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.
The version of Visual C++ in Visual Studio 2015 Update 2 includes a new flag to link.exe
called /WHOLEARCHIVE
, which has equivalent functionality to the --whole-archive
option to ld
. According to the flag documentation:
The
/WHOLEARCHIVE
option forces the linker to include every object file from either a specified static library, or if no library is specified, from all static libraries specified to the LINK command.
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answer is now almost 7 years old and the statements regarding the availability of options in the MSVC++ toolchain are outdated.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.
I believe about the closest equivalent would be /OPT:NOREF
.
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