OS X: convert .dylib to .a/.o (dynamic to static)?

Question

Suppose I've read this caveat, and I still want to use TBB as a statically-linked library. (Pretend I'm working in an environment where users aren't allowed to create their own dylibs.) But I don't really want to rewrite the TBB makefile to generate libtbb.a instead of libtbb.dylib.

Is there a simple command-line way to convert libtbb.dylib into libtbb.o with the same entry points?

I have heard a good argument for not being able to go the other way, from static to dynamic. Namely: dynamic libraries need to be PIC, and converting a non-PIC static library to PIC isn't feasible. But that argument doesn't apply in the other direction, as far as I know.

Here's someone saying it's impossible to convert .dll to .a on Windows, but I think they're just talking about the impossibility of breaking a .dll or .exe back up into its original .o files, not necessarily saying it would be impossible to create a linkable .o file with the same contents. Also, the situation on Windows is slightly odder than "real" PIC, although I don't think that's relevant.

Answer 1

Intel Threading Building Blocks (TBB) is available as binary for Windows, Mac and Linux. If you expect to use libtbb.dylib from the Mac distribution on iOS then you are out of luck. The Mac distribution is targeted for Intel (32 and 64 bits). Since iOS runs on ARM processors, you could not use it, even if you found a way to convert a dynamic library to a static library.

If you found a libtbb.dylib file somewhere else targeted for ARM, then you could probably use it on iOS. It's actually possible to load dynamic libraries on iOS. Have a look at the dlopen(3) man page.

Finally, you should read about Grand Central Dispatch (GCD) instead, which is built-in support for concurrent code execution on multicore hardware in iOS and OS X.