Use the /Gw option when compiling real-mode Windows modules containing far functions marked as __export. The /Gw option instructs the compiler to generate entry/exit code sequences for real-mode Windows call-back functions.
Use the /GW option when compiling real-mode Windows modules containing only functions not marked as __export. The /GW option is similar to the /Gw option, but generates a more efficient entry sequence for real-mode windows functions that are not callback functions.
See the Microsoft Windows Software Development Kit for more information. Both options define the _WINDOWS constant, declared in the Windows version of STDIO.H.
Note:
The /GW option has been improved for Microsoft C/C++. Use the /Gq option, described earlier in this chapter, if you need the entry/exit code generated by previous versions of /GW.
The /GA, /GD, and /GE options, described earlier in this chapter, perform entry/exit code that will run only under standard- or enhanced-mode Windows. Use of these options can save up to 10 bytes and 7 instructions for each function call.