[ignoreusernames]

You can use a regular common lisp distribution like SBCL and just stick to foreign types https://www.sbcl.org/manual/#Foreign-Types this way you still have a GC for lighter tasks but with the option of manual memory management

[massysett]

You can also use the DYNAMIC-EXTENT declaration to (in general) tell your implementation to stack-allocate a value.

http://clhs.lisp.se/Body/d_dynami.htm#dynamic-extent