which can be made executable. So saving an image is the way to create an executable.
> the people developing it have little or no interest in those features
the demand for these features from the SBCL user base also does not seem high. If it would have been needed, then the development could have been sponsored, like for example the support for Apple Silicon was sponsored by users.
Though other CL implementations provide different deployment options:
ABCL compiles to JVM code.
ECL can compile to C or portable byte code. It also has been used for Android and iOS apps.
LispWorks & Allegro CL have treeshakers and can generate shared libraries. LispWorks also has a runtime for Android and for iOS.
I consider how it arranges that code (the "image" you speak of) to be merely an implementation detail that the user is not concerned with.
The technique of 'tree shaking' was originally developed for lisp.
Neither did sbcl support cross compiling. To the best of my knowledge all you can do with sbcl is save an image.
When I was looking in to this I read through many discussions where the developers appeared hostile to the idea of implementing these features. A common refrain I encountered was that tree shaking is unnecessary because the core images are compressed.
In 2022, removing a few megabytes of data doesn't seem worth the maintenance cost of the feature. In other words, for most users, it's a non-problem.
And assuming he doesn't want what he wants is kind of in bad taste. You don't know his requirements.
Yes, and what exactly constitutes "dead code"? Tree shakers rely on heuristics that can fail in practice. There is provably no way to remove functions from a Lisp image and guarantee your application to work. LispWorks has a "tree shaker", but has umpteen options to tame it so your application doesn't inadvertently break.
Fortunately, it is possible to remove these functions if you, an application developer, so please. Nothing stops you. It's not even difficult. But SBCL has not implemented these (potentially fallible) heuristics for you, because (and only because) an insignificant number of users would find shaving a little binary size off to be valuable at the expense of program correctness.
The kernel supports manual tree shaking: "make menuconfig" and prune away.
I pay for a maintenance contract and licensing for LispWorks that does support tree shaking.
If you need those sorts of features paired with common lisp you could give embeddable common lisp a try. Otherwise if any lisp language will work for you then chicken scheme and gambit scheme both compile to c.