Far Pointer Comparisons Assume Same Segment

MS-DOS                 | OS/2       | WINDOWS

The information in this article applies to:

• The Microsoft C/C++ Compiler (CL.EXE), included with:

      - Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
      - Microsoft C for OS/2, versions 6.0 and 6.0a
      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
  

When code created with one of the compilers listed above uses the < (less than), > (greater than), <= (less than or equal to), or >= (greater than or equal to) operators to compare pointers, the pointers must be in the same segment. The == (equality) operator tests both segment and offset to prevent two pointers that have the same offset value, but different segment values, from comparing as equal.

The <, >, <=, and >= operators assume that the compared pointers share the same segment because, according to the ANSI standard, an application can compare pointers for precedence only if they point to the same object. In a segment architecture such as that of an Intel microprocessor, two pointers to the same object must share the same segment value unless the pointers are declared to point to a huge object. The compiler performs 32-bit arithmetic to compare huge pointers.