Duplicate symbols for architecture x86_64 under Xcode

问题

I now have the same question with above title but have not found the right answer yet. I got the error:

    /Users/nle/Library/Developer/Xcode/DerivedData/TestMoboSDK-Client-cgodalyxmwqzynaxfbbewrooymnq/Build/Intermediates/TestMoboSDK-Client.build/Debug-iphonesimulator/TestMoboSDK-Client.build/Objects-normal/x86_64/MoboSDK.o
    /Users/nle/Library/Developer/Xcode/DerivedData/TestMoboSDK-Client-cgodalyxmwqzynaxfbbewrooymnq/Build/Products/Debug-iphonesimulator/libMoboSDK.a(MoboSDK.o)
duplicate symbol _OBJC_METACLASS_$_MoboSDK in:
    /Users/nle/Library/Developer/Xcode/DerivedData/TestMoboSDK-Client-cgodalyxmwqzynaxfbbewrooymnq/Build/Intermediates/TestMoboSDK-Client.build/Debug-iphonesimulator/TestMoboSDK-Client.build/Objects-normal/x86_64/MoboSDK.o
    /Users/nle/Library/Developer/Xcode/DerivedData/TestMoboSDK-Client-cgodalyxmwqzynaxfbbewrooymnq/Build/Products/Debug-iphonesimulator/libMoboSDK.a(MoboSDK.o)
ld: 75 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Any help is appreciated.

Finally I find out the reason of this error cause I added -ObjC to the Other Linker Flags. After remove this value then I can build my project successfully, but I don\'t know why. Can anyone explain this?

回答1:

75 duplicate symbols for architecture x86_64

Means that you have loaded same functions twice. As the issue disappear after removing -ObjC from Other Linker Flags, this means that this option result that functions loads twice:

from Technical Q&A

This flag causes the linker to load every object file in the library that defines an Objective-C class or category. While this option will typically result in a larger executable (due to additional object code loaded into the application), it will allow the successful creation of effective Objective-C static libraries that contain categories on existing classes.

https://developer.apple.com/library/content/qa/qa1490/_index.html

回答2:

For me, changing 'No Common Blocks' from Yes to No ( under Targets->Build Settings->Apple LLVM - Code Generation ) fixed the problem.

回答3:

Stupid one, but make sure you haven't #imported a .m file by mistake somewhere

回答4:

In my case, I just created a header file to define constant strings like this:

NSString *const AppDescriptionString = @"Healthy is the best way to keep fit";

I solved this scenario by using static:

static NSString *const AppDescriptionString = @"Healthy is the best way to keep fit";

回答5:

I have same problem. In Xcode 7.2 in path Project Target > Build Setting > No Common Blocks, i change it to NO.

回答6:

I found the accepted answer touches on the problem but didn't help me solve it, hopefully this answer will help with this very frustrating issue.

duplicate symbol _OBJC_IVAR_$_BLoginViewController._hud in:

17 duplicate symbols for architecture x86_64

"Means that you have loaded same functions twice. As the issue disappear after removing -ObjC from Other Linker Flags, this means that this option result that functions loads twice:"

In layman's terms this means we have two files in our project with exactly the same name. Maybe you are combining one project into another one? Have a look at the errors above the "duplicate symbols" error to see which folder is duplicated, in my case it was BLoginViewController.

For example, in the image below you can see I have two BImageViewControllers, for me this is what was causing the issue.

As soon as I deleted one then the issue vanished :)

回答7:

Happens also when you declare const variables with same name in different class:

in file Message.m

const int kMessageLength = 36;

@implementation Message

@end

in file Chat.m

const int kMessageLength = 20;

@implementation Chat

@end

回答8:

This occurred on me when I accepted "recommended settings" pop-up on a project that I develop two years ago in Objective-C.

The problem was that when you accepted the "recommended settings" update, Xcode automatically changed or added some build settings, including GCC_NO_COMMON_BLOCKS = YES;.

This made the build failed with the duplicate symbol error in my updated project. So I changed No Common Block to NO in my build settings and the error was gone.

回答9:

Fastest way to find the duplicate is:

Go to Targets
Go to Build Phases
Go to Compile Sources
Delete duplicate files.

回答10:

Remove -ObjC from Other Linker Flags or Please check you imported any .m file instead of .h by mistake.

回答11:

Following steps solved the issue for me.

Go to Build Phases in Target settings.
Go to “Link Binary With Libraries”.
Check if any of the libraries exist twice.
Build again.

回答12:

Defining same variable under @implementation in more than one class also can cause this problem.

回答13:

In my case, there were two file by same name in the location

Targets > Build Phases > Compile Sources and delete any duplicate files.

回答14:

My situation with some legacy project opened in Xcode 7.3 was:

duplicate symbol _SomeEnumState in:

followed with list of two unrelated files.o, then this was repeated couple of times, then finally:

ld: 8 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

What solved it for me was changing enum declaration from:

enum SomeEnumState {
    SomeEnumStateActive = 0,
    SomeEnumStateUsed = 1,
    SomeEnumStateHidden = 2
} SomeEnumState;

to this:

typedef NS_ENUM(NSUInteger, SomeEnumState) {
    SomeEnumStateActive = 0,
    SomeEnumStateUsed = 1,
    SomeEnumStateHidden = 2
};

If somebody has explanation for this, please enlighten me.

