Xcode 4.2 link error: libz issue?

Question

Moving a project to Xcode 4.2, I am getting a number of Mach-O linker unresolved errors, for things like _crc32, _expf, and _UnwindSjLj_Register, on a project that compiles

Answer 1

Link against the libz.dylib, but add it through the Build Phases tab.

Project >> Target >> Build Phases >> Link Binary With Libraries

Press + under the list and select the libz.dylib then it will add the lib so it will work inbetween SDK updates.