macOS Command Line Tool with Swift Cocoa Framework: Library not loaded

Question

The following error is thrown when trying to run my target:

dyld: Library not loaded: @rpath/libswiftCore.dylib
  Referenced from: x/Xcode/DerivedData/x/Build/Products/Debug/PriorityQueue.framework/Versions/A/PriorityQueue
  Reason: image not found

My target is a Command Line Tool (macOS) written in Swift. I'm using a Cocoa Framework (PriorityQueue) written in Swift. When I set EMBEDDED_CONTENT_CONTAINS_SWIFT to YES on the Framework, the target runs with the following warnings:

objc[99144]: Class _TtC10Foundation15NSSimpleCString is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftFoundation.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtC10Foundation16NSConstantString is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftFoundation.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtC10Foundation15NSFastGenerator is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftFoundation.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCE10FoundationCSo12NSDictionary9Generator is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftFoundation.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs18_EmptyArrayStorage is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs24_ContiguousArrayStorage1 is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs36_NativeSetStorageKeyNSEnumeratorBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs26_NativeSetStorageOwnerBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs18_CocoaSetGenerator is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs43_NativeDictionaryStorageKeyNSEnumeratorBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs33_NativeDictionaryStorageOwnerBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs25_CocoaDictionaryGenerator is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs17NonObjectiveCBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs17_stdlib_AtomicInt is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs19_SwiftNativeNSArray is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs24_SwiftNativeNSDictionary is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs17_SwiftNativeNSSet is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs24_SwiftNativeNSEnumerator is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs31_stdlib_ReturnAutoreleasedDummy is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs20_SwiftNativeNSString is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs19_NSContiguousString is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs40_SwiftNativeNSArrayWithContiguousStorage is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs21_SwiftDeferredNSArray is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs27_ContiguousArrayStorageBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _TtCSs13VaListBuilder is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class SwiftObject is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _SwiftNativeNSArrayBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _SwiftNativeNSDictionaryBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _SwiftNativeNSSetBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _SwiftNativeNSStringBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.
objc[99144]: Class _SwiftNativeNSEnumeratorBase is implemented in both x/PriorityQueue.framework/Versions/A/Frameworks/libswiftCore.dylib and x/MyTargetName. One of the two will be used. Which one is undefined.

And then crashes with (could be unrelated):

MyTargetName[99144:2157492] *** NSForwarding: warning: object 0x1014346a0 of class 'Swift._NSContiguousString' does not implement methodSignatureForSelector: -- trouble ahead
Unrecognized selector -[Swift._NSContiguousString fileSystemRepresentation]

Is this an issue with Xcode that should be reported, or am I missing a setting somehow?

Answer 1

Swift Package Manager sets the following, which resolved this issue for me in another project:

SWIFT_FORCE_DYNAMIC_LINK_STDLIB = YES
SWIFT_FORCE_STATIC_LINK_STDLIB = NO

Note that the search path was set to:

LD_RUNPATH_SEARCH_PATHS = $(TOOLCHAIN_DIR)/usr/lib/swift/macosx @executable_path

Answer 2

In your "Command Line Tool" Target.. set the following...

LD_RUNPATH_SEARCH_PATHS = @executable_path

(Or as Xcode calls them, "Runtime Search Paths") Setting this, the @rpath, in essence, says.. "hey, look in whatever folder the 'tool' is running in" for the dynamically loadable libs. (In this case it will be your build folder.

Other useful @rpath combinations involve similarly relative paths to the executable (which may also be a library or framework binary, in some cases), via @loader_path. Say if the lib was bundled within a framework.. It may require the LD_RUNPATH_SEARCH_PATHS of @loader_path/Frameworks, etc.

Answer 3

The above worked for me. the two user build flags and then setting the following in runtime search paths.

LD_RUNPATH_SEARCH_PATHS = $(TOOLCHAIN_DIR)/usr/lib/swift/macosx @executable_path