CODEWITHSUNDEEP
cocoacocoapodsclang++
iljawascoding
iljawascoding

Reputation: 1110

CocoaPods: Linking with C++ symbols defined in libPods.a

I recently started working on a podSpec file that integrates levelDB into my projects. (https://github.com/iljaiwas/Podspecs/blob/master/LevelDBPodSpec/0.0.1/leveldb.podspec)

However, when I reference any C++ symbol from a .mm file in the main target, I get a linker error like this:

Undefined symbols for architecture x86_64:
 "leveldb::DB::Open(leveldb::Options const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, leveldb::DB**)", referenced  from:
  -[IHLevelDBContext initWithPath:] in IHLevelDBContext.o

This is what the compiler invocation looks like

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -L/Users/ilja/Library/Developer/Xcode/DerivedData/LevelDBTest2-aiflqgbevhxzfxbrsdamteybrbao/Build/Products/Debug -F/Users/ilja/Library/Developer/Xcode/DerivedData/LevelDBTest2-aiflqgbevhxzfxbrsdamteybrbao/Build/Products/Debug -filelist /Users/ilja/Library/Developer/Xcode/DerivedData/LevelDBTest2-aiflqgbevhxzfxbrsdamteybrbao/Build/Intermediates/LevelDBTest2.build/Debug/LevelDBTest2.build/Objects-normal/x86_64/LevelDBTest2.LinkFileList -mmacosx-version-min=10.7 -ObjC -fobjc-arc -fobjc-link-runtime -stdlib=libc++ -framework Cocoa -lPods -o /Users/ilja/Library/Developer/Xcode/DerivedData/LevelDBTest2-aiflqgbevhxzfxbrsdamteybrbao/Build/Products/Debug/LevelDBTest2.app/Contents/MacOS/LevelDBTest2

From my understanding, the missing ::Open call is included in libPods.a

nm libPods.a | grep "Open"

             U __ZN7leveldb2DB4OpenERKNS_7OptionsERKSsPPS0_
000000000005e5b1 s L___func__._ZN7leveldb6DBImpl24OpenCompactionOutputFileEPNS0_15CompactionStateE
00000000000099d0 T __ZN7leveldb2DB4OpenERKNS_7OptionsERKSsPPS0_
0000000000060ba0 S __ZN7leveldb2DB4OpenERKNS_7OptionsERKSsPPS0_.eh

It seems I can get around the linker errors by changing the "Compiler" setting for the main app from Apple LLVM 4.2 to LLVM GCC 4.2, but this compiler chokes on Objective-C 2.0 features, like this: 

expected a property attribute before 'strong'

Thanks for any pointers on what I might be doing wrong, Ilja

Upvotes: 5

Views: 7182

Answers (2)

anon
anon

Reputation:

You can also set the C++ config settings in the podspec file:

  s.library = 'c++'
  s.xcconfig = {
       'CLANG_CXX_LANGUAGE_STANDARD' => 'c++11',
       'CLANG_CXX_LIBRARY' => 'libc++'
  }

Those settings selects to compile for C++ 2011 and adds the libc++ standard library.

Upvotes: 16

iljawascoding
iljawascoding

Reputation: 1110

The problem went away after I set the "C++ Standard Library" setting in both the application target and CocoaPods target to "compiler default". Seems they were set to incompatible values by default, which caused linker confusion afterwards.

Upvotes: 2

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