Suppose I have .so file under Linux (i.e. a DLL) and I want to convert it into .a (static library) - is it possible ?

I've tried WEB search, and it shows how to do the opposite, i.e. how to convert .a -> .so , which is pretty trivial (ar -x ..., relink).

I mean "binary" conversion, i.e. not rebuilding/relinking from source, i.e. let's assume there is access only to .so file and not to sources.

Alternatively, directly obtaining a statically linked executable with .so would do, but not relying on .so at runtime.

The ar command doesn't do anything to the internal content of any files it's putting into or taking out of an archive. So use ar with confidence to create libraries, make single copies of files that existed in libraries, and rename those single copies to your heart's content.

Have you ever tried 'ar' on .so files ?

Good point. Although my original statement is correct, I'm afraid it isn't very helpful; sorry about that.

I've done some googling about your question (and I'm sure you did, too). I don't find anything very helpful.

If I were in your position and I had copious amounts of free time, I would look into the source for the linker, and see whether the building of a shared library removes information which would be necessary to work backwards to the original .a files from a .so file. If no such information is removed, I would write a quick and dirty utility to go in the direction you desire. If it is removed, you're out of luck.

In other words, I can't help you. Sorry. :(

I've never heard about a possibility to do so. I also can't imagine it working since shared objects are some form of executable files, while static libs are collections of objects/functions, so the question would be if they are even able to have the necessary informations to recreate the object files.
Another things that question the plausibility to me is when you think about shared objects that for themselves have dependencies on other shared objects and those too, etc. ... would such a roundtrip make sense ?

I'm genuinely curious too though, so if anyone can give a definitive 'Yes' or 'No', please do so.

The item in bold is not quite correct WRT the thread.

For example,

happily works on my machine.

And remember, linker ('ld') easily gets satisfaction (== resolves symbols) both in case of .a and .so file, though in the latter case final binding occurs during runtime.

Also, .so files are bigger than the same .a file.

So, I think, .so files contains all the info needed to create a .a file plus more.

...

Maybe 'objcopy' can do the job in a number of passes - haven't tried 'objcopy' at all yet.

Well isn't that more like a special case ? I was talking about straight dynamic libraries (ELF for example), which don't necessarily need to contain all symbol informations.

Of course, if a file does not contain all symbol information, it can't be used for linking, but this is not what this thread is about.

If a shared object doesn't have all symbols as info doesn't mean it's not linkable, so that's not correct to say I'm afraid. It would be kinda useless if it wasn't linkable, wouldn't it ?

Has anyone figured out how to convert a .so (shared library) to a .a (static library)?

Try the 'objdump -d' idea, i.e. to disassemble and then to recompile into .o files, then to create static library.

I haven't tried it myself, but seems like a good start.