I have now tested my assumptions with gcc:

Nigel@PB-IM2424 ~
$ gcc --version
gcc.exe (GCC) 4.5.0
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There i
+s NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR
+POSE.


Nigel@PB-IM2424 ~
$ gcc -Wall tracking.c
tracking.c: In function 'check_new':
tracking.c:22:5: warning: format '%p' expects type 'void *', but argum
+ent 2 has type 'uintptr_t'
tracking.c:22:5: warning: format '%p' expects type 'void *', but argum
+ent 3 has type 'ptrdiff_t'
tracking.c: At top level:
tracking.c:26:6: warning: return type of 'main' is not 'int'

Nigel@PB-IM2424 ~
$ cat tracking.c
#include <stdio.h>
#define __STDC_LIMIT_MACROS
#include <stdint.h>
#include <stddef.h>

#define ALIGN_BITS  ( sizeof(void*) >> __UINT64_C( 1 ) )
#define BIT_BITS     __UINT64_C( 3 )
#define BYTE_BITS   __UINT64_C( 14 )
#define SLOT_BITS   ( sizeof( void*) * 8 ) - ( ALIGN_BITS + BIT_BITS +
+ BYTE_BITS )
#define BYTES_PER_SLOT  __UINT64_C( 1 ) << BYTE_BITS
#define TRACKING_SLOTS  8192 // max. 8192 for 4GB/32-bit machine

int check_new( uintptr_t p ) {
    ptrdiff_t slot = ( p >> ( ALIGN_BITS + BIT_BITS + BYTE_BITS ) );
    ptrdiff_t byte = ( p >> ( ALIGN_BITS + BIT_BITS)) & ( BYTE_BITS  -
+ 1 );
    ptrdiff_t bit  = ( p >>   ALIGN_BITS)             & ( BIT_BITS   -
+ 1 );
    ptrdiff_t nop  =   p                              & ( ALIGN_BITS -
+ 1 );

    printf(
        "address: %p slot: %p byte: %4x bit: %4x nop:%x\n",
        p, slot, byte, bit, nop
    );
    return 1;
}

void main( void ) {
        uintptr_t p;

        for( p = __UINT64_C( 123456 ); 
             p < ( __UINT64_C( 1 ) << 34 ); 
             p += ( __UINT64_C( 1 ) << 29 ) 
        ) {
                check_new( p );
        }
}
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