Bitcode-enabled static library not backwards-compatible with Xcode 6 and older
| Originator: | joachimb | ||
| Number: | rdar://21884601 | Date Originated: | 17-Jul-2015 05:33 PM |
| Status: | Open | Resolved: | |
| Product: | Developer Tools | Product Version: | Xcode 7 beta 3 |
| Classification: | Other Bug | Reproducible: | Always |
Summary:
I build a proprietary SDK for a living at Lookback, where we ship a static archive .framework. We have so far been able to ship a single distribution for all OSes and Xcodes, and would love to continue doing so. However, enabling Bitcode and doing Build & Archive in Xcode 7 generates a static library which has duplicate symbols when linked with an app in Xcode 6.
Steps to Reproduce:
1. Create a “Static Library” project in Xcode 7
2. Enable Bitcode on it
3. Build and Archive
4. Create an “iOS App” project in Xcode 6
5. Link the previous static library into this app
Expected Results:
6. Works fine
Actual Results:
7. Duplicate symbols
duplicate symbol _llvm.cmdline in:
../HD/Lookback.framework/Lookback(Lookback.o)
../HD/Lookback.framework/Lookback(GFUIKitFunctions.o)
duplicate symbol _llvm.embedded.module in:
../HD/Lookback.framework/Lookback(Lookback.o)
../HD/Lookback.framework/Lookback(GFUIKitFunctions.o)
… and so on for quite a while
Regression:
Haven’t had a compatibility issue like this since Universal Binaries were introduced :/
Notes:
Could you perhaps add an UUID suffix to the symbols? Or the name/path of the module? E g “_llvm.embedded.module. 7464665a-2ce4-11e5-b345-feff819cdc9f”. Then this information would just be discarded by older Xcodes, and not interfere with the arm7/arm64 symbols that the app actually links with.
Comments
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Joachim Bengtsson17-Jul-2015 06:00 PM
And I apologize again: I accidentally enabled bitcode for the simulator build of my library :( My bad! Thanks for rubberducking!
This issue has been verified as resolved and can be closed. Joachim Bengtsson17-Jul-2015 05:55 PM
I apologize: the attached steps to reproduce don't work :( I can't reproduce this in a minimal project outside of my main one. I still can't explain those duplicate symbols, and a google search yields nothing.