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10.11 Coping with intern and find-symbol at runtime

If you want to delete or smash a package, but discover that a symbol is created in it at runtime with intern, or found in it with intern or find-symbol, you have two choices: either change the source to create or manipulate the symbol in another package, or keep the package after all.

If you cannot or do not want to change the source, and the package is large, you face the annoying prospect of having to keep a lot of code in the image for the sake of one symbol created or manipulated at runtime. Fortunately, there are ways to get around this.

The method is to migrate the symbols by hand into new or smaller, "dummy" packages. This is the only working method if at compile time you do not know the names of the symbols to be saved.

Create a special package or packages for the symbols mentioned in these calls, and delete the original packages. When this package is created (with make-package or defpackage), it should use as few of the other packages in the application as possible. Typically, :use nil suffices. For example:

(rename-package "XYZ" "XXX") 
(push "XXX" *delete-packages*) ; discard pkg
(make-package "XYZ" :use nil)  ; new pkg to reference

This allows the real package XYZ to be deleted without breaking a call to intern such as the following:

(intern "FISH" "XYZ")

LispWorks Delivery User Guide - 15 Feb 2015