The /PACKFUNCTIONS option is on by default. This option removes unreferenced functions from the executable file if they were compiled with /Gy (enable function-level linking). This reduces the size of your program significantly.
If you want to keep unreferenced functions in your executable (for example, for debugging purposes), you can turn off the /PACKFUNCTIONS option by specifying /NOPACKFUNCTIONS. See Chapter 14, “Linking Object Files with LINK,” of the Environment and Tools manual for more information.