Question

When linking a static library against an executable, unreferenced symbols are normally discarded. In my case some otherwise unused objects are used to register their respective classes into a factory and if the objects are discarded, this registration fails.

Under Unix where we use gcc, I can pass the flag –whole-archive to the linker ld (see excerpt from ld documentation below), which makes ld not discard any objects. Is there anything like this for Visual C++?

–whole-archive

    For each archive mentioned on the command line after the
    `–whole-archive’ option, include every object file in the archive
    in the link, rather than searching the archive for the required
    object files. This is normally used to turn an archive file into
    a shared library, forcing every object to be included in the
    resulting shared library. This option may be used more than once.

Answer 1

To my knowledge, there is no single option which reliably guarantees that. There are combinations of optimizing options which (silently) deactivate this, so no way… /INCLUDE works, but for that you need to extract and hardcode the mangled name of the symbol. You have two choices: (1) ensure, that all registrars are contained (included) in the translation unit containing main and enforce their usage. (2) Give up this ‘idiom’ and use explicit registration.

Caution: this answer is now almost 7 years old and the statements regarding the availability of options in the MSVC++ toolchain are outdated. Nevertheless I still recommend not to rely on registrar pattern and look at the alternatives.