How to build universal ios static library

Question

Hi

I'm trying to build a static library that I can use with both ios3.x and ios4.x. I can build a static library with ios3.0 that works with another project in ios3.0 but won't compile in ios4. The same is true going from ios4 to ios3.

Here's how to recreate:

1. Open XCode 3.2.4 and start a new project that's a Cocoa Touch Static Library called Library4
2. Click on the classes folder and create a new UIViewController named "TestViewController"
3. Right click on Frameworks folder, add existing framework, pick UIKit
4. In the left panel, expand targets, right-click on my library target and click get info. Change to all configurations, Change the base sdk to iphone simulator 4.0, change ios deployment target to ios3.0
5. Click on the Link Library with Binaries folder. In the right pane, change the roles of both to "Weak"
6. Build the Library
7. Open Xcode 3.2.2 and start a new View based application called Library4Test
8. Copy TestViewController.h to the classes folder
9. Copy libLibrary4.a file to the frameworks folder. It automatically gets added to the linker phase of the target
10. Right-click on the Library4Test Target and click get info. In other linker flags, add "-ObjC" and "-all_load"
11. In the app delegate header add Import "TestViewController.h"

12. IN the app delegate header's application's didFinishLaunchingWithOptions method add

    TestViewController *test = [TestViewController alloc] init;

13. Compile with ios3.0 simulator

When I compile I get:

Ld build/Debug-iphonesimulator/library4Test.app/library4Test normal i386
cd /Users/test/Documents/Testing/library4Test
setenv MACOSX_DEPLOYMENT_TARGET 10.5
setenv PATH "/Developer/GrandpaIPhone/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/GrandpaIPhone/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Developer/GrandpaIPhone/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 -arch i386 -isysroot /Developer/GrandpaIPhone/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator3.1.3.sdk -L/Users/test/Documents/Testing/library4Test/build/Debug-iphonesimulator -L/Users/test/Documents/Testing/library4Test -F/Users/test/Documents/Testing/library4Test/build/Debug-iphonesimulator -filelist /Users/test/Documents/Testing/library4Test/build/library4Test.build/Debug-iphonesimulator/library4Test.build/Objects-normal/i386/library4Test.LinkFileList -mmacosx-version-min=10.5 -framework Foundation -framework UIKit -framework CoreGraphics -llibrary4_1 -o /Users/test/Documents/Testing/library4Test/build/Debug-iphonesimulator/library4Test.app/library4Test

Undefined symbols:
"_objc_msgSendSuper2", referenced from:
-TestViewController didReceiveMemoryWarning in liblibrary4_1.a(TestViewController.o)
-TestViewController viewDidUnload in liblibrary4_1.a(TestViewController.o)
-TestViewController dealloc in liblibrary4_1.a(TestViewController.o)
"__objc_empty_vtable", referenced from:
_OBJC_METACLASS_$_TestViewController in liblibrary4_1.a(TestViewController.o)
_OBJC_CLASS_$_TestViewController in liblibrary4_1.a(TestViewController.o)
"_OBJC_CLASS_$_UIViewController", referenced from:
_OBJC_CLASS_$_TestViewController in liblibrary4_1.a(TestViewController.o)
"_OBJC_METACLASS_$_UIViewController", referenced from:
_OBJC_METACLASS_$_TestViewController in liblibrary4_1.a(TestViewController.o)
".objc_class_name_TestViewController", referenced from:
literal-pointer@__OBJC@__cls_refs@TestViewController in library4_1os3TestAppDelegate.o
"_OBJC_METACLASS_$_NSObject", referenced from:
_OBJC_METACLASS_$_TestViewController in liblibrary4_1.a(TestViewController.o)
ld: symbol(s) not found
collect2: ld returned 1 exit status