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Avoid duplicate symbol in static library and its customer

发布static library给使用者使用。在实际的工程实践中，iOS静态库一般会在对外/对内提供SDK时出现。

静态库(SDK)本身可能依赖一些第三方的库，当使用该SDK的App也依赖了同样的第三方库，那么问题就来啦。

Figure: SDK 和 SDK Customer 依赖相同的3rd library

1. static library如何避免和使用者的代码有重复符号 

Ref[1] Ref[4]

2. 从iOS的静态库中抽取出object file

Ref[5]

1 $ lipo libXXXSDK.a -thin armv7 -output libXXXSDK-armv7.a
2 $ ar -x libXXXSDK-armv7.a

3. 发布静态库

3.1 发布支持模拟器和真机的静态库

Ref[6] Ref[7]

3.2 debug编译和release编译的静态库区别

A: NSLog

debug: NSLog会输出 

release: NSLog不会输出

3.3 如何strip静态库的符号表

A) 隐藏静态库的符号

Ref[17]

" Hiding internal names requires a few simple Xcode build settings, and it is not generally

necessary to modify source or change the type of the built product.

1. Eliminate any internal symbols required between modules by performing a single-object prelink.

Set the Xcode build setting named "Perform Single-Object Prelink" to Yes (GENERATE_MASTER_OBJECT_FILE=YES).

This causes ld to be run with the "-r" flag.

2. Make sure that the setting "Strip Style" is set to "Non-global symbols" (STRIP_STYLE=non-global), this passes "-x" to ld.

Stripping is only actually performed on static libraries if post-processing is enabled (and this is not the default).

3. Set Xcode build setting "Deployment Postprocessing" to yes. (DEPLOYMENT_POSTPROCESSING=YES).

Also make sure that "Use separate strip" is set to Yes (not always the default).

4. If, in addition to local symbols, if you need to remove some of the global symbols you can supply additional

options to the strip command, under the Xcode build setting "Additional strip flags". E.g. I commonly

use the strip "-R somefile" option to provide a file with an additional list of symbols which I want removed

from the global symbol table." Ref[17]

关于"STRIP_SYTLE" 参考Ref[19]

B) 将静态库的符号表剔除后, 会出现这种情况: 静态库出现crash时，无法将地址符号化。Ref[18]

C) 那么静态库的符号被strip掉后, 会不会像App被生成.dSYM文件呢? 或者其他类似的东西?

3.4 自动构建多architecture的静态库

Ref[15] 

3.5 当发布商业的静态库时，选择debug configuration 还是release configuration呢?

Ref[16]

Reference

1. Avoiding dependency collisions in iOS static library managed by CocoaPods  (AAAA+)

http://blog.sigmapoint.pl/avoiding-dependency-collisions-in-ios-static-library-managed-by-cocoapods/

2. Using Static Libraries in iOS

https://developer.apple.com/library/ios/technotes/iOSStaticLibraries/Articles/creating.html

3. UNIX ar Examples: How To Create, View, Extract, Modify C Archive Files (*.a)

http://www.thegeekstuff.com/2010/08/ar-command-examples/

4. Avoiding duplicate symbol errors during linking by removing classes from static libraries  (ToRead)

http://atnan.com/blog/2012/01/12/avoiding-duplicate-symbol-errors-during-linking-by-removing-classes-from-static-libraries

5. Extract object (*.o) files from an iPhone static library

6. How to build a library for both iPhone simulator and device? 

7. Build fat static library (device + simulator) using Xcode and SDK 4+

8. Distributing your Static Library

http://www.akitaonrails.com/2011/04/24/objective-c-distributing-your-static-library#.VZY4ShOqqko

9. Xcode 6 drops armv7s

https://www.cocoanetics.com/2014/10/xcode-6-drops-armv7s/

10. iOS Static Libraries Are, Like, Really Bad, And Stuff  (ToRead)

http://landonf.org/code/ios/Radar_15800975_iOS_Frameworks.20140112.html

11. Strip debug symbol from universal static libraries (tested for iOS only)

https://gist.github.com/neonichu/1662881

12. An XCode project template to build universal frameworks (arm7, arm7s, and simulator) for iOS / iPhone.

https://github.com/kstenerud/iOS-Universal-Framework

13. http://www.raywenderlich.com/41377/creating-a-static-library-in-ios-tutorial (AAAA+)

14. strip nmeidt symbols: 编辑符号的工具

https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/symbols.1.html 

15. Automatic build of static library for iOS and many architectures (AAAA+)

http://blog.sigmapoint.pl/automatic-build-of-static-library-for-ios-for-many-architectures/

16. How to distribute Static libraries?

http://stackoverflow.com/questions/5730432/how-to-distribute-static-libraries/5778007#5778007

"So, long story short : just distribute a fat, release version of your library !" 

17. strip symbol in static library

17.1 Symbol hiding in static libraries built with Xcode/gcc

17.2 Symbolification: Shipping Symbols

http://bdunagan.com/2010/05/15/symbolification-shipping-symbols/

17.3 How to solve symbolication problems --> "Build settings for getting proper symbol data"

http://support.hockeyapp.net/kb/client-integration-ios-mac-os-x/how-to-solve-symbolication-problems

17.4 xcode build settings for debug symbol

http://jonathanblog2000.blogspot.tw/2013/07/xcode-build-settings-for-debug-symbol.html

18. Symbolicating crash log for app with static library

19. Xcode Build Setting Reference

https://developer.apple.com/library/ios/documentation/DeveloperTools/Reference/XcodeBuildSettingRef/1-Build_Setting_Reference/build_setting_ref.html

https://developer.apple.com/library/mac/technotes/tn2004/tn2123.html#SECNOSYMBOLS

iOS.StaticLibrary.1-avoid-duplicate-symbol-in-static-library[draft]

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原文地址：http://www.cnblogs.com/cwgk/p/4618637.html