I have been using cross compiled boost static library(system,thread) with ios sdk 4.1 just fine.
(cross compiling part was hell of a job and i don't recall how i 've done that Meh!)
I updated to xcode4 and it fails to link with error msg: Bad codegen, pointer diff in boost::detail....
I saw that some people try to manipulate "Symbols Hidden by Default" and similar option to disable the warning.
I strongly suspect that the error has to be dealt with proper way.(I saw other postings that people had success compiling it with the options changed but they reported frequent crashing)
I wonder anyone has moved to xcode4 with boost successfully.
Please share how you have done if you did.
Thank you