I came across a situation where I had to replace an object file in a static library. First problem encountered was that it was a “fat” library – it had the same code compiled for multiple architectures. The architectures included can be displayed with this command:
lipo -archs fred.a
To get around this, it was necessary to create a new thin library with just the architecture in which I was interested – arm64 in this case. This can be done with lipo again:
lipo fred.a -thin arm64 -output fred64.a
fred64.a will just contain the version for the chosen architecture. In my case, I wanted to replace a large set of object files so I decided to just expand the static library into all of its component object files:
ar x fred64.a
Then I could easily replace the necessary object files. Finally, I recreated the thin library:
ar cr fred64new.a *.o
It’s easy to check what is in the new library using:
ar t fred64new.a
For even more detail, the nm command will display the exposed symbols in the library:
nm fred64new.a
Meca Sciences 