iOS app with framework crashed on device, dyld: Library not loaded, Xcode 6 Beta

Question

This crash has been a blocking issue I used the following steps to reproduce the issue:

• Create a Cocoa Touch Framework project
• Add a swift file and a

Answer 1

It is a runtime error that is caused by Dynamic Linker

dyld: Library not loaded: @rpath/...
...
Reason: image not found

The error Library not loaded with @rpath indicates that Dynamic Linker cannot find the binary.

1. Check if the dynamic framework was added to General -> Embedded Binaries

2. Check the @rpath setup between consumer(application) and producer(dynamic framework):

   • Dynamic framework:
     • Build Settings -> Dynamic Library Install Name
   • Application:
     • Build Settings -> Runpath Search Paths
     • Build Phases -> Embed Frameworks -> Destination, Subpath

Dynamic linker

Dynamic Library Install Name(LD_DYLIB_INSTALL_NAME) which is used by loadable bundle(Dynamic framework as a derivative) where dyld come into play
Dynamic Library Install Name - path to binary file(not .framework). Yes, they have the same name, but MyFramework.framework is a packaged bundle with MyFramework binary file and resources inside.
This path to directory can be absolute or relative(e.g. @executable_path, @loader_path, @rpath). Relative path is more preferable because it is changed together with an anchor that is useful when you distribute your bundle as a single directory

absolute path - Framework1 example

//Framework1 Dynamic Library Install Name
/some_path/Framework1.framework/subfolder1

@executable_path

@executable_path - relative to entry binary - Framework2 example
use case: embed a Dynamic framework into an application

//Application bundle(`.app` package) absolute path
/some_path/Application.аpp

//Application binary absolute path 
/some_path/Application.аpp/subfolder1

//Framework2 binary absolute path
/some_path/Application.аpp/Frameworks/Framework2.framework/subfolder1

//Framework2 @executable_path == Application binary absolute path
/some_path/Application.аpp/subfolder1

//Framework2 Dynamic Library Install Name 
@executable_path/../Frameworks/Framework2.framework/subfolder1

//Framework2 binary resolved absolute path by dyld
/some_path/Application.аpp/subfolder1/../Frameworks/Framework2.framework/subfolder1
/some_path/Application.аpp/Frameworks/Framework2.framework/subfolder1

@loader_path

@loader_path - relative to bundle which is an owner of this binary
use case: framework with embedded framework - Framework3_1 with Framework3_2 inside

//Framework3_1 binary absolute path
/some_path/Application.аpp/Frameworks/Framework3_1.framework/subfolder1

//Framework3_2 binary absolute path
/some_path/Application.аpp/Frameworks/Framework3_1.framework/Frameworks/Framework3_2.framework/subfolder1

//Framework3_1 @executable_path == Application binary absolute path
/some_path/Application.аpp/subfolder1

//Framework3_1 @loader_path == Framework3_1 @executable_path
/some_path/Application.аpp/subfolder1

//Framework3_2 @executable_path == Application binary absolute path
/some_path/Application.аpp/subfolder1

//Framework3_2 @loader_path == Framework3_1 binary absolute path
/some_path/Application.аpp/Frameworks/Framework3_1.framework/subfolder1

//Framework3_2 Dynamic Library Install Name 
@loader_path/../Frameworks/Framework3_2.framework/subfolder1

//Framework3_2 binary resolved absolute path by dyld
/some_path/Application.аpp/Frameworks/Framework3_1.framework/subfolder1/../Frameworks/Framework3_2.framework/subfolder1
/some_path/Application.аpp/Frameworks/Framework3_1.framework/Frameworks/Framework3_2.framework/subfolder1

@rpath - Runpath Search Path

Framework2 example

Previously we had to setup a Framework to work with dyld. It is not convenient because the same Framework can not be used with a different configurations

@rpath is a compound concept that relies on outer(Application) and nested(Dynamic framework) parts:

• Application:

  • Runpath Search Paths(LD_RUNPATH_SEARCH_PATHS) - defines a list of templates which be substituted with @rpath.

     @executable_path/../Frameworks
    

  • Review Build Phases -> Embed Frameworks -> Destination, Subpath to be shire where exactly the embed framework is located

• Dynamic Framework:

  • Dynamic Library Install Name(LD_DYLIB_INSTALL_NAME) - point that @rpath is used together with local bundle path to a binary

    @rpath/Framework2.framework/subfolder1
    

//Application Runpath Search Paths
@executable_path/../Frameworks

//Framework2 Dynamic Library Install Name
@rpath/Framework2.framework/subfolder1

//Framework2 binary resolved absolute path by dyld
//Framework2 @rpath is replaced by each element of Application Runpath Search Paths
@executable_path/../Frameworks/Framework2.framework/subfolder1
/some_path/Application.аpp/Frameworks/Framework2.framework/subfolder1

*../ - go to the parent of the current directory

otool - object file displaying tool

//-L print shared libraries used
//Application otool -L
@rpath/Framework2.framework/subfolder1/Framework2

//Framework2 otool -L
@rpath/Framework2.framework/subfolder1/Framework2

//-l print the load commands
//Application otool -l
LC_LOAD_DYLIB
@rpath/Framework2.framework/subfolder1/Framework2

LC_RPATH
@executable_path/../Frameworks

//Framework2 otool -l
LC_ID_DYLIB
@rpath/Framework2.framework/subfolder1/Framework2

install_name_tool change dynamic shared library install names using -rpath

CocoaPods uses use_frameworks![About] to regulate a Dynamic Linker

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