OSX: How do I convert a static library to a dynamic one?

Question

Suppose I have a third party library called somelib.a on a Mac running Mountain Lion with Xcode 4.4 installed. I want to get a dynamic library out of it called somelib.dylib. An

Answer 1

Note: A link for the documentation of the OSX ld linker.

http://www.unix.com/man-page/osx/1/ld/

I know it is late to give an answer for this, but I do not have enough reputation to make a comment on @hanslovsky answer. However, it helps me a lot to have the docs of the options too. It helps what the options do exactly, and that other options the ld linker also has. So I just wanted to share with others who finds linking an issue.

UPDATE:

After the comment from @GhostCat I have decided to expand my answer.

The docs for -all_load is:

-all_load

Loads all members of static archive libraries.

So it loads for all static libraries that you note. If you want something similar to --whole-archive and --no-whole-archive, then you need to use -force_load and -noall_load.

-force_load "path_to_archive"

Loads all members of the specified static archive library. Note: - all_load forces all members of all archives to be loaded.
This option allows you to target a specific archive.

-noall_load

This is the default. This option is obsolete.

Then you can define which libraries to fully load with -force_load and then later turn it off again with -noall_load.

Answer 2

According to the ld manual, -noall_load is the default and is ignored. (If you use it, you get an error message: ld: warning: option -noall_load is obsolete and being ignored)

Apparently the way to get -all_load to apply to only one library is as follows:

-Wl,-force_load,somelib.a

Answer 3

I found out the solution to my problem:

g++ -fpic -shared -Wl,-all_load somelib.a -Wl,-noall_load -o somelib.dylib

The required arguments are -all_load and -noall_load.