回答15:

Go to Targets
Select Build Settings
Search for "No Common Blocks", select it to NO.

It worked for me

回答16:

For me during the Xcode8 recommended project settings update "No Common Blocks" to YES which causes this issue.

回答17:

Make sure you haven't imported a .m file by accident, you might want to delete your derived data in the Projects Window and then build and run again.

回答18:

Today , I got the same error . The error's key word is duplicate. I fix it by:

1. Remove the duplicate file at Build Phases-->Compile Sources
2. If you can not remove it at Build Phases, you need find the file at your project and remove the reference by DELETE :

3. Add the file to your project again
4. Add the file's .m to your Build Phases-->Compile Sources again
5. Build your project, the error will disappear

回答19:

Recently had a headache looking for source of an error. I was wondered, when i found out that my app doesn't want to compile, simply because i had following code snippet in different classes:

dispatch_time_t getDispatchTimeByDate(NSDate *date)
{
    NSTimeInterval interval;
    double second, subsecond;
    struct timespec time;
    dispatch_time_t milestone;


    interval = [date timeIntervalSince1970];
    subsecond = modf(interval, &second);
    time.tv_sec = second;
    time.tv_nsec = subsecond * NSEC_PER_SEC;
    milestone = dispatch_walltime(&time, 0);

    return milestone;
}

Hope that might help someone.

回答20:

I hope it will definitely help you

I got same error 3 duplicate symbols for architecture x86_64

in my case I have copied code from another file of same project eg. code of A.m file to B.m and after complilation i got an error as mention. and i have solve error by changing the name of global Variable.

this error came in my case because of same declare for global variable in both file.

回答21:

I got the same error when I added a pod repository

pod 'SWRevealViewController'

for an already added source code (SWRevealViewController) from gitHub. So, the error will be fixed by either removing the source code or pod repository.

Case # 2:

The 2nd time, this error appeared when I declare a constant in .h file.

NSString * const SomeConstant  = @"SomeValue";
@interface AppDelegate : UIResponder <UIApplicationDelegate> {
...
...

回答22:

For anyone else who is having this issue, I didn't see my resolution in any of these answers.

After having a .pbxproj merge conflict which was manually addressed (albeit poorly), there were duplicate references to individual class files in the .pbxproj. Deleting those from the Project > Build Phases > Compile Sources fixed everything for me.

Hope this helps someone down the line.

回答23:

Similar to Juice007, I had declared and initialized a C type variable in two different .m files (that weren't imported!)

BOOL myVar = NO;

however, this method of declaring and initializing a variable, even in .m, even in @implementation grants it global scope. Your options are:

Declare it as static, to limit the scope to class:
```
static BOOL myVar = NO;
```
Remove the initialization (which will make the two classes share the global var):
```
BOOL myVar;
-(void) init{
    myVar = NO;
}
```
Declare it as a property:
```
@property BOOL myVar;
```

Declare it as a proper iVar in the @interface

@interface myClass(){
    BOOL myVar;
}
@end

回答24:

In my case I had two main() methods defined in my project and removing one solved the issue.

回答25:

Same issue happen with me, when I was integrating the lob project inside my project.

Actually lob project also have the AFNetworking files, So I remove the .m files from lob project.

Actually .m files are conflicting with My project POd/AFNetworking/ .m files

回答26:

In Xcode 6.3.2. I have checked all possibility like as belowed

1: I have not import .m file in my project.

2: Removed -ObjC from Other linker flag.

3: Removed all my derive Data.

still i am getting same error. I have removed this error by removing any variable declaration from .pch file. in my case, i have declared AppDelegate object in .pch file. finally i found reason that cause error. so i remove declaration of any variable from .pch file and my project working charm.

回答27:

Another silly mistake that will cause this error is repeated files. I accidentally copied some files twice. First I went to Targets -> Build Phases -> Compile sources. There I noticed some files on that list twice and their locations.

回答28:

I also have this fault today.That's because I defined a const value in a .m file.But I defined another .m file that also included this const value.That's means it has two same const values.So this error appears. And my solution is adding a keyword "static" before the const value.such as:

static CGFloat const btnConunt = 9;

And then I build the project it won't report this error.

回答29:

1.Go to Build Phases 2.Search for the file name 3.Delete duplicate -> Error will go away.

If it doesn't, try to search for "file.m", if you see any #import "file.m" , clear this line

回答30:

I face the same error what i did

1.Copy the duplicate symbol file (class name or framework name) from the end which is just showed above of the line (duplicate symbols for architecture x86_64).

2. Paste it in Find Navigator and press enter

It showed me duplicate class. I remove the duplicate class and run successfully.

来源：https://stackoverflow.com/questions/24298144/duplicate-symbols-for-architecture-x86-64-under-xcode

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