Xcode linker error writing Objective-C

Question

A friend of mine asked me to re-write Box2D in objective-c as much as possible. I started writing and when I build the project so far I got, I got some linker errors, I faced similar problem from before, but it didn't help. The error I get is:

Ld /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug/Obj-Box2D normal x86_64
    cd /Users/aizen-qa/Desktop/Obj-Box2D
    setenv MACOSX_DEPLOYMENT_TARGET 10.9
    /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/MacOSX10.9.sdk -L/Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug -F/Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug -filelist /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Obj-Box2D.LinkFileList -mmacosx-version-min=10.9 -fobjc-arc -fobjc-link-runtime -framework Foundation -Xlinker -dependency_info -Xlinker /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Obj-Box2D_dependency_info.dat -o /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug/Obj-Box2D

duplicate symbol _Ob2IsValid in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Mat22.o
duplicate symbol _Ob2InvSqr in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Mat22.o
duplicate symbol _Ob2IsValid in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec2.o
duplicate symbol _Ob2InvSqr in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec2.o
ld: 4 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I've read of similar problems, and tried the solutions such as checking the imports not use .m, and duplicate variable names. But I noticed that the classes of vector have same instance variable names, x, y so is this the reason for the error I'm getting or not?

Well, try doing a clean -- the standard first resort when you get weird errors. — Hot Licks, Jan 04 '14 at 13:09
What have you named your matrix and vector classes (in your port)? — FuzzyBunnySlippers, Jan 04 '14 at 13:09
@NonlinearIdeas matrix Ob2Mat22 and vector Ob2Vec2 and Ob2Vec3 — hakuna matata, Jan 04 '14 at 13:11
Hmmm...don't see how that would be conflicting with anything else...can you post the header/implementation in pastebin (or on SO)? — FuzzyBunnySlippers, Jan 04 '14 at 13:12
Could it be that `Ob2IsValid` ... are defined in a .h-file instead of in the .m file? If the .h file is included by several .m files, you would get duplicate definitions. — Martin R, Jan 04 '14 at 13:12
Have you actually inspected your source files to see where/how _Ob2IsValid et al are declared? Post some examples here. — Hot Licks, Jan 04 '14 at 13:13
@NonlinearIdeas - Please not in pastebin. Edit the question and paste in some excerpts of how the data is defined. — Hot Licks, Jan 04 '14 at 13:14
hmmm...cut/paste error if you copied code from one .m to another for a non-static variable... — FuzzyBunnySlippers, Jan 04 '14 at 13:15
@MartinR yes I defined the function in a .h file, I'll change it and see what I get — hakuna matata, Jan 04 '14 at 13:17
If I read the code right, you have BOOL Ob2IsValid(float32 x) defined in both OBSettings.h AND OB2Math.h. Did I read it right? — FuzzyBunnySlippers, Jan 04 '14 at 13:19
@MartinR It seems its as you said, I made Ob2Math as a class and imported the .h file and the build succeeded. Thanks Martin and everybody for your help — hakuna matata, Jan 04 '14 at 13:32

score 1 · Answer 1 · answered Jan 04 '14 at 13:14

You have data elements being defined, rather than declared, in multiple implementation files. This is usually because of something in an included header.

Look for wherever you reference Ob2InvSqr or Ob2IsValid and make sure that storage for those items is only done once.

score 0 · Answer 2 · answered Jan 04 '14 at 13:14

0

the file Ob2Vec2.o and Ob2Vec3.o contain the same symbol _Ob2InvSqr

very likely that means you have both Ob2Vec2.m and Ob2Vec3.m in the same target.

make sure only one is really compiled

answered Jan 04 '14 at 13:14

Daij-Djan

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score 0 · Answer 3 · answered Jan 04 '14 at 14:08

I guess you have an inline function _Ob2IsValid(...) in one of your header files that isn't being inlined (it's too large?)

If that's the case you can force it to be inlined like this:

__attribute__((always_inline)) inline void MyFunction(...) {}

Or just make it out-of-line

score 0 · Answer 4 · answered Jan 04 '14 at 14:11

0

I was able to solve this thanks to a comment form MartinR. It was because I defined a function in a .h file that I included in multiple Objective-C classes. So what I did was put the function header in the .h file and its implementation in a .m file.

answered Jan 04 '14 at 14:11

hakuna matata

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Xcode linker error writing Objective-C

4 Answers4