c++ - Conflict between dynamic linking priority in OSX?

Question

There is a dynamic-linking-conflict between different libjpeg dynamic libraries on OSX. First there is a standard native libJPEG.dylib (in /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/). But if you are using MacPorts, you can also have a port-related libjpeg.dylib in (in /opt/local/lib). The latter may for example have been installed as a dependency for some other port.

This creates a problem when you link against your system libJPEG (which is preferred). Then if /opt/local/lib is in DYLD_LIBRARY_PATH, that path will be prioritised when searching for a dynamic lib, resulting in a runtime error when loading symbols:

dyld: Symbol not found: __cg_jpeg_resync_to_restart
 Referenced from:
/System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
 Expected in: /opt/local/lib/libJPEG.dylib
in /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
Trace/BPT trap: 5

So I have two questions (likely related):

1. What is a good way of solving the actual problem (removing /opt/local/lib from DYLD_LIBRARY_PATH obviously solves it but creates problems for other dependencies)?

2. What other paths are searched for dynamic libs (I.e. Where is the "/System/Library" path specified) and why does DYLD_LIBRARY_PATH rank higher priority-wise?

Answer 1

I experienced similar problem while using OpenCV in MacOS El Capitan. Solved the problem using the solution in the link

Solution is to delete some dlylibs in the /usr/local/lib directory and create symbolic links to related files /System/Library/Frameworks/ImageIO.framework/Resources/

cd /usr/local/lib
rm libgif.dylib
ln -s /System/Library/Frameworks/ImageIO.framework/Resources/libGIF.dylib libGIF.dylib
rm libjpeg.dylib
ln -s /System/Library/Frameworks/ImageIO.framework/Resources/libJPEG.dylib libJPEG.dylib
rm libtiff.dylib
ln -s /System/Library/Frameworks/ImageIO.framework/Resources/libTIFF.dylib libTIFF.dylib
rm libpng.dylib
ln -s /System/Library/Frameworks/ImageIO.framework/Resources/libPng.dylib libPng.dylib