Question

I am working on a cross platform project in C++, under IOS and Android, and I am having the following situation
:

I am writing a library used to load scene graphs directly from xml files describing them. The library has a base tree node class, that implements all the functionality to make a class constructable by it’s name. Then additional tree nodes are implemented, all deriving from this base node class. This works excellent but there is one problem. The linker ‘thinks’ that some of my classes are not going to be used and strips them out of the library. I have a nasty workaround right now, having a file that includes all existing nodes headers, and in this file one instance of every node is being created and altered to indicate the compiler/linker that this class is really being used.

Does anybody know a good design pattern that can be used to automatically generate the required instances of all classes?

I have tried to create macros that are placed into the classes cpp file that creates a static instance of the given class, but the linker still detects that those static instances are never going to be referenced.

Or is there a linker flag that can be used to tell the linker not to strip any unused classes out? Like already mentioned: I am working on Android (ndk 6.0) and on IOS (xcode 4.2)

This problem is not going to be a showstopper for my project but it would really be nice to find an acceptable solution here.

Answer 1

It is implementation-defined whether the dynamic initialization of a non-local variable with static storage
duration is done before the first statement of main. If the initialization is deferred to some point in time
after the first statement of main, it shall occur before the first odr-use (3.2) of any function or variable
defined in the same translation unit as the variable to be initialized.

Therefore there’s no standard way to guarantee the construction of those objects but to list them all in one specific place.