krhplatform.h currently contains:

/*
 * Types that are (so far) the same on all platforms
 */
typedef signed   char          khronos_int8_t;
typedef unsigned char          khronos_uint8_t;
typedef signed   short int     khronos_int16_t;
typedef unsigned short int     khronos_uint16_t;
typedef signed   long  int     khronos_intptr_t;
typedef unsigned long  int     khronos_uintptr_t;
typedef signed   long  int     khronos_ssize_t;
typedef unsigned long  int     khronos_usize_t;

However, 64bit Windows uses an LLP64 model¹, where longs are 32bits and pointers are 64bits.

Thus the definitions khronos_{u,}intptr_t and khronos_{s,u}size_t need to be specialised.

For the C99 case this could just be to typedef the existing {u,}intptr_t, and for POSIX at least to typedef ssize_t to khronos_ssize_t and size_t to khronos_usize_t.

1: http://technet.microsoft.com/en-us/library/bb496995.aspx