dylib-capture-closure

dylib-capture-closure is a utility to analyze a directory recursively for any macOS shared library references pointing outside of that directory, and copy those libraries into the directory, changing the references to point at those new copies.

This allows you to build a tarball or other package from a directory without it depending on shared libraries from (e.g.) /usr/local.

Usage

dylib-capture-closure <STAGE> <PREFIX>

dylib-capture-closure rewrites references under $STAGE, copying in to stage any libraries that are not already within the $STAGE or /usr/lib paths, and rewriting those references. The references are rewritten to the equivalent path under $PREFIX, to support staging changes in one directory ($STAGE) and later installing them to the final ($PREFIX) directory via a package installer, etc.

For example:

Simple case ($STAGE == $PREFIX)

dylib-capture-closure /opt/mything /opt/thing will capture all of the shared library references under $STAGE (/opt/thing), copy them into $STAGE/lib.closure (/opt/thing/lib.closure), and change all the references under $STAGE (/opt/thing) to the corresponding paths under $PREFIX (/opt/thing/lib.closure, in this case, the same paths).

Staging case ($STAGE != $PREFIX)

dylib-capture-closure ~/src/thing/build/stage /opt/thing will capture all of the shared library references under $STAGE (~/src/thing/build/stage), copy them into $STAGE/lib.closure (/opt/thing/lib.closure), and change all the references under $STAGE (~/src/thing/build/stage) to not the copies under $STAGE, but their counterparts under $PREFIX (/opt/thing/lib.closure).

Visually...

Let's say we want to package xdelta3 from homebrew:

$ otool -L /usr/local/bin/xdelta3
/usr/local/bin/xdelta3:
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1238.0.0)
        /usr/local/opt/xz/lib/liblzma.5.dylib (compatibility version 8.0.0, current version 8.2.0)

We can copy this into a new directory...

$ mkdir /tmp/package
$ cp /usr/local/bin/xdelta3 /tmp/package
$ tree /tmp/package
/tmp/package
└── xdelta3

0 directories, 1 file

...then run dylib-capture-closure:

$ dylib-capture-closure /tmp/package /tmp/package
# <...output...>
$ tree /tmp/package
/tmp/package
├── lib.closure
│   └── liblzma.5.dylib
└── xdelta3

1 directory, 2 files

This copied in the library that xdelta3 referenced, and we can see that the binary was changed to point at it:

$ otool -L xdelta3
xdelta3:
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1238.0.0)
        /tmp/package/lib.closure/liblzma.5.dylib (compatibility version 8.0.0, current version 8.2.0)

Caveats

• This is not guaranteed to work perfectly (in fact, it's almost guaranteed to not work perfectly);
• It doesn't copy things from /usr/lib, since these should be the same on all systems;
• It needs XCode and probably some random other things installed.
• Multiple different referred libraries with the same basename will simply clobber each other when imported.