write() Will Not Work Correctly with SS != DS

MS-DOS                      | OS/2            | WINDOWS

The information in this article applies to:

• The C Run-time (CRT), included with:

      - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
      - Microsoft C for OS/2, versions 5.1, 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
  

In code compiled with one of the products listed above, the write() function does not work correctly in text mode in any memory model when SS != DS; the function works correctly in binary mode. In text mode, write() builds a buffer on the stack to do LF to CR/LF translation. It makes a call to the functions stackavail() to make sure it does not overflow the stack; this call is what prevents it from working with SS != DS.

In Microsoft C 5.1, only the functions in the OS/2 multithreaded run- time library and the OS/2 DLL run-time library are designed to support SS != DS. In Microsoft C 6.0, all compact and large memory model run- times support SS != DS in addition to the OS/2 multithreaded run-time and the OS/2 DLL run-time. And, in Microsoft C/C++ 7.0 and Visual C++ for Windows, all compact and large memory model run-times support SS != DS, in addition to the Windows DLL run-time.