrk() and _sbrk_functions, but malloc returns zero-pointer,
or getting stick in after second call of _sbrk_r().

CPU - LPC2214
i tried to compile syscalls.c in pure arm mode and in thumb-interwork,
but result is same

----------------syscalls.c cut------------------------------------

 extern char _end;

 caddr_t _sbrk(int incr)
{
     HalDebugInfo("sbrk\n");
     static unsigned char *heap_end =0;
     unsigned char *prev_heap_end=0;

     if( heap_end == 0 ) heap_end = (caddr_t)&_end;

     prev_heap_end = heap_end;
     heap_end += incr;
     return(caddr_t) prev_heap_end;
 }

void *_sbrk_r(struct _reent* reent, ptrdiff_t incr)
{
  return _sbrk(incr);
}
-----------------------------------------------------------------
Whats version of libc should i use ?

..\arm-elf\lib\interwork\libc.a           // the program get stack in
after
                                          // second _sbrk_r call

..\arm-elf\lib\thumb\interwork\libc.a     // malloc always return zero
pointer


..\arm-elf\lib\be\interwork
..\arm-elf\lib\be\nofmult


Does anybody has a working code for memory functions ?