/POINTER_SIZE

    /POINTER_SIZE=option
    /NOPOINTER_SIZE (D)

 Controls whether or not pointer-size features are enabled, and
 whether pointers are 32 bits or 64 bits long.

 The default is /NOPOINTER_SIZE, which disables pointer-size
 features, such as the ability to use #pragma pointer_size, and
 directs the compiler to assume that all pointers are 32-bit
 pointers.  This default represents no change over previous versions
 of the compiler.

 You must specify one of the following options:

   SHORT       The compiler assumes 32-bit pointers.

   32          Same as SHORT.

   LONG[=ARGV] The compiler assumes 64-bit pointers. If the ARGV option to 
               LONG or 64 is present, the main argument argv will be an 
               array of long pointers instead of an array of short pointers.

   64[=ARGV]   Same as LONG.

 Specifying /POINTER_SIZE=32 directs the compiler to assume that all
 pointers are 32-bit pointers.  But unlike the default of
 /NOPOINTER_SIZE, /POINTER_SIZE=32 enables use of the #pragma
 pointer_size long and #pragma pointer_size short preprocessor
 directives to control pointer size throughout your program.

 Specifying /POINTER_SIZE=64 directs the compiler to assume that all
 pointers are 64-bit pointers, and also enables use of the #pragma
 pointer_size directives.