C++ Executing functions when a static library is loaded

Question

I need to register classes when the code is loading. I implemented a solution which works great as long as the code is compiled in the app.

But when the code is provided by a static library it doesn't work at all.

I solved this problem in a fashion similar to this answer: https://stackoverflow.com/a/729028/171711.

Currently I have something like:

#define REGISTER(className)\
static const int __classDescriptor##className = MyRegister(#className, className::GetAllocator());

When used it looks like:

//Foo.cpp

REGISTER(Foo);

Foo::Foo()
{
  ...
}

And I have in the logs:

registered class:Foo

But when I created a static library and Foo is provided by the library the problem is that REGISTER(Foo); is never called.

I have a complex loading system to allow scripts to use native C++ classes which is dependent on this behavior. Is there a way to force the code in Foo.cpp to execute when the library is loaded?

Edit: It seems my question is directly related to the one about static linking in Visual Studio. It seems I have the same problem with my own libraries. I noticed that some of the classes from the library are registered. And they are only the ones which have their .h file included in my project.

So is there a way to execute code in a lib without linking to the .h file?

`REGISTER(Foo)` is never meant to be called, it's a macro.... — Luchian Grigore, Sep 26 '12 at 13:11
@LuchianGrigore: static const int __classDescriptor... is called through REGISTER(Foo). That's what I need and that's what the question tries to focus on. — Coyote, Sep 26 '12 at 13:13

score 4 · Accepted Answer · answered Sep 07 '13 at 21:50

4

Use the -all_load linker option to load all members of static libraries. Or for a specific library, use -force_load path_to_archive.

In Xcode, you'll want to add these options under "Other Linker Flags" for your executable (not your static library).

This fixed the problem for my static initialization functions.

answered Sep 07 '13 at 21:50

Taylor

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I'll have to make a new project to test this. – Coyote Sep 09 '13 at 09:55

score 1 · Answer 2 · answered Dec 31 '12 at 02:11

The only way to initialize my classes descriptors before any other code relying on them is called is to initialize the library.

I added a function MyLibraryInit() which calls a function on each __classDescriptor##className to force the initialization of each descriptor.

Unfortunately it seems to be the most elegant approach I could find.

C++ Executing functions when a static library is loaded

2 Answers2