/Gy
This option allows the compiler to package individual functions in the form of packaged functions (COMDATs). The linker requires that functions be packaged separately as COMDATs to exclude or order individual functions in a DLL or .exe file.
You can use the linker option /OPT:REF to exclude unreferenced packaged functions from the .exe file.
You can use the linker option /ORDER to place packaged functions in a specified order within the .exe file.
Inline functions are always packaged if they are instantiated as calls (which occurs, for example, if inlining is turned off or you take a function address). In addition, C++ member functions defined within the class declaration are automatically packaged; other functions are not, and selecting this option is required to compile them as packaged functions.
Note The /ZI option, used for Edit and Continue, automatically sets the /Gy option.
Compiler Options | Setting Compiler Options