MacOSX: which dynamic libraries linked by binary?

Question

I have not been able to figure out why my binary is not loading. It is a dylib loaded by MATLAB (MEX-file), and links to quite a few dylibs in different locations. MATLAB tells me it cannot load the MEX-file, but I cannot figure out which of its dependencies it cannot find.

Does anybody have any suggestions for how to debug something like this?

On Linux, ldd is the perfect tool to debug this problem. People keep saying that otool -L is the MacOS equivalent to the Linux ldd, but this is not true. ldd actually looks for the libraries, and tells you which ones can be found, and where they were found. otool -L only tells you what libraries are needed to link against. It does not effort to check to see if they are there. It doesn't even tell you where libraries are searched for when they use @rpath.

otool -l (lowercase L) gives you a dump of the "load commands", there you can see the LC_RPATH commands, which establish where @rpath libraries are searched for. But these have not been able to explain to me which dependency is not found.

Answer 1

Rob Mayoff's answer is a great solution when working with executables. If you find you need to check the runtime dependencies of a dylib, the following script my-ldd may be useful.

#!/usr/bin/env bash 

while getopts "r" OPTION; do
  case $OPTION in   
    r) export DYLD_PRINT_RPATHS=1;;
  esac
done
shift $((OPTIND-1))

cp `which true` .
DYLD_PRINT_LIBRARIES=1 \
DYLD_PRINT_LIBRARIES_POST_LAUNCH=1 \
DYLD_INSERT_LIBRARIES=$1 \
./true
rm ./true

where a the script may be invoked as

my-ldd ./foo.dylib

or (with rpath attempts echo'd)

my-ldd -r ./foo.dylib

Answer 2

Try setting these environment variables before running matlab:

export DYLD_PRINT_LIBRARIES=1
export DYLD_PRINT_LIBRARIES_POST_LAUNCH=1
export DYLD_PRINT_RPATHS=1

Run man dyld for more possibilities.

You can also set the variables for just the matlab command like this:

DYLD_PRINT_LIBRARIES=1 DYLD_PRINT_LIBRARIES_POST_LAUNCH=1 DYLD_PRINT_RPATHS=1 matlab