Whistler – a Lisp that compiles to eBPF

Name: Whistler – a Lisp that compiles to eBPF
Availability: InStock
Author: atgreen

by atgreen·Mar 23, 2026·3 points·0 comments

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AI Analysis

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Replaces LLVM for eBPF with a 5,500-line Common Lisp compiler matching clang optimization.

Strengths

•SSA-based optimizer produces bytecode matching clang -O2 performance without LLVM.
•Automatic CO-RE support preserves struct identity through the compiler pipeline.
•REPL integration allows loading and unloading eBPF code without disk writes.

Weaknesses

•Lisp syntax is a significant barrier for most kernel developers.
•Missing the ecosystem and community support surrounding clang and libbpf.

Post Description

Whistler compiles s-expressions to eBPF bytecode and emits ELF object files (no clang/LLVM). It includes an SSA-based optimizer that matches optimized clang code. You can even use it inline in your Common Lisp code, or from your REPL, and have the eBPF code loaded/unloaded without anything touching disk at all.

Blog post with more background: https://atgreen.github.io/repl-yell/posts/whistler/